This is the last post in my series of summaries of the Code Generation 2012 conference. After having reviewed the LWC day and days one and two, this third and last day concludes my personal report. Some of you will remember my intense tweeting in such days under the hashtag #cg2012, but I had a good reason: such tweets help me document the event and log the activities, which actually makes the process of writing these summaries possible. So, let’s stop meta-posting and dive into the content of the day D.

Friday 30th, day 3

The last day of the conference started with the keynote “Speed and Innovation through Architecture” by Jan Bosch (@JanBosch). This was very provocative in that it addressed MDSD and Software Architecture within the context of innovation in industrial contexts and presented it from a business perspective: opposite but complementary to the technical content that usually drives a CG session. Jan supported his talk with examples drawn from Nokia, Siemens, and other companies he is either currently working with or worked with prior to his current academic position.

Some of the pearls (argued by the audience in twitter latter) in his talk were:

• The market is moving from products to services
• The need for the speed: R&D departments should have very short innovation cycles. Speed is the primary feature to achieve. (Time to Market)
• Moving faster: no efficiency improvement will outperform cycle time reduction.
• Traditional SW development does not scale. We need to change the way we create SW.
• Amazon releases new software every 11 seconds…
• R&D as an Experiment System
• Decisions should be based on DATA, not opinions
• Learning: the company running the most experiments against the lowest cost per experiment wins
• There are things you can’t predict until you perform tests
• Lean and Agile as Scale: as a dancing elephant (see the photo in the slides)

Some tweets reactions about it:

• @delphinocons: Reducing dev. cycle time is 10x more beneficial than improving dev. efficiency I can see him build the case for MD(S)D from here. #cg2012
• @tvdstorm: No more heavy process. This is going the way of the dinosaurs. @JanBosch #cg2012
• @stevekmcc: @JanBosch 10% more revenue vs. 10% less dev costs (“efficiency”) assumes rest of org has zero incremental cost & demand is infinite #cg2012
• @delphinocons Amazon releases new software every 11 seconds… wow. @JanBosch @ #cg2012
• @pmolinam  ”Learning: the company running the most experiments against the lowest cost per experiment wins” @janbosch #cg2012 #innovation –> Google
• @tvdstorm: @JanBosch’s keynote: crowd sourcing the scientific method at a very high speed. Continuous integration -> deployment -> AB testing. #cg2012
• @pmolinam Arquitecture goals accordingly to @janbosch Simplify, Decoupling, Lean and agile at scale, End to end quality, fight design erosion #cg2012
• @pmolinam “Interconnected teams and organizations asymptotically reduce productivity to zero” -> Twitter? @janbosch #cg2012 #innovation
• @pmolinam Decoupling: NO versions! only the deployed one! @janbosch #cg2012 #innovation <- Hard to achieve out of the web
• @pmolinam Very great keynote! by @janbosch #cg2012 #innovation very inspiring and totally on-topic.
• Great slide @janbosch #cg2012 implication http://t.co/OBiSKfjZ
• @MarkDalgarno: Every engineer at @intuit spends at least 1 day a year with a consumer seeing how their products are used in practice. @janbosch at #cg2012

As commented, this was a great keynote with respect to rethinking the role of MDSD within business organizations and how MDSD is still a great and undiscovered lever to drive innovation inside a company from within the IT and R&D departments. Dear CIOs, take note.

After the keynote, time for a quick coffee and I move quickly to prepare my session on “Multichannel User Interfaces”

In this session, I presented some issues we are working on at Icinetic. When developing a new service or product, UIs are expensive to develop if you have to offer the service in the leading edge mobile platform. The market is fragmented and thus provides several competing platforms and technologies with which to build a UI: XAML/C#, JavaFX/Java, Android, Objective-C/Cocoa, HTML5/Javascript with a JS framework, etc. The technology is changing quite fast and there is an open war to determine who will dominate the mobility space. Developing for any platform’s target UI technologies is neither cheap nor maintainable; is well: they don’t scale. It is in this context where Modeling device independent User Interfaces makes complete sense for business software. I demonstrated one of the prototypes we are building — called Oz UI — which utilizes my work on conceptual user interface patterns and is able to declaratively specify and prototype the UI then generate an implementation based upon any of a set of different widget technologies.

