Re: Ada and UML

[nobody <nobody@nowhere.com>]

Yannick Duchêne (Hibou57) wrote:
> Le Tue, 31 Aug 2010 23:20:41 +0200, nobody <nobody@nowhere.com> a écrit:
> 
> I do not really believe in automatic source generation from UML
Neither do I because
- UML is too large, writing a model translator to cover it would take 
longer than writing the system you want to generate.
- UML makes it possible to create models with internal conflicts.

> Or else, may be these systems use 
> something  to tell “for This, use That”. 

As Simon Wright commented. The thing we use is Executeable UML (xtUML). 
I use bridgepoint. For C++ generation we use a model compiler from 
Mentor for Ada we have built one from scratch.

Regarding the for this use that, use it happens. Often. But not always. 
The model compiler is in many cases quite as capable as I to analyze the 
model and decide if instances of one class should be allocated 
dynamically or created once and for all in an array. If traditional 
pointers or some other mechanism should be used for relations and so on.

> Just think that in Ada, you may 
> have for  example at least, where polymorphism is required, two ways to 
> do (when  feasible, sometime only one will applies) : static (via 
> generics) and  dynamic (via tagged or interface) polymorphism. How can a 
> system know it  should use this or that ? This requires a human
> analysis, to say “well,  this can be statically known, so let's use 
> static polymorphism” or else  the opposite (just an example).

There are of cource such examples. But remember that when doing the 
translation from model into code you have the whole model of your system 
available in a databas and can can look at things from a much better 
perspective than when you are coding a single file.

An easy to understand example is relations. If you draw a simple line in 
the class model you state that there is a relation. But the model 
compiler can look at every single line of code in your system to see if 
you use it (navigate) or not. If it sees that you never use it, it wont 
have to generate the code to maintain it and if it finds you only 
navigate one direction it can add the code neded for it to be one way 
only. (Now many hard core coders will feel lost, what does he mean one 
way only, arn't they all? No in xtUML they are always bidirectional, 
composite, aggregate and navigability as in UML does not exist).

> Your point makes me think about the so called “Executable UML”.  
> Unfortunately, I do not know anything about it. I am just pretty sure 
> this  cannot be automated.

I think it can. We are in the process of completing a pretty large 
system. Its got ~650 classes of which probably around 200 has state 
machines. Generated system is > 3000 ada packages.

> If you wan to tell more... just do :)
Sorry, not allowed to give details. Call Mentor, ask for when John Wolfe 
or Cortland Starret can be in your area, you want to have a look at 
their system modelling products.

Simon mentioned distribution. We use that. In our system we can mark 
classes and services as distributed. Then the model compiler generates 
definition files for the broker and in the classes it generates all the 
interface code needed to distribute things when it is updated.

So, do I have anything to complain about? Yes
- Price of the tool.
- Your first project will fail. Try to combine this knowledge with the 
pricecs when you seek finansing.
- Availability of model compilers
- Constantly having to defend the method
- Performance of the model compiler. Coming from a world where a 
recompile takes perhaps as long as 15 seconds entering a world where 
regeneration/recompilation takes three hours is sometimes (read always) 
hard. The generated code is probably faster than anything I could have 
written myself.

Regarding SPARK I know just about nothing. I know there has been work on 
  modifying the Ada compiler to produce spark code. Do not know how far 
that has gone or what efforts need to be done.

There has also been work on generating VHDL. Just think about it. Model 
a system and end up with hardware specific for your problem.

One strange thing the non believers tend to bring up is that software 
development needs to be fun. My comment is that I have now done this for 
six years. It has been the most interesting years of my twenty as a 
professional software developer. The productivity you can reach is 
beyond anything I had imagined before.