I have been trying to figure out whether the TextUML notation for action semantics can be dealt with properly by tools such as Xtext and EMFText (class models and state machines should be fine). For example, given this structural model fragment:

class Advertisement
    attribute summary : String;
    attribute description : String;
    attribute keywords : Keyword[*];
    attribute category : Category;
    operation addKeyword(keywordName : String);
    static operation findByCategoryName(catName : String) : Advertisement[*];
end;

association AdvertisementKeyword
    role Advertisement.keywords;
    role advertisement : Advertisement;
end;

class Keyword specializes Object
    attribute name : String;
end;

class Category specializes Object
    attribute name : String;
    attribute description : String;
end;

association AdvertisementCategory
    role Advertisement.category;
    role ad : Advertisement[*];
end;

Notice the Advertisement class declares two operations. Their behaviour in TextUML could be written as:

    operation Advertisement.addKeyword;
    begin
        var newKeyword : Keyword;
        newKeyword := new Keyword;
        newKeyword.name := keywordName;
        link AdvertisementKeyword(keywords := newKeyword, advertisement := self);
    end;

    operation Advertisement.findByCategoryName;
    begin
        return Advertisement extent.select(
            (a : Advertisement) : Boolean {
                return a->AdvertisementCategory->category.name = catName;
            }
        );
    end;

Note that TextUML allows the behavior to be specified inline when declaring an operation in a class, or in separate, as above (that explains the lack of parameters, modifiers etc).

In the resulting UML model, the behaviour of Advertisement.addKeyword would roughly map to this (using a textual pseudo-notation for UML activities that is hopefully more readable than raw XMI):

activity(name: "addKeyword") {
    structuredActivityNode {
        variable(name: "newKeyword", type: #String)
        writeVariable(variable: #newKeyword, value: createObject(class: #Keyword))
        writeAttribute(
            attribute: #Keyword.name,
            target: readVariable(variable: #newKeyword),
            value: readVariable(variable: #keywordName)
        )
        createLink(
            association: #AdvertisementKeyword,
            end1: #AdvertisementKeyword.keyword,
            end1Value: readVariable(variable: #newKeyword),
            end2: #AdvertisementKeyword.advertisement,
            end2Value: readSelf()
        )
    }
}

and the behaviour Advertisement.findByCategoryName would map to this:

activity(name: "findByCategoryName") {
    structuredActivityNode {
        // implicit variable for return value
        variable(name: "@result", type: #Advertisement, upperBound: *)
        // implicit variable for parameter value
        variable(name: "catName", type: #String)
        writeVariable(
            variable: #@result,
            value: callOperation(
                operation: #Advertisement.select,
                target: readExtent(class: #Advertisement),
                filter: metaValue(#@findByCategoryName_closure1)
            )
        )
    }
}

// a closure is an activity that has a reference to a context activity
closure(name: "@findByCategoryName_closure1") {
        // implicit variable for return value
        variable(name: "@result", type: #Boolean)
        // implicit variable for parameter value
        variable(name: "a", type: #Advertisement)
        writeVariable(
            variable: #@result,
            value: callOperation(
                operation: #Object.equals,
                // variables from the context activity are available here
                target: readVariable(variable: #catName)
                args: readAttribute(attribute: #Category.name, target: readLink(
                    association: #AdvertisementCategory,
                    fedEnd: #Advertisement.ad,
                    fedEndValue: readVariable(variable: #a),
                    readEnd: #Advertisement.category
                ))
            )
        )
}

Note that UML does not have closures, this is an extension to the UML metamodel which I wrote about here before.

Some background on the metaclasses involved: ReadVariableAction, CreateObjectAction, CreateLinkAction, ReadExtentAction etc are all action metaclasses. Actions are the building blocks for modeling activity behaviour in UML.

The million dollar question is: can Xtext and EMFText handle more complex textual notations like this? Is this out of the happy path? Has anyone done something similar? I am under the impression I could use Xtext or EMFText better if I used them based on a intermediate metamodel for behavior that would be closer to the concrete syntax (to get all the IDE bells and whistles for free) and then transformed that to UML in a separate step.

If you have the answers for any of these questions (or even if you have comments and questions of your own), please chime in.

Last Wednesday I attended the Eclipse Modeling Day in Toronto. Coming all the way from Victoria, I must have been the participant that came from farthest. Except, of course, those folks from SAP AG and Itemis that were presenting. But I was really glad to be there. I finally had the chance to chat and discuss about Eclipse and Modeling face to face with people like Simon Kaegi (server-side OSGi), Kenn Hussey (MDT UML2), Eike Stepper (CDO), Ed Merks and (fellow Brazilian) Marcelo Paternostro (EMF), Lynn Gayowski and Ian Skerret (Eclipse Foundation). It’s weird: I have been part of the Eclipse Modeling community since 2006 (and the larger Eclipse community since 2002), but had never actually met any of those folks before. Also amusing was that even though I worked for IBM Ottawa for quite a few years, my first time at the Toronto Lab was many years later as an ex-IBMer living on the West Coast.

The presentations I attended were in general very good. I had seen Ed Merks’ opening presentation on the web before, but this time I could ask questions. I got a better understanding of Xtext (great presentation!), CDO, and the Query, Validation and Transaction frameworks, some technologies I am considering adopting in the near future. I had a first time contact with the Papyrus 2.0 vision, which might provide an opportunity for increasing adoption of the TextUML notation by integrating the TextUML Toolkit into a larger modeling environment. And I liked the idea of a discussion panel at the end.

I had to catch a flight back home that same night, so I could not attend the Eclipse RT Day on the following day nor could I see any of the demos at the DemoCamp. Speaking of which, I did manage to stay long enough to have a beer on the Foundation (thanks!), and chat with Christopher Nagy from Dexterra/Antenna Software, who made a quick ad hoc demo to Ian and myself of their Eclipse/GEF-based tool for authoring multiplatform mobile applications. Very impressive!

As constructive criticism, I do agree with Bjorn that the format could use some tweaking. I sure had to miss some very promising presentations. Maybe with two presentation formats, a longer (for instance, 40-50 mins) and a shorter one (20-25 mins), we wouldn’t need two tracks. I am not sure presenters who came from Europe would have come had they had a shorter slot though. That being said, I was very satisfied with the event overall and am sincerely thankful to IBM Toronto for hosting the event, the Eclipse Foundation for organizing it, all the folks presenting and the companies sponsoring them. Thank you very much! As Lawrence wrote, hope we will see more events like this in the future!

Release 1.4 of the TextUML Toolkit is now available from the update sites, for both Eclipse 3.5+ and 3.4 (by the way, it is possible this will be the last major release targetting Eclipse 3.4, unless someone volunteers to generate and test builds for 3.4).

This is mostly a bug fix release. However, there were some minor notation changes to support stereotypes on dependencies, generalizations and interface realizations, hence the version change from 1.3.x to 1.4.x.

Thanks to Vladimir Sosnin, Attila Bak and fredlaviale for contributing with code and/or bug reports/feature requests. Keep them coming!

As usual, you can find a summary of the changes in the TextUML Toolkit Features page. If you are using the Toolkit, make sure you upgrade soon. If not, what are you waiting for? Install it already!

Last week I did a short presentation on “Model-driven prototyping” for the Vancouver Island Java User Group (VIJUG). It was lots of fun, with good participation from the group. I also showed a quick demo of AlphaSimple, our upcoming service for model-driven prototyping, which seemed to be well received.

For the benefit of those not there, here is a web-version of that presentation, with notes showing on the slides (click here for a full screen view).

Comments are very welcome. I would be very happy to discuss the approach with anyone interested.

The TextUML Toolkit 1.3 is now available, 4.5 months after 1.2. If you already got RC1 (1.3.0.20090614…), it is the same build, no need to upgrade again. Otherwise, just point the Eclipse update mechanism to:

http://abstratt.com/update/ - if you are using Eclipse Galileo, or

http://abstratt.com/update/3.4/ - if you are using Eclipse Ganymede.

Please see the feature page for a summary of the evolution of the TextUML Toolkit in terms of features across releases. Some highlights for this release are better integration with other UML tools and support for both Eclipse 3.4 and 3.5.

As usual, bug reports and feature requests are much appreciated. And if you need help, make sure to ask on the user forum.

The TextUML Toolkit Team

The first release candidate towards version 1.3 of the TextUML Toolkit is now available. The feature overview page has been updated to reflect the changes in the 1.3 cycle.

Please give it a try and report any issues you might find. If no serious problems are found with this build, it will be promoted to 1.3 final later this week.

Note that the main update site supports Eclipse 3.5, but there is also an update site for Eclipse 3.4.  The features are the same, the only differences between the two sites are the dependencies (UML2 3.0 and EMF 2.5 on Eclipse 3.5, UML2 2.2 and EMF 2.4 on Eclipse 3.4).

The TextUML Toolkit team welcomes your feedback.

Wow, it is been more than a month since my last post, but I have been busier than ever working on an upcoming MDD-related product (cannot say much now other than that you will hear more about it here first). However, In TextUML Toolkit-land things are looking pretty exciting.