I got a very good feedback from the audience and feel that there is space for creating new tools in this domain that further alleviate the effort required by developers to work within the plumbing present in every development framework.

After the session and with the feeling of work completed, it was time for lunch and relaxation.

My last technical session was: tercnoC xatnyS srettaM (Concrete Syntax Matters) by Steven Kelly. The superbly selected title speaks for itself: when designing a new language there are many considerations to be taken into account in order to make the language pleasant for your users. Usability, concreteness, unambiguity, homogeneity, human perception of colors, forms and text are all relevant when addressing the design of a new language. The success of your language — measured in number of users — will be influenced greatly by these choices. See Steven in action.

Following our last coffee/orange-juice break, we all moved to the closing session: a panel discussion on “Code Generation – how far have we come in 5 years?”, lead by Andrew Watson, who introduced the topic and the panelists: Wim Bast, Steven Kelly, Darius Silingas, and Markus Völter.

Some ideas that were discussed:

• MDSD Commoditization
• Moving from a technical discourse to the necessary business discourse
• The complexity of SW is ever growing; MDSD helps manage the complexity

Some interesting tweets about the panel supporting it:

• @lmontrieux: Final panel session begins at code generation #cg2012 http://t.co/ffQOqyQ6
• @delphinocons: Wim Bast: competing DSLs and LWBs is good for innovation, but bringing MD(S)D to the market requires commodity as well. #cg2012 closingpanel
• @pmolinam @CompSciFact “Before you can design a good DSL, you have to understand the D.” On-topic for #cg2012
• @tvdstorm: Need: live prototyping environments to be able to try out many different designs. Modeling needs immediacy, liveness and directness. #cg2012
• @delphinocons Wim Bast/Darius Silingas: we have to avoid focusing too much on the technical side in favor of the business benefits of MDSD. Agree! #cg2012
• @pmolinam On SoC and abstractions in DSLs #cg2012 Panel
• @stevekmcc We are building the complex systems as ever. DSL helps in this race. #cg2012

Summing up

Finally, I present my personal conclusions on the State of the Art in MDSD based on what I have seen at CG2012:

1. Two main lines of work have arisen in MDSD seen this year:
• Bottom-up using a low-level general language and adding extensions that raise the abstraction level (eg.: mbeddr over C or Webr-DNQ over Java) for a specific purpose (domain), and
• Top-down using a high-level DSL/language with a specific, targeted level of abstraction in order to describe a domain (hiding technology details and other concerns) upon which code generation is applied (samples: Radarc, IFML, MetaEdit+).
2. More effort is needed to explain ROI for potential MDSD consumers (customers).
3. Increasing complexity and diversity (mobile) in technology pushes the market ever closer to MDSD (as there are no other choices).
4. Technology independence (one of the foremost qualities of systems developed via MDSD) provides even greater value when technology is undergoing rapid advances (see the mobile arena for example).
5. Some MDSD technologies are powerful yet also rather complex; more work is required to simplify their presentation in order to increase user adoption.
6. User Interface modeling is gaining momentum this year (with at least four sessions), that being a great and challenging DSL domain.
7. The cloud provides opportunities for applying MDSD; this context already showing adoption in transparent infrastructure (see Mendix for a sample), deployment and configuration (cloud operation).
8. Multi-core CPUs provide opportunities for executing DSL specs with efficient parallel processing.

As always, CG2012 was a great opportunity to take the pulse of the MDSD community, providing a good overview of the current problems and areas of research. If you want to get in the loop don’t miss the next edition — join us in 2013.

I want to thank the work of Robert McCall. He contacted me and volunteered for polishing my sometimes rusty English and making the full text more readable.

After reviewing LWC2012 and CG2012 day 1, let’s continue with day 2.

Day 2, Thursday 29th

The morning started with the first keynote. Markus Völter led the session with the title “Domain-Specific Language Design – A conceptual framework for building good DSLs”.  Here Markus deep down with an ontology approach, reviewing the dimensions of DSL Design: covering nine topics: expressivity, coverage, semantics, separation of concerns, completeness, paradigms, modularity, concrete syntax & process. In the session, he focused mainly on expressivity, semantics, modularity and concrete syntax. I found specially interesting the dissection of types of language extension and composition providing detailed samples in each case. In summary, good and quality stuff as Markus used to deliver. As commented by Markus, this material will be published as a book “DSL Engineering” at the early 2013.

