"no fluff just stuff": day one, the keynote

Posted by anton
on Tuesday, May 23, 2006

the keynote is what finally delivered that "blow your mind" experience that i was looking for. it started rather innocently with the usual run-of-the-mill DSL talk - traditional coffee-ordering DSL, etc. however, a little bit into it, and there was a nice distinction made between internal DSLs and external DSLs - something I have not articulated as clearly to myself.

internal ones are built on top of the language they are written in; they have full access to the underlying language, but they are also bound by its syntax and features. external DSLs is something you write a parser for, and then either interpret or compile them. external DSLs can do anything, at the expense of writing and maintaining a grammar (strangely enough, JavaCC is not used as an example, although yacc and lex are (no bison though!)), and lack of IDE support (auto-completion, color-coding, etc). a very simple way of distinguishing the two, very nice.

next is a statement that OO is not a panacea - not everything can be neatly modelled in hierarchies; not everything is an object. instead a lot of problems are best modelled in a language. here i digress and refer to another very pertinent rant by steve yegge: "execution in the kingdom of nouns." this is a very welcome approach, especially going back to functional languages and DSLs. context is everything; the same functional language can result in different representations, depending on the context (an example with ruby DSL and several different includes at the top that change its behavior).

next is something i have not thought about until now - the fact that none of the IDEs these days work with text - it is all abstract syntax tree (AST) that we work with. this is what allows IDEs to perform refactorings and all kinds of other tricks. this is why IDEs used to require one to compile the code before it could be refactored, but now they are getting better and better at handling broken code (i.e. code where some of the branches are missing). also, do not forget the predecessor of all small languages - Unix shell. it would be interesting to see where it failed, and where microsoft monad is failing.

finally, he whipped out JetBrains MPS - a tool for metaprogramming developed by the creators of IntelliJ. it brings the power of IDE to external DSLs - code completion, color-coding, syntax verification. in other words, one can design their own DSLs, and have an IDE that supports it. the tools looks very promising, although somewhat lacking "productionalization" side. seems like the team is waiting to see what the big boys (microsoft with software factories, and with intentional software) will do, and then offer an product to support it.

this leads nicely to the stuff i have been struggling with lately at work. i do not believe in MDA tools - any generated code is the code one has to maintain, and abstractions there leak very easily, especially when it comes to distributed enterprise code. so the approach to raising the abstraction level and getting closer to the problem domain is to use terse, expressive languages. these languages could be internal or external DSLs, as neal showed in his presentation. alternatively, the same domain (as long as the underlying core representation of the domain is the same AST) could be represented with graphical tools. and this is the stuff that i do at work on a current project - a well-defined space of enterprise integration is modeled using simple GUI tools that include all the building blocks - queues, web services, mappings, flow control, database connectivity, adapters to other apps. i was uneasy at first, feeling uncomfortably close to the MDA world, but now I can view this as yet another form of DSL.

and this leads to another topic i have been pimping left and right: given these simple integration tools and packaged products, a typical enterprise (the one that can be fit into the business model offered by these packaged products and can afford them) will require a very different type of "architect" and "developer". since it takes only a couple of hours to knock out an integration scenario, mapping a message from one system to another, complete with HA/failover/load-balancing/security/etc, then majority of the work would require less and less in-depth technical skills, but more and more of a business knowledge. these people will know a lot more about the business, and a lot less about computer science. granted, the breadth of knowledge is still essential to avoid blunders, and they would be technical people first of all, but a lot of their expertise will shift to the business domain, once the infrastructure and packages are in place. my favorite tabloid happens to reaffirm these sentiments in a recent article: "SOA predicates rise of the enterprise architect".

this kind of architecture still requires a lot of technical knowledge and developer's background, so the promise of "situated software" is still just a dream. it does, however, highlight the difference between the developer and the architect, as well as the different between application architect and integration architect (especially the one that depends on business domain knowledge). my problem is that i still enjoy developing things so much - i like building them, i like seeing them being used by people, i like tweaking them as they run. i like doing hands-on stuff, this is why i still do things on the side; but i also like the challenge of developing large systems that do require a significant domain knowledge. the question is whether my current occupation is indeed a domain that i am interested in knowing more about.

in retrospect, i think a lot of the talk came from martin fowler's article on language workbenches, which follows the same general layout as neal's talk (neal also quotes fowler quite a lot, but then who doesn't? the man deserves it; i just wish i had a better memory). in any case, the talk was excellent, and i am looking forward to digging more into this topic.

the whole keynote is available on neal's site: slides, samples

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