More hands on deck

Vladimir Sosnin has joined the project and has been on a roll contributing many patches, not only bug fixes but design improvements and features too. It is amazing how quickly he has become very comfortable with the TextUML Toolkit code base (Vladimir is certainly a solid developer, but I’d like to think the quality of the code base helped him too). And if that was not good enough, Vladimir is also using the TextUML Toolkit in his daily work around model-driven development, so that should help ensuring the Toolkit has the features its target audience actually needs.

New release in the making

1.3RC1 should be made available during the weekend. It has some shiny new language features, a bunch of bug fixes, better integration with other UML2 tools and support for both Galileo and Ganymede. By the way, shipping code that can handle different incompatible versions of Eclipse has become a little more challenging with P2, as you cannot ship a feature that has bundles that resolve in a mutually exclusive way - it seems you really need two different features for that.

Documentation moved to SourceForge

SourceForge now has support for MediaWiki, which is used to author and serve the documentation for the TextUML Toolkit. In the spirit of strengthening the message that the project should really be considered a community-based effort, I decided to migrate the documentation from the Abstratt web site over to SourceForge.

I guess that does it, at least for now.  Stay tuned.

I have heard the mantra ‘code is model’ several times. Even though I always thought I got the idea of what it meant, only now I decided to do some research to find out where it came from. Turns out that it originated from a blog post that MS’ Harry Pierson wrote back in 2005. It is a very good read, insightful, and to the point.

The idea that gave title to Harry’s post is that whenever we use a simpler representation to build something that is more complex and detailed than we want to care about, we are creating models. 3GL source code is a model for object code. Byte code is a model for actual CPU-specific executable code. Hence code is model.

He then goes to ask that if we have been successfully reaping the benefits of increased levels of abstraction by using 3GLs for decades now, what prevents us from taking the next step and using even higher level (modeling) languages? He makes several good points that are at the very foundations of true model-driven development:

• “models must be precise“- models must be amenable to automatic transformation. Models that cannot be transformed into running code are “useless as development artifacts“. If you like them for conceiving or communicating ideas, that is fine, but those belong to a totally different category, one that plays a very marginal role in software development, and have nothing to do with model-driven development. Models created using the TextUML Toolkit are forcefully precise, and can include behavior in addition to structure.
• “models must be intrinsic to the development process” - models need to be “first class citizens of the development process” or they will become irrelevant. That means: everything that makes sense to be modeled is modeled, and running code is generated from models without further manual elaboration, i.e., no manually changing generated code and taking it from there. As a rule, you should refrain from reading generated code or limit yourself to reading the API of the code, unless you are investigating a code generation bug. There is nothing really interesting to see there - that is the very reason why you wanted to generate it in the first place. Build, read, and evolve your models! Generated code is object code.
• “models aren’t always graphical” - of course not. I have written about that before here. The TextUML Toolkit is only one of many initiatives that promote textual notations for modeling (and I mean modeling, not diagramming - see next point).
• “explicitly call out models vs. views” - in other words, always keep in mind that diagrams != models. Models are the real thing, diagrams are just views into them. Models can admit an infinite number of notations, be them graphical, textual, tabular etc. Models don’t need notations. We (and tools) do. Unfortunately, most people don’t really get this.

The funny thing is that, most of the times I read someone citing Harry’s mantra, it is misused.

One misinterpretation of the “code is model” mantra is that we don’t need higher-level modeling languages, as current 3GLs are enough to “model” an application. The fact is: 3GLs do not provide an appropriate level of abstraction for most kinds of applications. For example, for enterprise applications, 4GLs are usually more appropriate than 3GLs. Java (EE) or C# are horrible choices, vide the profusion of frameworks to make them workable as languages for enterprise software - they are much better appropriated for writing system software.

Another unfortunate conclusion people often extrapolate from the mantra is that if code is model, model is code, and thus it should always be possible to translate between them in both directions (round-trip engineering). Round-trip engineering goes against the very essence of model-driven development, as source code often loses important information that can only exist in higher level models. The only reason people need RTE is because they use models to start a design and generate code, but then they switch to evolving and maintaining the application by directly manipulating the generated code. That is a big no-no in true model-driven development - it implies models are not precise or complete enough for full code generation.

So, what is your view? How do you interpret the “code is model” mantra?

Even though it has always been possible to open models generated by the TextUML Toolkit in UML2-based diagramming tools, until 1.2 the Toolkit assigned new ids to each element every time a model was regenerated. That meant that any diagrams based on the model being regenerated would become invalid as any cross-references from the diagram to the model would be broken.

Starting with 1.3 M1 (test build available from the milestones update site), the TextUML Toolkit is now better compatible with diagramming tools based on UML2. You can edit the source in TextUML and save it to cause model generation to occur, and any existing diagrams should still remain valid.

Here you can see the TextUML Toolkit being used side-by-side with the UML2 Tools graphical editor:

Actually, I found out that UML2 Tools can be a great companion for the TextUML Toolkit because it seems to just do the right thing when it notices the underlying model has been changed externally: new elements show up, removed elements disappear, preserved elements preserve their layout. I tried doing the same with Papyrus 1.11 and unfortunately it does not seem to handle external updates properly. I haven’t tried with other UML2-based diagram editors, so at this point I am not sure which one represents the trend here.

I have been doing some exploratory work around running the TextUML Toolkit’s compiler as a standalone Java application. In other words, without OSGi. You Eclipse/OSGi heads out there might ask: why would anyone want to do that? The answer is: enhanced applicability. Severing ties with the Eclipse runtime/OSGi means the compiler would become usable in other contexts, and by more people. Think Ant or Maven-driven builds, or (the horror!) other IDEs.

The TextUML compiler’s dependencies

The TextUML compiler is not very different from any ordinary 3GL compiler. It reads a bunch of source files and spits another bunch of object files. For reading and writing files, the TextUML compiler uses EFS, the Eclipse File System. For generating the object files, which are UML models, the compiler uses UML2 and EMF.

Luckily, all these components are expected to work on a standalone application, although some restrictions in functionality might apply. At a first glance, one would expect that running the TextUML compiler without OSGi should be quite feasible. But, as I should have learned by now, it is never that simple…

Extension registry without OSGi

The TextUML compiler, and some of its dependencies use the extension registry to receive contributions to their extension points or make contributions to other components’ extension points. Since Eclipse 3.2, the extension registry API provides support for creating registries without OSGi. Basically, you can add any extension and extension points you want, all you need to do is to provide the XML markup for them.

Problem: in a standalone Java application, it is the application’s responsibility to somehow find the plugin manifests and populate the extension registry.

Solution: I started with the example Paul Webster posted on the platform newsgroup almost two years ago. It basically starts from a file system location which it assumes to hold plugins, both on JAR’d and directory form. It will find plugin manifests (plugin.xml), recognize translation resources (plugin.properties), and even discover the bundle name by parsing the bundle manifest (MANIFEST.MF), and use that to populate the extension registry. Pretty cool, thanks PW. I just cleaned-up the code a bit and enhanced it to also find plugin manifests using the application’s classloader. I also had to add support for setting the default extension registry, which is the one other components will get when invoking Platform.getExtensionRegistry() or RegistryFactory.getRegistry(). Finally, I had to implement basic support for creating executable extensions, which was not too hard given that I could assume the entire application is using the same (application) classloader.

EFS without OSGi

Also since 3.2, the Eclipse File System does not require OSGi to operate, however it does require a functional registry as it uses an extension point to allow file system implementations to be plugged in. So, provided one manages to populate the default extension registry, EFS works fine on a standard Java app. No action required here (yay!).

EMF and UML2 without OSGi

EMF has long been advertised as being mostly functional when running in non-managed mode. However, when running in an standalone app, EMF does not process extensions to its extension points (such as resource factories, metamodel packages and URI mappings), so a standard Java application needs to explicitly initialize EMF, which is clearly suboptimal.  That is because EMF only processes contributions to its extension points right during bundle activation. There is no alternative way to trigger processing of the registry (see bug #271253), which sucks, given that the registry is there just waiting to be used. With no OSGi, there is no such thing as bundle activation, and thus EMF goes into autistic mode. This is also true for UML2 (not surprisingly, as they share many implementation traits), the main difference being that UML2’s extension points are much less used than EMF’s.

Problem: Ecore won’t process the extension registry when running in a standalone Java application.

Solution: Change Ecore so it allows clients to explicitly trigger processing of the contributions to Ecore’s extension points. My local hacky solution was to make Ecore’s extension registry parsers to be publicly visible so any client could invoke them.

‘platform:’ URLs without Equinox

Extensions to Ecore’s URI mapping extension often translate to ‘platform:’ URLs, which are another common Eclipse-ism, and thus not supported in plain Java applications.

Problem: No support for ‘platform:’ URL schemes  in standalone mode.