After the coffee break, I entered the Peter Friese’s tutorial on “Traditional and Model-Driven Approaches for Cross-Platform Mobile Development”. Peter demonstrated a very good knowledge of the mobility space presenting nor one or two alternatives but six (6) ways of developing cross-platform mobile applications considering pros and cons. Great talk covering native development (showing iPhone, Android and WP7), HTML5 and JavaScript frameworks like Sencha or jQueryMobile reviewing cross tools like phoneGap. It was a pity that the Wifi connectivity were failing and interrupted in some moments the flow of the demo, but Peter was able to overcome it and show what’s going on.

User Interfaces are always interesting to me so: Achim Demelt session’s was a must see session or me. “Mission: Impossible — Purely declarative User Interface Modeling”.

The session was very good. The slides are not enough, the accompanying demo shown the tool at work. Achim and his team created Silverlight based UIs using a Java back-end. The S4 environment presented is agile enough to model and generate UIs for the ERP domain Achim was targeting.

Next session for me was for the Jetbrains’s guys Maxim Mazin and Evgenii Schepotiev with the talk “Webr-DNQ — web application development with pleasure”.  They show the language extensions Jetbrains has designed over Java using MPS  to build in-house products like YouTrack. This is a very clear sample of the quote: eat your own dog food.

After a coffee, and back to action to a very different session: Steven Kelly lead the hands-on session titled “Have your language built while you wait”. Here some of us creating Language Workbenches where placed in a room with our laptops waiting for customers. During rounds of 25 minutes we were attending them showing the capabilities of each tool and solving a concrete and practical small problem proposed by the customer. 15 master craftsmen, representing 11 top language workbench tools, volunteered their time to build languages for participants’ domains. It was a very interesting format because it not only allows people to try new tools, but also to promote cross polinization between tool makers. From mi side I was there showing Essential and also have the chance to play a little with The Whole Platform with Riccardo Solmi and Enrico Persiani and take a closer look to Ensō with Alex Loh.

Steve prepared a good summary on this session (take a look for the details on each tools). I borrow here the video here .

So far, so good! Another day full of code generation, but the dessert was still missing.

This year CG2012 changed the relaxing punting trip on the river Cam in favor of a conference called “How Apollo we flew to the moon” by David Woods. The result: totally amazing! This guy presented us all a brief but detailed introduction to the Apollo systems and navigation procedures and then deep down on the specific problems on the Apollo XI, the mission where Aldrin, Armstrong and Collins engraved theirs names in the history.

Given the audience, David make special emphasis on the computer devices on board in the Apollo missions. Totally amazing the rudimentary technology used was good enough to fly to the moon and come back! Q&A delivered may geek questions about the Apollo mission that David responded with flying colors to impress even more the audience.

So I couldn’t resist, and bought my copy of his book and got it autographed by David (I was not the only one BTW). A good reading for sure, if you like space and/or engineering.

The arrival to my new job in Sevilla has coincided with the preparations and launch of a new product. We at Icinetic, are releasing Radarc 3.0. Radarc is a very easy to use code generator highly integrated with Visual Studio and targeting .NET technologies.

Radarc has the ability produce multiple architectures using the same base models and keeping in-sync generated artifacts when model element changes. Architectures and DSLs for defining the models are packaged in so called “Formulas”.

Currently, the following formulas are available for download and it is free for non-commercial usage:

• ASP.NET Web Forms + Entity Framework
• ASP.NET MVC 3.0 + Entity Framework
• ASP.NET MVC 3.0 + Entity Framework + Azure Storage & deployment
• Windows Phone 7

Radarc 3.0 is available with three licensing models and its free for non-commercial usage.

Other technologies are available on demand, such as:

• .NET 4.0 Domain Driven Design N-Layered Architecture
• NHibernate & more to come…

Times fly! Code Generation 2012 is only two weeks ahead.

During the latest’s weeks we have been very busy combining day to day work with the preparation of material for the conference.

This year the conference will be held from 28th till 30th of March, in the habitual place: Murray Edwards College, Cambridge, UK.

