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Re: [m2t-dev] RE: [modeling-pmc] Xpand/Xtend and MTL/QVTO 


Artem,
The point I was trying to make was you don't need "yet another language" to try new things, as you'll duplicate what's already done anyway (e.g. all base expression stuff, QVTO ModelTypes, etc).
So why do people invent new programming languages when there's let's say 'Java'? Won't they just duplicate all base expressions and many other concepts? It's not possible to remove or change concepts from standards without loosing compatibility. Unfortunately this is necessary in order to evolve. 




*Constraints + helper methods*
Why should I write all helper methods in a separate file,
when such a method is only used in one or two constraint in
the same file?


What's the problem with few OCL's context, def and inv in the same
file? (def: for helpers, inv: for constraints)?


It's that there are defs in OCL and queries in QVT.
How do they differ?
Original question was about constraints and helper methods in the same file. To me, single OCL file with constraints (inf) and helpers (def) is possible and hence, solve the issue - nothing to invent here.
Again: Why do people invent frameworks like GMF? Isn't it possible to build graphical editors without it? problem solved - nothing to invent. 






*Model transformation with concrete syntax method bodies*


Just curious, how you gonna handle FILE statement withing these
templates?


I don't need a FILE statement therein, because such strings go into
the model being transformed not in a file.
Or do you mean conceptually from a language designer view point?
I mean, how would you forbid clients from using FILE statement from their templates you intend to invoke from a transformation? 

How about a compiler check?




*Code generation uses intermediate model transformations*
When generating code I use helper methods to derive values
from the input model, things like


It's already in QVT, no need to invent a thing ;)


What is in QVT? Code generation capabilities?
I want to be able to define templates and model
transformations in the
same file.
The usecase you described was intermediate model (JavaClass), that's the thing already done in QVT. Given one can invoke QVT operations from Xpand - consider problem solved. Not from a single file, though, but as you mentioned, it's "spaghetti" code, and rarely percieved as good code. 

It's not spaghetti code generally! That's what I was trying to say.
Again, the point I'm trying to make is that one don't need to have all the basic stuff done himeself just to research on new approaches. I'm arguing statement you made: 
need something which drives standardization
(like EMF does for EMOF).
A standard can only evolve if we have made some
experiences with new things. So how should we
do this if we're all stuck to standards?
First, it turns out a lot of things are already possible with "standards", just need to get using them, rather than ignoring them.
I don't ignore them, would I otherwise be aware of their limitations? (I'm also aware of some good things in it, but it seems that I don't have to elaborate on this here ;-))
Second, nothing prevents you from imporving a standard, trying new things on top of it. 

The specification prevents me from doing so.
One really good thing about standards is that different implementations are compatible with each other. It's really hard to stay compatible and improving a language at the same time.
All in all it sounds like you're not really interested in going beyond the OMG standards, and that's perfectly ok. But than I really wonder why you don't use and contribute to MTL, as it's OMG's answer to M2T. 

atb,
Sven

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