Solution: I implemented a simple URL stream handler for the ‘platform’ protocol. The current implementation complete ignores the path component that determines what bundle the resource is in. That is clearly something that needs to be improved, but should not be too hard.

Conclusion

Well, it wasn’t really a walk in the park, but other than the issue that requires a change in EMF (bug #271253, which I am hoping could be addressed for Ganymede Galileo),  I am pretty happy with the results of this exploration.

I made all the code I wrote (including my version of Paul Webster’s registry loader) available on the TextUML Toolkit’s SVN repository on SourceForge. Feel free to use it and submit improvements. I wonder if this sort of stuff could find a home in Eclipse.org, as I think many people currently developing for non-OSGi targets would like to take advantage of some great OSGi-agnostic Eclipse APIs.

I decided it was time to start using Eclipse 3.5 before it went RC or else if I find any blockers there won’t be time left for them to get fixed before the next release this Summer. I have been on the other side of the fence and know how frustrating it is when people only really start reporting bugs at the very end of the release cycle.

After I installed the 3.5 M6 SDK, I decided to install the TextUML Toolkit 1.2…

Nothing to install?

First surprise: no features would show on the update site! WTH? Well, turns out I had the Update UI to show available features grouped by category, but the TextUML Toolkit update site does not use categories. Unchecking the option to group by categories shows the four features in the TextUML Toolkit update site as it was usual in 3.4. Phew… I was just about to enter a bug report against the Eclipse update component (a.k.a. p2), when I found out that that unintuitive UI behavior has been recently addressed and the next milestone won’t show this problem any longer.

A roadblock

I managed to install the TextUML Toolkit, and that brought along EMF and UML2, which are required features. Since, at this time, the TextUML Toolkit does not specify version range for its dependencies, the latest versions of EMF and UML2 were automatically installed by Eclipse. That should be fine, I thought, as one of the Eclipse development key mandates has always been backward compatibility. But this time around that was not the case: the TextUML builder was failing to compile a TextUML source file that was making use of template parameters. Turns out the UML2 API around templates has changed in its version 3.0. Before (in UML2 2.2), a template parameter substitution could have multiple formal and actual parameters. Now it can have only one of each, and thus the TextUML Toolkit is (partially) broken in 3.5.

So much for core values, you might be thinking? Well, to be fair, this is a bit of a fringe case. The UML2 API is an Eclipse component, and as such should strive for backward compatibility too. However, it is also a high-fidelity rendition of the UML specification published by the OMG. In this case, the OMG fixed a bug (#9838) in the spec, and as often is the case with UML, that resulted in a change that was not backward compatible. If the OMG promotes changes that are not backward compatible, the UML2 team does not have much of a choice: in order to continue to closely implement the spec, it has to break the Eclipse guidelines.

And neither do I. For the TextUML Toolkit 1.2, I will have to issue a maintenance release (1.2.1) that will explicitly depend on UML2 2.2, thus avoiding the new version, and probably becoming incompatible with other UML modeling packages that only run on Galileo and UML2 3.0. For the next release of the TextUML Toolkit (1.3), I will have to adopt the new API and explicitly depend on UML 2 3.0.

That is how life goes… for some reason, I kind of feel like a flea crawling on the back of an elephant.

I strongly believe queries are an essential part of a domain model. As such, in our quest to have (UML) models that can fully (yet abstractly) describe object models for the common enterprise applications, we cannot leave out first class support for queries.

But how do you do queries in UML? The obvious answer seems to be OCL, but that is not the approach I am taking as OCL and UML have serious interoperability/duplication issues. Instead, I took the  middleweight extension approach.

First, we model a protocol for manipulating collections of objects (showing only a subset here):

class Collection specializes Basic
  operation includes(object : T) : Boolean;
  operation isEmpty() : Boolean;
  operation size() : Integer;
  operation exists(predicate : {(:T) : Boolean}) : Boolean;
  operation \any(predicate : {(:T) : Boolean}) : T;
  operation select(filter : {(:T) : Boolean}) : T[*];
  operation collect(mapping : {(:T) : any}) : any[*];
  operation forEach(predicate : {(:T)});
  operation union(another : T[*]) : T[*];
  (…)
end;

That protocol is available against any collection of objects, which in UML can be obtained by navigating an association, reading an attribute, invoking an operation, obtaining the extent of a class (remember Smalltalk’s allInstances), anything where the resulting value has multiplicity greater than one.

Note most of the operations in the Collection protocol take blocks/closures as arguments. Closures are used in this context to define the filtering criterion for a select, or the mapping function for a collect.

For instance, for obtaining all accounts that currently do not have sufficient funds, this method would do it:

static operation findNSFAccounts() : Account[*];
begin
    return Account extent.select(
        (a : Account) : Boolean {return a.balance < 0}
    );
end;

Note the starting collection is the extent of the Account class. That is very similar to what is done in the context of query languages for object-oriented databases, such as OQL or JDOQL. We then filter the class extent by selecting only those accounts that have a negative balance, by passing a block to the select operation.

When mapping that behavior to SQL, we could end up with a query like this:

select _account_.* from Account _account_ where _account_.balance < 0

Another example: we want to obtain all customers with a balance above a given amount, let’s say, to send them a letter to thank them for their business. The following method specifies that logic:

static operation findBestCustomers(minBalance : Real) : Customer[*];
begin
    return (Account extent.select(
          (a : Account) : Boolean { return a.balance >= minBalance }
    ).collect(
          (a : Account) : Customer { return a->AccountOwner->owner }
    ) as Customer);
end;

Note that we start off with the extent of Account class, filter it down to the accounts with good balance using select, and then map from that collection to a collection with the respective account owners by traversing an association using collect.

If that was going to be mapped to SQL, one possible mapping would be:

select _customer_.* from Account _account_
    inner join Customer _customer_
        on  _account_._accountID_ = _customer_._customerID_
    where _account_.balance >= ?

Much of this can be already modeled if you try it out with the TextUML Toolkit 1.2. But, you might ask, once you model that, what can you do with UML models containing queries like the ones shown here?

Since the models are complete (include structure and behavior), you can:

1. Execute them. Imagine writing automated tests against your models, or letting your customer play with them before you actually start working on the implementation.
2. Generate complete code. The generated code will include even your custom queries, not only those basic ones (findAll, findByPK) code generators can usually produce for you.

If you would like to see tools that support that vision, keep watching this blog.

So, what is your opinion?
Do you see value in being able to specify queries in your models? Is this the right direction? What would you do differently?

The TextUML Toolkit 1.2 is now available, 5 months after 1.1, when it first became an open source project. If you already got RC2 (1.2.0.200902011417), it is the same build, no need to upgrade again. Otherwise, just point the Eclipse update mechanism to:

http://abstratt.com/update/

Please see the feature page for a summary of the evolution of the TextUML Toolkit in terms of features across releases.

As usual, bug reports and feature requests are dearly appreciated. And if you need help, make sure to ask on the forum.

Acceleo is a cool open-source code generation tool that has great integration with the Eclipse IDE and EMF-based metamodels. The tool has a strong emphasis on simplicity and ease of use, which, for an open source development tool, is really a breeze of fresh air.

The Acceleo website includes a repository of code generation modules, which are extensions to the tool that target generation for specific platform/languages, such as .Net (C#/NHibernate), Java (Hibernate/Struts/Spring), Python, PHP, C, Zope etc. Of course, you can also develop your own modules, using Acceleo template editors with metamodel-driven content assist, and live sample generation.

Most of the modules in the Acceleo repository take UML2 compatible models. That means you can use the TextUML Toolkit for quickly creating your UML models using the TextUML textual notation, and then use Acceleo to generate code from them.

One of the most mature code generation modules in the Acceleo repository is the UML2 to Java EE module, which can generate code for Spring, Struts and Hibernate-based Java applications from UML2 models. A step-by-step guide would be too much for this post, but if you want to explore generating Java EE code from UML models you create using the TextUML Toolkit, here are some pointers:

Get the tools. First of all, using Eclipse 3.4, install all features from the following update sites:

• TextUML Toolkit - http://abstratt.com/update/
• Acceleo code generator - http://acceleo.org/update/
• Acceleo code generation modules - http://acceleo.org/modules/update

Once the install is complete, allow Eclipse to restart for the new plug-ins to become available.

Create your UML models and profiles. Create a project for your UML models using the TextUML Toolkit. For an example of how to do that, see the TextUML Tutorial. You will need to define in your model project a profile where you declare the stereotypes that you will use to annotate your modeled classes, to drive code generation (see how here)

Create your Acceleo generator project. The Acceleo website has plenty of documentation on how to create Acceleo code generation projects. Some pointers:

• main documentation page (instalation and tutorials)
  
• UML to JEE module documentation
  

Note that this module has a bug in which it is based on a profile with an invalid UML name which won’t work with the TextUML Toolkit out of the box. Instead of using the profile shipped with that module, you can then override the default profile and stereotypes using a properties file at the root of your generator project as shown here so to direct it to your own profile and stereotypes. You can also find a more structured guide for using Acceleo and the TextUML Toolkit together here. Even though that tutorial uses a customized version of the JEE module, it can still be helpful.