The programme this year comes with some interesting sessions. I want to highlight some of them:

• The day before, the 27th the Language Workbenches Challenge 2012 takes place in the same scenario. The competing tools will show us how they resolved the current assignment.
• The keynotes by Jan Bosch ”Speed and Innovation through Architecture” and Markus Völter ”Domain-Specific Language Design – A conceptual framework for building good DSLs”.
• David Woods will talk on 29th about “How Apollo flew to the Moon” Don’t miss it!
• The practical session “Have your language built while you wait” driven by Steven Kelly will allow you to solve your problem (domain) in 20 minutes. It will be funny.

From my side, and once established in Seville, I will join the conference with some of my Icinetic colleagues. The activities we will be involved include:

• Attending the full LWC2012 and CG2012.
• This year, Icinetic proudly sponsors CG2012, so we will be present there. If your are interested in MDSD feel free to ask us and we will make you a demo of our work and products.
• Ruben Jimenez and I will be presenting the session “Modelling and Code Generation on the .NET platform at Icinetic” on Wednesday 28th.
• On Thursday 29th I will be taking part in the previously quoted session “Have your language built while you wait” with Essential.
• Finally, on Friday 30th, Ruben and I will lead the session “Multichannel User Interfaces”.

As every year, looking forward to join and meet again with the CG community. See you there, guys!

Plaza de España, Sevilla (By CCSA Tom Raftery)

La comunidad Alt.NET Hispano ha publicado la VAN (desconferencia) sobre Generación de código con Essential que tuvimos el pasado dia 11 de junio. Si estás interesado en MDD, generación de código y como aplicarlo con Essential, este video grabado para la comunidad en español es un buen punto de partida.

Mi agradecimiento a Alt.NET Hispano por el interés en la materia y la invitación a divulgarlo.

Descarga directa del video (562 Mb).

In this long post, I want to share my personal view about these days, and for sure, take note it could be partial and subjective. So, be kind to review also the comments as seen by others like Johan den Haan, Markus Völter, Angelo Hulshout, Marco Bambrilla, or Mariot Chauvin to cite a few and more expected to come. Find the majority of the pointers at the http://modeldrivensoftware.net

In this edition, the conference has been deeply covered via twitter using #cg2011 and #lwc11

As expected, I will be only be able to comment about the sessions I personally have attended. Running three tracks in parallel always force us to choose one and miss two other great sessions.

Day 0. The Language Workbenches Competition

Ten tools were presented in a marathonian session exactly allocating 40 minutes per tool. The Angelo’s egg-timer was implacable: Whenever it rang reaching the agreed time, the speakers suddenly stopped talking unable to end a simple phrase.

The challenge was a competition without a winner or loser, mainly because there was no prize to win (may be next year a generous sponsor could change that). The main objective is to compare how different tools are able to complete a common problem facing modeling, model transformations and code generation to multiple platforms.

Johan den Haan has prepared a detailed report of the tools presented. Take a look on it.

From my side, I have created a feature matrix for comparing the different approaches stressing what I see as different in each tool. It is not complete: some information is missing and some other not yet contrasted so take it as a beta version to be improved.

With respect to my beloved tool Essential, I have to say that I received a very nice feedback from the audience. See a sample of the twitted comments:

kthoms: @pmolinam Has a high voltage notebook – projector crashed on plugging in. Now let’s see how he could improvise the situation #lwc11

stevekmcc:  @pmolinam Showing #Essential: major theme is separation of concerns, so opposite to Rascal #lwc11

stevekmcc: #Essential looks very clean compared to other text or text-projection workbenches #lwc11

delphinocons: RT @stevekmcc: #Essential looks very clean compared to other text or text-projection workbenches #lwc11 <== I agree. Relaxing to the eyes.

delphinocons: #lwc11 The Essential metamodel is smaller than EMFs, and a little larger than MetaEdit+’s

meinte37: @pmolinam is the first to finish before the egg timer at #lwc11. That’s because he cuts down to the Essential-s

JohanDenHaan: @pmolinam nice presentation and demo, good mix of slides and demo. Great timing!

Day 1. Code Generation 2011 starts

I started the day giving an initial talk about Introduction to Model Driven Software Development.

Later on, Obeo guys (Mariot Chauvin & Stéphane Begaudeau) presented how to use Obeo Designer to create sensible graphical DSL tools on the top of the Eclipse framework. Obeo uses model interpretation over the EMF models to create in runtime GMF based editors.