As usual. If you need help generating code from UML models using the TextUML Toolkit and Acceleo, feel free to ask for help here, or in the user forum.

A new RC build of the TextUML Toolkit is now available. It has one bug fix since RC1. Basically, when rendering stereotypes, the metaclasses extended by the stereotype were not being shown. Not really critical, but isolated and safe enough to be fixed now. Pending any last minute bug reports by the community, it is likely this build will be promoted to 1.2 release early this week.

Also, while testing, I noticed that the Pet Store example was triggering a known Graphviz issue with associations navigable both ends, so I updated the petstore_models project so the relationship between Title and Payment was navigable only in one direction (Title -> Payment). I recaptured the class diagram images showing on that page using the Image Viewer “Save to File” function instead of screenshot sections.

Just trigger a software update for the TextUML Toolkit to get RC2.

Yikes, it happened again. A user reported that the TextUML Toolkit 1.2 RC0 build announced earlier this week wouldn’t run on Java 5 VMs (Mac users would be the most affected). This has just been fixed (one bundle was being compiled against Java 6) and a new release candidate is now available from the update site. If you too were seeing “java.lang.UnsupportedClassVersionErrors” running RC0, just go ahead and update to RC1.

The third milestone build and first release candidate of the TextUML Toolkit, the IDE for textual UML  modeling, is now available from the update site.

The feature page shows all the new features in this new release, but here they are:

• primitive types
• data types (a.k.a. structs)
• required extensions for prototypes
• behaviour modeling (a.k.a. action semantics)
• shorthand notation for aggregation and composition
• abstract stereotypes
• cross-project references

As you can tell, most of the work in the 1.2 release cycle was towards extending the TextUML notation with support for UML.

There were also several bug fixes, one of them being the first to be addressed by an external contributor (thanks, Massimiliano!).

If no serious issues are found with this milestone build, it will be promoted to 1.2 final by the next weekend. So, if you are using a 1.1.* build, make sure you upgrade it to a 1.2 release candidate build and start smoke testing with your usual workflows, and report any bugs you find.

UML is known to be a huge language, and that has two problems: it is too complex, having way more features than most applications will ever need, and can still be insufficient, as no single language will ever cover everybody’s needs.

In the article “Customizing UML: Which Technique is Right for You?”, James Bruck and Kenn Hussey (both from the UML2 team) do a great job at covering the several options for extending (or restricting) UML (James also made a related presentation at last year’s EclipseCon, together with Christian Damus, of Eclipse OCL fame). Cutting to the chase, these are the options they identify:

• using keywords (featherweight extensions)
• using profiles, stereotypes and properties/tagged values (lightweight extensions)
• extending the metamodel by specializing the existing metaclasses (middleweight extensions)
• using package merges to select the parts of UML you need (heavyweight extensions)

Each option has its own strengths and weaknesses, as you can see in the referred article/presentation. At this time, the TextUML notation supports two of those approaches: profiles and metamodel extensions.

Adding closures to UML

Even though profiles are the most popular (and recommended) mechanism for extending UML, it is not enough in some cases/applications. That has been the case in the TextUML Toolkit, for instance, when implementing closures in the TextUML action language (yes, the Toolkit eats its own dog food).

According to the wikipedia entry, “a closure is a function that is evaluated in an environment containing one or more bound variables. When called, the function can access these variables. ”

It really makes sense to (meta) model a closure as some kind of UML activity, which is basically a piece of behavior that can be fully specified in UML. Methods, for instance, are better modeled in UML as activities. Activities are composed of activity nodes and actions, which are similar to blocks of code and instructions, respectively.

The only thing that is missing in the standard Activity metaclass is the ability for a closure to have an activity node from another activity as context, so it can access context’s local variables. So here is a possible (meta) modeling of closures in UML using the TextUML syntax:

[Standard::Metamodel]
model meta;

apply Standard;

(*
  A closure is a special kind of activity that has another
  activity’s activity node as context. A closure might
  reference variables declared in the context activity node.
*)
[Standard::Metaclass]
class Closure specializes uml::Activity
  (* The activity node that provides context to this closure. *)
  reference contextNode : uml::StructuredActivityNode;
end;

end.

Or, for those of you who prefer a class diagram (courtesy of the EclipseGraphviz integration):

Note a model contributing language extensions must be applied the Standard::Metamodel stereotype, and each metaclass must be assigned the stereotype Standard::Metaclass.

Of course, there is no point in being able to metamodel closures, if there is no way to refer to them. We need a kind of type that we can use to declare variables and parameters that can hold references to closures. That also means we need to be able to invoke/dereference a closure reference, and there is no support for referring to metamodel elements in the UML action language. That means we need more language extensions. But I will leave that to another post. My goal here was to show how simple it is to create a simple UML metamodel extension with the TextUML Toolkit.

What about you, have you ever needed to extend UML using a metamodel extension? What for?

No tool is an island. That is even more important when we are talking about highly focused single-purpose tools such as the TextUML Toolkit. As you probably know, the TextUML Toolkit is a tool for UML modeling using a textual notation, but that is about it. The TextUML Toolkit itself won’t help if you need features such as code generation, reverse engineering or graphical modeling/visualization. That might look as a negative thing to some, but that is by design. I am a strong believer of separation of concerns, component-based software and using the best tool for the job, and that is reflected in the design of the Toolkit.

This post will describe how to use models created by other UML2-compatible modeling tools from models you create using the TextUML Toolkit. I plan to cover other areas of integration in future posts.

Reading models created by other UML tools using the TextUML notation

If you have the TextUML Toolkit installed, one of the editors available for UML files is the TextUML Viewer. As the name implies, it is not really an editor, i.e., you cannot edit models with it, just visualize them using the TextUML notation. But it is an useful tool for reading UML models you don’t have the source for, i.e. models created by other UML2 modeling tools.

Using models created by other tools…

There are a few different ways of using models created by other UML modeling tools from your models created in TextUML.

…by co-location

In this method, you just drop the UML model you want to use to at the root of your TextUML (i.e. MDD) project. All models at the root of the same MDD project are considered to be in the same repository and thus you can make cross-model references by either using qualified names or importing the package and using simple names.

This method is dirty simple, but it forces you to keep the foreign model at a specific location, potentially forcing you to keep multiple copies of the model.

…with project references

In this method (available starting in version 1.2), the UML model you want to use is in a different project than the one you want to refer it from. You just open the properties dialog for your TextUML (MDD) project and add the project providing the UML model you want to use to the list of referenced projects. Now models at the root of that project will also be visible from your TextUML (MDD) project, in other words, they are also seen as part of the same repository.

This method is more powerful than the previous one, as now models can be shared by reference instead of by copying. There is a limitation still: the models you use ought to be part of some project in the workspace, so you cannot refer to models stored at arbitrary locations in the file system or models that are contributed by Eclipse bundles.

…by explicitly loading them

For this method, you use the load directive to load an external model located by a URI.

This method allows you to load any model, provided its location can be represented as a resolvable URI. That is the case of any file system path, or Eclipse platform URLs. The caveat is that some URIs such as file system URIs are not portable, so they are are bound to be invalid on other machines.

The entire truth…

…is that even if you are using only the TextUML Toolkit for building UML models, these are the same mechanisms for creating models that make cross-package references (see also the TextUML Guide). For the TextUML Toolkit, all UML2-compatible models are equal, no matter how they were created.

The second milestone build towards TextUML Toolkit release 1.2 is now available from the milestone update site. Get it while it is hot.

This milestone adds support for some UML language features:

• required extensions for stereotypes
• data types
• primitive types

But what is really exciting is that this milestone is also the first build that includes a contribution from a new member of the TextUML Toolkit team: Massimiliano Federici provided a  patch that squished bug 2127735 (revision 194). Kudos to Massimiliano, his contribution was greatly appreciated, and it seems it might just be the first of many!

Yesterday I checked in support for UML primitive types in the TextUML Toolkit. As an example of the syntax, here is the UMLPrimitiveTypes model, shipped in Eclipse UML2, rendered by the TextUML Source viewer:

[Standard::ModelLibrary]
model UMLPrimitiveTypes;

apply Standard;

primitive Boolean;

primitive Integer;

primitive String;

primitive UnlimitedNatural;

end.

As you can see, primitive types are declared using the keyword ‘primitive’, and cannot specialize other types or have structural features (thus there is no ‘end’ terminating the type declaration). To be honest, I am not sure this is the intended semantics, as the UML specification does not seem to explicitly disallow that.

Here is the breakdown of the change sets (r188-191):

• automated tests (r190)
• parser and model generation (r191)
• textual renderer (r189)
• editor (r188)

To be frank, the only test case added was quite trivial:

public void testPrimitiveType() throws CoreException {
  String source = "";
  source += "model someModel;\n";
  source += "primitive Primitive1;\n";
  source += "end.";
  parseAndCheck(source);
  PrimitiveType found = (PrimitiveType) getRepository().findNamedElement(
    "someModel::Primitive1", IRepository.PACKAGE.getPrimitiveType(), null
  );
  assertNotNull(found);
}

But it is a good start. It ensures parsing works, and the model generated has the intended element created under the right parent package.

Any suggestions of what UML feature to cover next? And what is your take? Can UML primitive types have structural features or specialize other types/implement interfaces?

(By the way, if you want to understand how the TextUML Toolkit is implemented, feature posts like this are a good starting point)

Just checked in a new feature in the TextUML Toolkit: support for data types (a.k.a. structs). This is an example of a data type declaration:

datatype UserName
  attribute firstName : String;
  attribute lastName : String;
end;

You can declare operations and specialize other classifiers as usual.

Change set

Here are the individual changes per plug-in (r177-r186):

• automated tests (180 and 185)
• parser and model generation (181, 184 and 186)
• textual renderer
• editor

There, nice and easy. Well, actually, I ended up doing a second commit because I forgot to ensure a data type specializes only other data types. But now that has been taken care of.

As usual, suggestions of UML features to support in the TextUML Toolkit are most welcome.

Great discussion over @ Slashdot: Is Open Source Software a Race To Zero?

I really think the open source approach has lots of benefits, for the software itself and all parties involved. However, I would say it will probably take a decade before sound business models based on open source are really understood and start to become mainstream.

At this point in time, (as most people) I still think it is considerably harder/trickier to make money developing software as open source than it is with closed source. At least for small companies. A few reasons:

• reduced barrier to entry for new competitors as they can easily leverage the fruits of your hard work. Even more so if you choose a more liberal license such as a BSD, EPL or Apache (JBoss and MySQL use GPL, for instance).
• lower profit margins, if you decide to adopt a services-based business model instead of one based on selling product licenses, which is a common approach.
• the overhead of maintaining the open source software while developing the closed source extensions or providing the related services, the very activities that will actually make money, could be unbearable.

The TextUML Toolkit is open source (EPL) since release 1.1. The decision of making the TextUML Toolkit open source was based on the fact that I (a.k.a. Abstratt Technologies) never intended to make any money directly off of it, wanted to attract external contributions and maybe get some visibility to other future offerings. But I wouldn’t have done it if I had any plans of selling the TextUML Toolkit as a product on its own.

Well, I am interested in your thoughts. Do you know of cases of small companies making good money from developing and selling open source software (using liberal licenses such as the EPL)?

I would like to see the TextUML Toolkit as an Eclipse MDT subproject. Not long ago, I talked to Kenn Hussey and Ed Merks (they lead the UML2 and EMF projects, respectively) about the idea of proposing the Toolkit to the EMO and they both liked it (Ed actually suggested the idea in the first place). However, I was concerned that just one guy (yours truly) working on the project on and off in his spare time with no user community didn’t look very promising, and Kenn promptly agreed, so it was decided that it was important to get other people on board first.

With the intent of starting to gather some sort of community and hopefully contributors, I decided to release version 1.1 as EPL. In the first couple of weeks after that, I noticed a significant spike in interest (page hits, issues opened, forum activity). But then everything went back to how it was before: today, there is no evidence anybody is using the tool, and I am still the only committer in the project.

So, this is a call (or a cry) for contributors: if you like the textual approach to UML modeling proposed by the TextUML Toolkit, would like to help putting together a proposal, and have some amount of time/resources to commit to the project in the long(ish) run, I am really eager to hear from you.

Things that are in scope for the project:

• broader notation coverage of UML features
• richer IDE support: content assist, search/hyperlinking, refactoring
• better integration with graphical UML tools

If you are interested, feel free to contact me via this blog, the Toolkit forum or e-mail (rafael at abstratt.com).

Just checked in a new feature in the TextUML Toolkit: required extensions for stereotypes (honestly, I didn’t know about that feature in UML until I read this post on the Eclipse UML2 newsgroup).

The following is a stereotype extending two metaclasses (uml::Class and uml::Operation):

profile my_profile;

import uml;

stereotype foo extends Class, Operation required
end;

end.

In the example above, the extension of Operation is required, the extension of Class is not.

Change set

The change set to implement required extensions in the TextUML Toolkit (issue #2266268) was quite small (btw, kudos to the UML2 project for providing the best API for UML out there).

Here are the individual changes per plug-in (r153-r156):

• automated tests
• parser and model generation
• textual renderer
• editor

Any other UML feature you would like to see exposed in the TextUML notation? Suggestions are welcome.

The first milestone build of the next TextUML Toolkit release is now available from the milestone update site. This preview build is the first to include support for modeling behavior using action semantics. I hinted at this capability here before, and I plan to cover action semantics in the TextUML notation in following posts. But most people will get the gist of the notation from the examples below:

Here is an example of a UML model of an Account class represented in TextUML:

model bank;

import base;

class Account
    attribute accountNumber : String;
    attribute balance : Integer;

    operation withdraw(amount : Integer);
    begin
        self.balance := self.balance - amount;
    end;    

    operation deposit(amount : Integer);
    begin
        self.balance := self.balance + amount;
    end;

    static operation newAccount(number : String,owner : Client): Account;
    begin
        var newAccount : Account;
        newAccount := new Account;
        newAccount.accountNumber := number;
        newAccount.balance := 0;
        link ClientAccount(owner := owner, accounts := newAccount);
        return newAccount;
    end;
end;

class Client specializes Object
    attribute name : String;
    static operation newClient(name : String): Client;
    begin
        var newClient : Client;
        newClient := new Client;
        newClient.name := name;
        return newClient;
    end;
end;

association ClientAccount
    navigable role owner : Client[1];
    navigable role accounts : Account[0, *];
end;

end.

And here an example of a test driver ‘program’ (note the use of a closure for looping through a collection of objects):

package test;

apply base_profile;

import bank;
import base;

class TestDriver
  [entryPoint]
  static operation run();
  begin
      var john : Client, mary : Client,
             account1 : Account, account2 : Account, account3 : Account;
      john := Client#newClient(”John Doe”);
      mary := Client#newClient(”Mary Doe”);

      Console#writeln(”Created: “.concat(john.name));

      account1 := Account#newAccount(”1234-1″, john);
      account2 := Account#newAccount(”1238-2″, mary);
      account3 := Account#newAccount(”2231-7″, john);

      Console#writeln(”account owner: “.concat(account1->ClientAccount->owner.name));
      Console#writeln(”account number: “.concat(account1.accountNumber));
      Console#writeln(”initial balance is: “.concat(account1.balance.toString()));

      account1.deposit(2000);
      Console#writeln(”after deposit, balance is: “.concat(account1.balance.toString()));

      account1.withdraw(500);
      Console#writeln(”after withdrawal, balance is: “.concat(account1.balance.toString()));

       /* Now show information for all accounts. */
  	Account extent.forEach(
          (a : Account) {
              Console#writeln(”*******”);
              Console#writeln(”Owner: “.concat(a->ClientAccount->owner.name));
              Console#writeln(”Number: “.concat(a.accountNumber));
              Console#writeln(”Balance: “.concat(a.balance.toString()));
          }
      );
  end;
end;

end.

And here is the output of the test driver program, produced by running it on the Libra UML runtime (not part of the TextUML Toolkit):

Created: John Doe
account owner: John Doe
account number: 1234-1
initial balance is: 0
after deposit, balance is: 2000
after withdrawal, balance is: 1500
*******
Owner: Mary Doe
Number: 1238-2
Balance: 0
*******
Owner: John Doe
Number: 1234-1
Balance: 1500
*******
Owner: John Doe
Number: 2231-7
Balance: 0

Alternatively, one could have generated 100% of the code for a target platform of choice, given that all the information necessary for that is in the model. Note that code generation is not part of the TextUML Toolkit.

Do you want to give it a try? Install M1 from the milestone update site. You can also fetch the example projects from here.

It is certainly a rough stone. I am counting on the community feedback to figure out what areas need to be smoothed first. Please provide your feedback or ask questions on the TextUML Toolkit forums.

Do you know what UML can do for you? I mean, did you know that UML models can actually do things?

One of the least known features of UML is that you can model detailed imperative behavior. The UML “instruction set” can do things like:

• create and destroy objects
• create and destroy links (associations) between objects
• read and write attributes and local variables
• invoke operations and functions
• throw and catch exceptions
• conditional statements
• loops

That is quite amazing, isn’t? And all that while still preserving a high level of abstraction. Such capability is generally referred to as ‘action semantics’. Action semantics provides the basic framework for executability in UML and has been there for quite a while now. It was originally added to the spec, first as patch, in UML 1.5 (2003), and then more seamlessly integrated into UML 2.0 and following spec releases.

Action Semantics and TextUML

An even more well-kept secret is that the TextUML notation supports UML action semantics and thus the creation of fully executable UML models. This support is not yet shipped as part of the TextUML Toolkit, but will be in the next release. Meanwhile, if you want to give it a try or take a closer look, you will have to grab the source from the SVN repository.