Panel: Build or Buy – who should develop and own your DSLs and generators?

We played a nice game with the following roles:

• Juha-Pekka Tolvanen (MetaCase), the moderator
• Jos Warmer (Independent) , the homegrow tool maker
• Pedro J. Molina (Capgemini) , the consultant
• Johan den Haan (Mendix), the tool vendor

More soon than later, Andrew Watson and Markus Völter join with the rest of the audience in the discussion. Of course, there is not an easy answer to that question and depends a lot of the particular context and requiring thinking about, but not only on:

• the experience of the in-house developers with MDD
• the level of criticality of the process for the business to be automated (core or non -core to business)
• the existence of tools able to provide the requested features
• the need to split the business process from the current technology

Type Systems for DSLs.

Markus Völter presented a nice library he has been creating to help with the type checking in expressions of DSLs. After a gentle introduction to type checking, he introduced three different approaches to the problem:

• recursive type-checkers,
• union based (a la MPS) and
• table driven (a declarative way of the first one).

Day 2. Getting speed

Terrence Parr Keynote was one of the more awaited talks in the conference. Many of us use their tools on a daily basis like ANTLR and StringTemplate. So having him here is quite special. In his keynote titled “Why program by hand in five days what you can spend five years of your life automating?” he let us some pearls like the following ones highly twitteable:

• “XML is not for humans beings, just for machines.” (Donald Knuth, the father of TeX support this, and I am not going the one to contradict this)
• “Programmers are lazy.” Yes, we are. We don’t like repetition of tasks, trivial or not, because we get bored, so we always try to automate things. And this is our main driver and source of fun.
• “Automate the things more prone to human errors”. Automate the tedious work!
• Running a test does not increase the quality of the code.

MetaEdit+ Hands On

MetaCase MetaEdit+ was of my pending tools to try from previous editions of CG. I had the tool, I had the chances but not the inline tutor to allow me to get advantage of the tool. Risto, Steven and Juha-Pekka did a great work in the “hands on” session been able to not to left away any of the practitioners. They have did this lots of time and they are good teaching it.

Definitely, the learning curve of MetaEdit is not big, but for sure, you need the initial proper training to get the grasp of the tool to start creating your own graphical DSLs. Been a tool implemented in Smalltalk and using a repository, MetaEdit provided an edition experience quite different to the ones more used to edit traditional files.

Generating Graphical DSLs

Marko Boger, one of the fathers of the Poseidon tool, presented his work about applying DSLs to describe graphical DSLs. The idea was well received, and later on in the local pub called The Castle Inn an informal Birds of a Feather session was settled to create the Spray project to join forces and create a common core DSLs to help in generating graphical DSLs.

Modeling the UI

To end the day I gave a talk about how we take in account to model the User Interface of a business application. The topic is important because the IU is not always pondered as it should be. The UI is the only aspect the user will see from any system we build. Approaches to modeling and code generation based in a pattern based approach were presented with the help of briefs live demos using Essential and Io tools.

Day 3. Closing a great edition

Ed Merks Keynote

Ed is the leader of the Eclipse Modeling Framework based in Montreal and now working also for Itemis. In his keynote he remarked some of the prejudices people use to have against code generation and (UML) modeling, leaving also some great quotes:

• “Resistance is futile: Best practices will be assimilated by code generators.”
• “XMI sucks because XML sucks. XMI sucks for transitivity.”

Ed talks reinforces my idea that, talking about software, Europeans are usually more instructed in the university in formal methods and theories where Americans uses to be quite more practical and take a more empirical approach to software engineering or computer science.

It is interesting to see that mostly all the participants in the LWC with the exception of Intentional are Europeans. Well, Charles Simony (the owner) and Mats Helander (the presenter) both from Intentional are also Europeans. So, there is no interest in Language Workbenches in other continents apart from Europe?

Goldfish Bowl: “Code Generation as a normal programming practice”

Jos Warmer lead this session were all the interested participants shared thoughts about how to integrate code generation with traditional styles of development.

How to create a good template: Go to your best developers and tell them: “write this DAO code file as it were the last time in your life you are going to write it”. Then abstract it and you got it. If the further in time found a bug, they can always came back and fix the template also.