I plan to go into more details in the near future, but just to wet your appetite, here is one example of an executable UML model described in the TextUML notation:

package hello;

apply base_profile;
import base;

class HelloWorld
    [entryPoint]
    static operation hello();
    begin
        Console#writeln(”Hello, World”);
    end;
end;

end.

Cool, isn’t? If you had a UML runtime, this model could be executed even before you made a decision about what platform to target. Also, if your code generator were action semantics aware, you could trigger code generation for the target platform(s) of choice, with the key difference that you could achieve (or get very close) to full code generation, as the model now also describes behavior. No more of that monkey business of having to edit the generated code and manually fill in all those /* IMPLEMENT ME! */ methods.

Do you think this has value? Would you want to work with a tool that supported that? I am really keen on knowing your opinion.

This is actually old news for many people, but recently I learned (by pure chance) that the OMG issued a RFP for a “Concrete Syntax for a UML Action Language”. Letters of intent are due on December 8th. Submissions, one year after. OMG members only need apply (Aww…). I wonder if anyone in the Eclipse Modeling project is involved in submitting a proposal. Anyone?

Soapbox: since version 1.5, UML has had support for algorithmic behavior specification, commonly called action semantics. It is still hardly used, and most people that consider they know a lot of UML have never noticed it. Some people believe that the lack of an official concrete syntax for action semantics is a barrier to adoption. You see, the OMG defined the semantics and an abstract syntax, but left concrete syntax as an exercise for tool vendors.

As I wrote here before, I don’t really see the value in the OMG godfathering one concrete syntax over all others. Of course, we are talking here about a syntax for human beings, not for tools. Tools certainly don’t need a human-readable concrete syntax, a standard binary or XML format will do. The problem is: we all have our own preferences for what makes a good syntax, and there is no single syntax that will make everybody happy, so we are bound to have multiple concrete syntaxes anyway. We all like interoperability between tools, but when it comes to sugar, we like choice.

But maybe I am wrong. Maybe an OMG-blessed C-like concrete syntax for UML is all that is missing for Executable UML to become mainstream in the software development community. Go figure, we are an amusing bunch. Personally, I don’t care that much. I have been a Java developer for around 12 years now, so I can certainly stand another C-like syntax. We are not talking about a language anyway, it is just a syntax for an existing language, and syntax, a bit like UI, is inherently disposable, if you take it away, the real stuff is still there.

One clear positive outcome of the RFP is that submitters must provide, along with the proposal for a concrete syntax, any changes to fUML* that would be required to support such action language. That will probably help closing some gaps in the UML specification that make it hard to execute if you are stuck with the standard.

There are many other interesting bits in the proposal, but I will leave a more detailed analysis to a future post.

* the Executable UML Foundation Submission says:“Foundational UML Subset (fUML) is that subset of UML required to write ‘programs’ in UML”

I posted this earlier this week on the UML2 newsgroup, thought I would share it here too…

I published a TextUML rendition of the UML 2.1 metamodel that is shipped by Eclipse UML2 here (warning: 5.9k lines, 370Kb of text). It starts like this:

(...)
model uml;

apply Ecore;
apply Standard;

import ecore;

(* A comment is a textual annotation that can be attached to a set of elements. *)
[Standard::Metaclass]
class Comment specializes Element
    (* Specifies a string that is the comment. *)
    [Ecore::EAttribute(isID=false,isTransient=false,isVolatile=false,isUnsettable=true,annotations=[])]
    public attribute body : String;
    (* References the Element(s) being commented. *)
    public attribute annotatedElement : Element[0, *];
end;
(…)

Thought it could be useful to anyone wanting to have a quick look at the UML metamodel. The TextUML renderer does not support all UML element types, so some elements might be missing/incomplete.

I think that is a nice demo of the textual browsing capabilities in the TextUML Toolkit. Of course, much more could be done in that area. If you feel like lending a hand, any help (bug reports included) will be much appreciated.

Shorthand notation for both composite and aggregate associations has just been checked in (r99-r100). It follows the same spirit as the existing shorthand for plain associations (a.k.a. references).

composition <end-name> : <referenced-type-name>;

or

aggregation <end-name> : <referenced-type-name>;

That will result in a new unnamed association with two member ends, one named, owned by the declaring classifier, with composite or shared aggregation type, and another unnamed, owned by the association itself.

Change set explained

When adding a new feature to the notation, the typical change set contains:

• updates to the affected grammar production rules
• implementation of the corresponding model generation handling code
• a few test cases.

In the case of the features presented in this post, the grammar change was quite simple (nicer view):

--- trunk/plugins/com.abstratt.mdd.frontend.textuml.core/textuml.scc	2008/09/16 05:47:13	99
+++ trunk/plugins/com.abstratt.mdd.frontend.textuml.core/textuml.scc	2008/09/16 05:47:20	100
@@ -341,7 +341,9 @@

   attribute_decl = attribute identifier colon type_identifier optional_subsetting semicolon ;

-  reference_decl = reference identifier colon type_identifier optional_subsetting  semicolon ;
+  reference_decl = reference_type identifier colon type_identifier optional_subsetting  semicolon ;
+
+  reference_type = {association} reference | {composition} composition | {aggregation} aggregation ; 

   optional_subsetting = subsets qualified_identifier | {empty} ;

In other words, where one could declare a reference, one can now declare also a composition or an aggregation (gotta love the readability of SableCC grammars…).

The corresponding model generator (a.k.a. compiler) changes were quite trivial as well, even more so if you consider I inadvertently checked in a fix to an unrelated bug around comments (just ignore the changes in lines not in the 300’s).

In terms of lines of code, the bulk of the changes were in the test class for associations, where I added three test cases. I had postponed writing tests for the reference shorthand notation, so I took this opportunity to write a test for it too.

As most test cases in the TextUML Toolkit test suite, the new test cases in AssociationTests have the following layout:

• one or more compilation units with TextUML source code are declared
• source code is compiled and the resulting errors verified (most test cases won’t expect errors)
• the resulting model is checked - were the expected elements created? Do they have the expected features?

Talking about tests

The TextUML Toolkit has a modestly sized test suite (~130 test cases) at this time. It could use dozens, probably hundreds more, but most features are covered to so some extent.

However, as important as coverage, is how much one can learn about the piece of software being tested by reading its test suite. And here is where I believe the TextUML Toolkit’s test suite shines. For example, by reading the test classes, one could (maybe more effectively than by reading the notation guide), learn how the following UML features are exposed by the TextUML notation:

• classes and structural features
  
• packages, imports, profiles
• associations
• multiplicity
• template classes

Trivia: can you find out from the test suite the difference between a private and a public package import? Give it a try and let me know if I am lying… by the way, the notation guide does not cover that yet, although the UML specification, of course, does.

I often see the TextUML Toolkit being compared to tools that produce UML diagrams from textual descriptions. Examples of tools like that are ModSL, MetaUML and UMLGraph. But that doesn’t really make sense, and here is why: these tools produce diagrams from text. The TextUML Toolkit produces models from text. But what is the difference between models and diagrams?

According to Wikipedia:

• A diagram is a 2D geometric symbolic representation of information according to some visualization technique.
• A model is a pattern, plan, representation (especially in miniature), or description designed to show the main object or workings of an object, system, or concept.

Note that even though both terms are defined around the word “representation”, the term “diagram” implies graphical visualization, whereas the term “model” admits any kind of media, basically because models have no concrete form per se.

Now, please, if you are not convinced yet, read aloud 5 times: MODELS ARE NOT DIAGRAMS!

If that didn’t work, well, maybe the facts below will help:

• models, not diagrams, are the subject matter of model-driven development.
• models, not diagrams, can be validated.
• models, not diagrams, can serve as input to code generation.
• models, not diagrams, can be automatically generated from reverse engineering source code.
• models, not diagrams, can be executed.

Even though diagrams are commonly used for representing models, they are not the only way, and non rare not the most appropriate one (yes, I am talking again about the virtues of textual notations, but I won’t repeat myself).

P.S. Maybe it helps adding to the confusion the fact that the TextUML Toolkit has an optional feature that will generate class diagrams automatically from the UML models created with it. However, that is just an optional, loosely integrated feature, and it is definitely not the Toolkit’s thing. Weirdly enough, from my observation, that feature is the main reason most people become interested in the TextUML Toolkit. Well, go figure.

TextUML Toolkit 1.1 is out! This is the first release after the TextUML Toolkit became an open source project. Besides the adoption of the Eclipse Public License, these are the new features that were added in 1.1:

• more UML features exposed by the textual notation: abstract operations and parameter direction modifiers
• more diagram layout controls (compartments, elements across packages)
• support for exporting the class diagram to a PNG or JPG image file (actually, an EclipseGraphviz feature, also available for other graphical content providers)

Also, the TextUML Toolkit is not available any longer as a standalone download. You need to install Eclipse 3.4 first  (3.3 support was dropped) and then install the TextUML Toolkit using the new smart Software Updates mechanism in Ganymede. See new install instructions here.

As usual, feedback is most welcome - blog, issue tracker or forum, whatever option works best.

Since I started working on the TextUML Toolkit more than a year ago, I have been asking myself whether it would make sense to make it available under an open source license.

Open sourcing a product is a tough decision. Once you take that road, there is no way back, at least not without risking a backlash from the community (of course, if you managed to build a community). And even though there are more and more examples of successful businesses built on top of open source offerings, they are still the exception. However, from day one, my plan for the Toolkit has always been to give it away for free. Going from “free-as-in-beer” to “free-as-in-speech” is not nearly as traumatic.

I resisted to the idea while I was working on releasing version 1.0, as I considered it as potentially distracting and of questionable value, as then I knew exactly what I wanted to ship and how to get it done. However, now that 1.0 is out of the way, it seems the right thing to do. The first release provided a good starting point, but the project certainly needs more hands on deck to get to the next level. It is also clear that an open source license means a lot when you are catering to a developer audience.

So, you heard it here first: the next release of the TextUML Toolkit will be licensed under the Eclipse Public License. The source code is already available on SourceForge, and user forums and issue tracking are now also hosted there.

Joining the Eclipse Modeling project (more specifically the MDT subproject) is an option for the future, depending on whether the project succeeds in attracting other contributors.

Using the tool, spreading the word, asking and answering questions on the forum, reporting problems and requesting features are all great ways of helping. Regarding new features, the project needs help on two main fronts: broader coverage of UML (state machines, activities), and better IDE features (such as content assist, templates, symbolic search and refactoring). If you like the textual notation approach, the tool, and feel like you could lend a hand, please do, the TextUML Toolkit needs you!

According to an announcement made on the acceleo-dev mailing list, Acceleo 2.3.0 has been released today. Congrats to the folks at Obeo! The latest bits are already available from Acceleo’s update site, but the download page still shows 2.2.1 as the latest release available.

That is one less excuse for using Eclipse 3.3, which was the latest release supported by Acceleo 2.2.1. An added bonus is that the TextUML Toolkit is much more stable on Eclipse 3.4 due to a nasty concurrency bug fixed in UML2 for the Ganymede release (kudos to Kenn and James!).

I just updated the install instructions for the Pet Store example application. With a new and improved Software Update mechanism (a.k.a. P2), it became much simpler to install the TextUML Toolkit and Acceleo on Eclipse 3.4. For instance, no need to worry about EMF or UML2, they are transparently installed. How cool is that?

(To my fellow 30-dayers: It has been a while since my last post in the 30-day challenge category - at least if you think of how brief it is. But worse, I am also behind the schedule. My goal was to have the first release candidate on the 15th. It is the 17th and I am not quite there yet. Read on for details)

Every now and then, the Eclipse Project goes through quite significant changes (OSGi and RCP in 3.0, P2 now in 3.4). And when the platform moves this fast, everybody living above feels it. New features are not well documented or are not very stable. Tooling for plug-in developers lags behind. Things that used to work before, are now broken.

That is really hard to avoid, even though backward compatibility with the previous release is a hard requirement for the Eclipse Project. I was part of the Eclipse Platform Core team in 3.0 (shipped in 2004) and even though we were having lots of fun with the move to OSGi and the birth of Equinox, it was a lot of work having to implement the new functionality and at the same time make sure all the existing use cases continued to work. And, as usual, some corner cases we missed were only discovered close to the release date, or even right after, when most people will finally migrate from the previous release. Many of the OSGi-aware features were only exposed by the plug-in development tooling in the subsequent releases. And even though we felt like all that backward compatibility effort was draining a lot of our time and energy, users would still get mad at us for introducing regressions, when they didn’t really give a damn about OSGi or RCP.

In hindsight, it is clear that all that work paid off when you look at the impact that OSGi and RCP had in the growth of Eclipse way beyond the realm of IDE frameworks. People are using Eclipse as a platform for embedded and server-side applications, or rich client applications you could swear were native. OSGi itself had a boom in adoption (and features) since when it was adopted in Eclipse and moved from niche technology into the mainstream.

I am sure the same is going to happen with P2, probably in smaller proportions (given its scope). We will be taking its features for granted two years from now, and the pain of change will have been long forgotten. And the good people developing P2 know that. But, this time around I am…

…on the other side of the fence

The plan of shipping TextUML Toolkit 1.0 (scheduled for June 30th) on top of Eclipse 3.4 (scheduled for late June - yes, that should have raised a flag) proved to be quite a challenge. I have had minor problems with the latest Eclipse SDK milestones, which I could work around, but more recently I have faced more serious, blocking issues. And even the non-blocking problems and difficulties, which are just time wasters, grow in importance when you are in a tight schedule.

So I stepped back and decided to and develop and ship the TextUML Toolkit 1.0 on Eclipse 3.3, which was last year’s release. It was not an easy decision, as I will be missing many improvements and fixes (some of them to pretty significant issues) made in the UML2 and EMF components, which are the main requirements. But at least I should be able to move forward in a more predictable pace, and be more confident I have a chance of meeting the June 30th deadline, even if quality might suffer. On the bright side, thanks to backward compatibility, the same update site should still work with 3.4, so users using the Update Manager/P2 in Eclipse 3.4 should be able to install the TextUML Toolkit features, and get better performance and stability.

What makes me feel good is that backward compatibility continues to be one of the Eclipse key values (e4 rumors aside), so regressions receive high priority and are fixed as quickly as possible. The least we (end-users and product providers) can do is to diligently report them.

Contrary to my original intention of working this week on code generation and the sample application, I have been doing some improvements in the graphical visualization of UML models in EclipseGraphviz. EclipseGraphviz (a spin-off of the TextUML Toolkit) is an open source component (EPL) that integrates Graphviz into Eclipse, and among other things, can generate UML class diagrams from Eclipse UML2 models on the fly.

After fixing a couple of bugs, I decided to add a preference page to give some level of control over the way the diagrams are laid out. Here is what it looks like:

You can now turn on or off several adornments such as association end names, multiplicities and membership. For example, this diagram was rendered using the options shown above:

Whereas the following one was rendered for the same model while having only the “Create constraints for association navigability” option checked:

As you can see, enabling constraints based on association navigability can significantly alter the diagram layout. One good reason for enabling that option is to avoid diagrams that grow too much horizontally (as Graphviz will put all nodes of the same rank on the same row), but I personally prefer the former layout.

Side note: I considered dropping the graphical visualization feature altogether for 1.0, as I see it as just a nice to have, and am not totally happy with the quality of the diagrams generated by Graphviz. But every bit of feedback I got for the TextUML Toolkit was that the graphical visualization was really nice, so I changed my mind. But unless serious bugs are found in this area, I have no plans of touching the EclipseGraphviz code again until after I complete the 30-day challenge.

Side note #2: I expanded the FAQ to cover the issue of notation choice and the role of EclipseGraphviz in the TextUML Toolkit.

There was a recent thread about UML on Slashdot, as a reaction to this blog post . The headline: “Is UML Really Dead, Or Only Cataleptic?“. Many posters are clearly bitter towards UML. There seems to be a strong preference for using UML as a communication tool as opposed to as a basis for partial or full code generation (see post on UML modes). Many also complain that the graphical notation is cumbersome and that it hurts productivity (+1!). A few actually like UML; however, it is said that the UML specification is vast and complex and that you should pick the parts of UML that make sense for your case/goals (+1 here too).

Lots of interesting points, but the most negative posts are just misinformed. But that is Slashdot, what should I expect? Java and Eclipse have, in general, a poor receptivity on Slashdot, so I guess UML is in good company.

Of course, while I disagree with those that ditch UML because it was not properly employed in some project they worked, I strongly agree with the complaints about UML (graphical) diagrams being cumbersome and hard to deal with, as I have written here before. But that is not a problem with UML per se, but with the fact most still see it as a graphical language.

UML certainly has its share of problems (design by committee, no reference implementation), but I strongly believe it is very useful and that there isn’t anything out there (I am talking to you, home grown DSLs) that can replace it as the lingua franca for model-driven development.

TextUML is a textual notation for UML. The TextUML Toolkit is an Eclipse-based IDE-like tool for creating UML models using the TextUML notation.

Other tools follow the same approach. Emfatic (now an EMFT subproject) has been doing the same for EMF Ecore for a long time; the TMF project aims to be for textual modeling what GMF is for graphical modeling, and will be based on GMT’s TCS and xText components.

Still, people are often puzzled when I explain what the TextUML Toolkit is. A common question is: “if I am going to write code (sic), why do I need UML anyway?“.

Dean Wampler from Object Mentor wrote on his blog a while ago a post entitled “Why we write code and don’t just draw diagrams“. It is a short post, but he presents very good points on why a graphical notation is usually not suficient and is bound to be less productive than a textual one when it comes to modeling details. For instance, on the saying “a picture is worth a thousand words“, Dean wrote:

“What that phrase really means is that we get the ‘gist’ or the ‘gestalt’ of a situation when we look at a picture, but nothing expresses the intricate details like text, the 1000 words. Since computers are literal-minded and don’t ‘do gist’, they require those details spelled out explicitly.”