Final panel: “Models, DSLs, Transformations: The Next 5 years”

In the closing plenary session, future directions and incoming challenges were addresses by the panelist and the audience.

• Andrew Watson focused on resolving business problems instead of technological problems.
• Jos Warmer encourages us to build better tools and better languages.
• Johan den Haan pinpointed some incoming trends: Mobile, cloud, social, multi-core and poliglot languages.
• Wim Bast commented about the need for parallelization and the best way to achieve it is to move to a more declarative DSLs allowing us to exploit the intrinsic parallelization in the execution of such algorithms. Wim pointed out also about the difficulty of making prediction about the future.

So, I put my two cents remembering the genial quote of Alan Kay: “The best way to predict the future is to invent it”.

My position is that we have the tools, we have the knowledge… so, we should put all our efforts in improving the tools. Good tools will make MDD mainstream soon or later. So, I want to see it happening: let’s improve our tools now better sooner than later.

Conclusions

The LWC has been a great idea made real. Having the opportunity to compare solutions and styles of tools has been quite productive for all of us. All the participants were happy with the idea of repeating next year and the next edition is looking for the next challenge.

Twitter this years has expanded the real-time conference far away that the walls of the College. Colleagues like Rui Curado, Xavier Seignard, Jordi Cabot, Angel J. Lopez or the AltNet Hispano group to cite a few I am aware were tracking the conference and taking part via twitter. This enriches the experience and makes it more participative.

Some tools, highly integrated with the Eclipse environment were suffering during the conference live demo failures. This is not an exception, but a warning signal that some task that should be easy are getting complex and complex when the number of dependencies to run a simple task is out of control. The friction level of these environments is definitely something to keep as low as possible. Model interpretation versus traditional code generation can be helpful also to reduce startup times and opening another instance of the same environment.

The new born project Spray (as reported by Karsten) can be quite helpful as a neutral DSL definition for describing graphical DSL in an technological agnostic way. The risk however is if it is too close to a certain technology stack like GMF or Graphiti it will only be used in such context. To my understanding, a Spray definition should be implementable also in Microsoft DSL Tools  to put a extreme counterpart.

If a contest for the novel tool of the year will have ever existed in CG, IMHO this year had been awarded to The Whole Plaftorm by Riccardo Solmi and Enrico Persiani. They have a nice and cool looking projectional tool that was deeply unknown to all of us. So, welcomed to the club!

XML is definitely not for humans (Terrence Parr) and XMI sucks for XML transitivity (Ed Merks).

Finally Mark Dalgarno and his team were superb organizing all the logistics to make all of this possible. Thanks to everyone and see you there next year.

The Code Generation 2011 conference and the Language Workbenches Competition 2011 Workshop are quite close in the calendar.

I want to celebrate it with the MDD community sharing my work on Essential (a tool designed for acquiring speed with Model Driven Development). On 11th may 2011, version 0.4.44 has been released as the first public beta.

Essential is a meta-modeling and code generation tool providing specific DSLs to define and consume:

• Metamodels
• Models
• Templates (using StringTemplate) &
• Transformations (Model2Text and Model2Model)

Try it also with the sample projects created for the LWC 2011 challenge.

Finally, I will also be there presenting Essential as a solution to the challenge. It’s a nice excuse to go there, just in case!

Now I can hear in the background the sound of knives being sharpened, nevertheless with an Olympic spirit. }:)

If you want to see the State of the Art of the next generation Software Engineering tools in action, don’t miss the opportunity and join us. See you there!

When building a new tool for modelling and code generation like Essential, one has to rethink again what template engine use to drive all the machinery. In code generation contexts, template engines are a good field for innovation and your choice will be with you probably for the full lifetime of your tool.

In this post, I will try to introduce and explain why StringTemplate is a superb engine for doing code generation and why you should consider it if dealing with a code generation scenario.

As commented before in other post, I felt in love with StringTemplate in 2005 when I discovered ANTLR and StringTemplate during the development of a MDD workbench for a customer. Prior to that date, I had tested many template engines and also developed on my own a pair of them. For one reason or another, I was not comfortable with the language, the coupling of the template with the transformation control, or the maintainability of the templates in the long term. As the time goes by, this last point arises as crucial to maintain and evolve your architecture.