Couldn’t have said it better.

I strongly advise you to read the original post in its entirety, but I will leave you with another pearl from Dean’s post (emphasis is mine):

“I came to this realization a few years ago when I worked for a Well Known Company developing UML-based tools for Java developers. The tool’s UI could have been more efficient, but there was no way to beat the speed of typing text.”

Enough said.

Last Thursday happened the 1st Eclipse DemoCamp in Vancouver. It was a very dynamic event, with nine short talks packed into little more than one and a half hours. Attendance was high, I was really amazed to see such a great turnaround. The audience saw a diverse range of interesting Eclipse-based projects being developed in Vancouver/Victoria.

I demoed the TextUML Toolkit and got good feedback and some very interesting questions. The idea of a using a textual notation for creating UML models is still not a very easy sell, and that continues to surprise me. Being a developer, I find working with a textual notation so much more natural than a graphical one that it makes it hard for me to see things from other people’s shoes. I plan to go over the issue of textual versus graphical notations on a future post.

All in all, it was a great event. Many thanks to Tasktop’s Robert Elves and Mik Kersten for organizing it, to the Eclipse Foundation for sponsoring the event, and congrats to all presenters.

In a recent thread on the EMF newsgroup, I came to realize that there are (at least) two EMFs, each belonging to a different class of product, and attending completely distinct requirements.

EMF’s native metamodel, Ecore, is a generic, lean object-oriented metamodel based on a subset of UML.

EMF’s runtime framework provides Java applications with runtime support for object models “including change notification, persistence support with default XMI serialization, and a very efficient reflective API for manipulating EMF objects generically” (source).

I am a happy user of EMF’s Ecore metamodel as a poor man’s UML (EMF team, please take that as a compliment). From Ecore-based models, using a compatible template engine, I can generate all code/artifacts that are prone to automation, be they Java code or not.

The runtime aspect of EMF is certainly useful to many applications, but certainly not to all or maybe even most. That is not to say that the EMF runtime does not provide a lot of value, as it clearly does given its popularity. Nor does it imply that the EMF runtime API has design flaws that prevent its use to be more widespread. The fact is that frameworks, while designed for extension, always impose a certain set of architectural decisions in order to provide value out-of-the-box. Those decisions are bound to make its use more suitable to some scenarios and applications than others. The goal is to make as many people happy as possible. It is clear that the EMF team has pulled off that trick. But that does not mean that using EMF-generated model code is appropriate for every Java application out there.

Model driven development maximizes reuse via a complete separation between problem domain and technological concerns. This separation is critical to allow us to build software in an obsolescence-proof way. EMF’s Ecore provides a good foundation for MDD in this sense, regardless the technology choices for the software being developed. The EMF runtime framework, albeit a valuable tool for a significant range of applications, brings with it a specific set of choices in terms of design and implementation decisions, and as such has a less universal applicability.

However, time and again I read comments in the EMF newsgroup that lead me to believe that this duality might have been accidental, and that the sole reason Ecore was created was to support the generation of Java applications based on the EMF runtime. If that is really the case, this is something that both amuses and worries me. My concern is that if the EMF team does not acknowledge the importance of Ecore as an independently useful product, technical decisions in the evolution of EMF might break the use of Ecore in contexts other than EMF-based Java applications.

Starting today there is support for EclipseGraphviz on non-Windows platforms. Scott Bronson convinced me that while bundling a Graphviz install was a good idea for the Windows audience, on Linux and other platforms that really would not make sense given that Linux runs on many different architectures, not to mention other Unix-like systems where Eclipse and Graphviz are known to work and EclipseGraphviz would not due to lack of a corresponding bundled Graphviz install.

Thanks to Scott’s patches, EclipseGraphviz should now work out of the box on any Windows system or on any other platform where Eclipse and Graphviz were successfully installed. If Graphviz is installed under a location that is not part of the system path, you will have to open the Graphviz preference page, choose the “Specify manually” option and enter the absolute location of the “dot” executable:

Do you create diagrams using Graphviz dot language or would you like to see the UML visualization capabilities on non-Windows platforms? Make sure you have Graphviz installed (Windows users can skip this step), then point the Eclipse update manager to http://eclipsegraphviz.sf.net/update and get the latest build. Any problems, report here or on the EclipseGraphviz issue tracker. Need help? Ask away, either here or on the forum. We only tested on Windows XP and Linux/x86 64 bits so if you are using another platform, please tell us what OS/architecture you are using EclipseGraphviz on and whether it works or not.

A few people have asked for a more convenient way of getting EclipseGraphviz other than by checking it out from the Subversion repository on Sourceforge, so I decided to create an update site with the most current code. Again, this is alpha code, so proceed with caution.

Check out the EclipseGraphviz wiki on instructions for installing EclipseGraphviz from the update site and a few hints on how to use it.

Enjoy. Feedback is most appreciated.

The primary goal of the EclipseGraphviz project is to support Eclipse-based applications that want to use Graphviz as an easy way of producing non-interactive structured diagrams without requiring the complexity of GEF or GMF.

The TextUML Toolkit is the only application currently known to be based on the EclipseGraphviz project. To support rendering UML models generated using the TextUML textual notation, EclipseGraphviz has now the ability of rendering any UML model generated using the Eclipse UML2 API.

In this screenshot, you can see the UML model used in the article “Getting started with UML2” rendered with EclipseGraphviz:

The main benefits are that the EclipseGraphviz graphical rendering of UML2 models is quite lightweight, and Graphviz produces great layouts automatically. The main caveat is that the diagrams are not interactive. Not to mention that EclipseGraphviz is still quite in its early stages, so it lacks maturity and features. And it does not run yet on non-Windows platforms.

There is where you can make a difference. Check out the project from the Subversion repository, give it a try, and contribute with bug reports, feature requests and patches.

In the context of providing class diagram visualization for TextUML Toolkit, I have developed a simple graphical viewing framework for Eclipse. It is content type based, and allows you to view anything a content provider has been registered for. For instance, any image file supported by SWT:

But you can also view the graphical representation of a Graphviz DOT file, and it will even update as you edit the file:

And finally, and also the reason why I had to develop support for DOT visualization in the first place, you can also visualize a UML model (here showing a model created using the TextUML Toolkit):

All these features (except for the TextUML Toolkit itself) are part of the EclipseGraphviz project, which is open source (EPL). No releases yet as this is still very new, but you can grab the source from the Subversion repository. If you would like to contribute to the EclipseGraphviz project, or to the graphical viewing framework, your help will be most welcome.

RC

Just finished a raw implementation of a viewer for GraphViz dot files. Here is a screenshot:

By the way, the project has been provisioned on SourceForge with the suggestive name of EclipseGraphviz.

RC

Even though a textual notation such as TextUML is much more productive when creating UML models, the graphical notation is still better for a high-level overview. So, for the next milestone of the TextUML Toolkit, the main feature planned is a model visualizer using the conventional graphical notation of UML.

The first option considered in implementing that feature was the UML2 Tools project, part of the Eclipse.org Model Development Tools project. UML2 Tools supports viewing and editing most of UML diagram types, and works seamlessly with models created using UML2 and EMF, which the TextUML Toolkit already uses, and that is great. However, it also requires GEF and GMF, what is bad because it significantly increases the download size for the TextUML Tookit (currently at 31MB), already high for the value it currently provides. Also, from some initial experimentation, it seems to be very computation and/or memory intensive. Because of that, it was decided a more lightweight alternative should be found, even more so if you consider interactivity and support for diagrams other than the class diagram are very low on our list.

Enter Graphviz and UMLGraph

Graphviz is an awesome tool for graph visualization. Graphviz takes simple text files (in the dot notation) describing the graph structure and produces great looking diagrams.

However, Graphviz is very generic, and does not know anything about the UML notation. That is when UMLGraph comes into play. UMLGraph produces dot files that generate OMG compliant UML diagrams (like the ones showing here).

So the direction is to adopt Graphviz and UMLGraph into a lightweight, non-interactive graphical viewer for UML class diagrams. We don’t dismiss having a more powerful graphical viewer (and editor) in the future, probably based on the UML2 Tools project, but the focus now is on simplicity.

There are two difficulties into adopting Graphviz and UMLGraph though:

1. Graphviz is a native standalone tool, not a Java API
2. UMLGraph, as a Java doclet, supports only one input representation: Java source with Javadoc comments

Turns out the first obstacle can be easily overcome by wrapping the Graphviz binaries into platform-specific fragments and providing a simple Java API on top of it.

The second obstacle is a bit trickier though. UMLGraph ties the usage of the doclet API into the generation of output in dot form. Breaking that coupling requires a non-trivial refactoring effort. I have been talking to UMLGraph author Diomidis Spinellis and he is keen on the decoupling, and that is the route we are going to take.

Would you like to see what it looks like? Make sure to check out the M2 milestone coming out in mid-June.

RC