Therefore, one could say that I am being quite loyal to StringTemplate for the last 5 years, and that too much for technology, moreover, for a product software. And such loyalty is definitely not my merit for not been promiscuous in this issue, but a merit of StringTemplate: I’m still looking for new ways for improvement and didn’t find one better to my needs. (Note: this is probably the best compliment I never paid to a piece of good software.)

Some products shine thanks to the many features they provides, StringTemplate sparkles for avoiding adding features in the wrong place. I will elaborate a bit more on that.

MVC

Model View Controller is an old and good “classic” architectural pattern providing a solution to organize the pieces of a user interface. Originally proposed by Trygve Reenskaug, in Smalltalk in 1979. It has been lately again on fashion, especially in the building of web sites, multi-channel user interfaces and promoting UI testability thanks to the application of the principle of Separation of Concerns that the pattern provides.

There are many variants or dialects to MVC out there, but the simple one is enough to describe our scenario: code generation.

Code generation can be seen as a classic MVC domain with the three roles easily identifiable:

• A model: the variable data in consideration, the metadata to be generated in this case.
• A view: the template with the form of the target language and providing holes or slots to be later being fill in (the output).
• And the transformation controller: the piece in charge of selecting with model parts should be selected, combine and finally inserted in which template holes/slots to render the final and concrete view.

The main problem with traditional template engines is that there are lots of template engines that mix the last two roles (for example all coming from web development in the flavour of JSP or  ASP variants). The view and the transformation controller are intermingled and this situation, in the long time, is not good. I found this strict separation of responsibilities crucial for the maintainability of the templates.

And StringTemplate does exactly that. It syntax and features, although could be strange for the first time, was carefully selected to not allow you to do control choices in the view. It allows to define templates, declare named holes (or slots) and an inline for-each and if statements.

Let’s review a basic sample of StringTemplate syntax:

group mail;

genMail(msg)::=<<
Mail: Subject $msg.Subject$
From: $msg.From:genAddress()$
To: $msg.To:genAddress(); separator=”, “$
>>

genAddress()::=<<$it.Name$ ($it.Email$)>>

The sample contains two templates: one for a mail, and a second one for each address. Templates can have parameters explicit parameters like name, but also there is an implicit keyword (it) to reference the current iterating context.

Named holes or slots are defined are marked with $expression$ where expression is a constrained expression resolution of the model properties received.

In the sample, genAddress() template will be invoked to resolve the From and To properties. Assuming that From is a monovaluated property and that To is a list, the template iterates throw the collection received and evaluates the template for each item. Note the separator modifier used to describe how items should be rendered.

That’s all in the template, the view. It’s forbidden to compute any value inside the template. The idea is that only read operations are going to be done into the model to get the data needed to fill the template.

How to consume the template?

From the transformation side (the controller) consuming a template is something such straightforward as the following one:

//1. Select the template
StringTemplate tlp = group.InstanceOf(“genMail”);
//2. Set parameters
tlp.setAttribute(“msg”, message);
//3. Get the result
string result = tlp.ToString();

It is frequent to find people complaining StringTemplate about not having enough freedom for example to call functions from the inside. But this is not a missing feature, this done on purpose to assure no side effects of such computations. The motto is; if you need to compute something, do it the transformation stage.

This only has covered a very basic intro to StringTemplate. If you are interested you can browse for more contents in the main documentation of StringTemplate.

Of course, Essential uses StringTemplate!

ST & ANTRL on Code Generation 2011

By the way, the father of StringTemplate and the superb meta-compiler tool called ANTLR is Terrence Parr. He teaches compiler construction in the University of San Francisco.

I was planning to prepare this post for some months, but in the meanwhile, Mark Dalgarno (the main organizer of Code Generation Conferences) has surprises us announcing the next keynote for CG2011.

I am quite happy to see that, as announced by Mark, that in the next edition of Code Generation 2011 Terrence is going to be present as one of the invited keynotes!

So, if you are interested in all of these topics, join us and meet Terrence on May 25-27, 2011 in Cambridge, UK on Code Generation 2011.

The call for speakers for CG2011 is open till January 15^th 2011.

To know more:

1. Enforcing Strict Model-View Separation in Template Engines, Terrence Parr
2. StringTemplate
3. ANTLR