16 Apr
2013
16 Apr
'13
4:15 p.m.
Hi,
So about traits, we agreed with Doru that we probably are all talking
about the same thing with different names.
I want multiple inheritance in Fame in the sense that I want to be able
to say that a JavaMethod is an Entity + a BehaviouredEntity +
TypedEntity + a ContainerEntity
Conflicts needs to be resolved ans traits are the best solution, we
agree, but I am reluctant to call it trait because it seems like a
strong reference to Pharo's traits.
Anyway, let's call it traits as long as we agree that they don't suffer
from Pharo traits limitations
FameTraits should be "statefull traits" (unlike PharoTraits) because
Famix primarily defines structure.
I don't like Alain's proposal (sorry Alain) because it introduces a new
concept in the metametamodel where I don't think it is needed.
About Fame (or any metametamodel) Damien talks about boxes and links,
and it seems an appropriate level of abstraction. I don't like the idea
of having to say Fame has blue boxes with "normal inheritance" and green
boxes with "trait inheritance".
The immediate solution could be:
- Fame has only one kind of boxes and all inheritance allows for
aliasing and restriction of the inherited properties ("traits
inheritance" therefore)
The problem is how does this map to a Pharo implementation?
Because Pharo Traits are stateless and Pharo classes don't have "trait
inheritance"
I don't know right now especially if we insist on having 1-to-1 mapping
between a Pharo class and a Famix box.
But let's try not to limit our solution to what we can implement (as
much as we can)
The idea of having code generation was exactly to avoid this problem.
Even if I don't know how to do it nicely for now.
As for another question of steph: why would we represent things like the
type of a variable as an association, it is because it would allow to
build mooseChef queries directly on this.
nicolas
On 04/15/2013 11:09 PM, stephane ducasse wrote:
On Apr 15, 2013, at 11:12 AM, Anne Etien
<anne.etien(a)univ-lille1.fr> wrote:
--
Nicolas Anquetil -- RMod research team (Inria)
Hi,
Sorry for arriving after the battle.
I just want to talk about my experiment in metamodel and model generation.
It is clear for me that the concept of Trait should not appear in Fame. It can be use in
its implementation, but can't be considered at the same level than Element, Class,
Property or Package.
Why?
I fully agree with Nicolas, when he says that
Doru is talking programming and he is talking metamodelling.
I do not see why this
is an important difference.
So Fame is a metametamodel. What is the concept
that we want to implement with Traits (or something else) that does not exist currently in
Fame? This concept is reuse. A class can reuse several properties from another or several
other classes. Sometimes, we want to specify that the property is not reuse as such but
using alias...
There exist different way to implement this thing. Smalltalk calls it Traits, Eiffel
calls it inheritance (there exist perhaps other). There are certainly some differences
that are yet too subtle for me.
Moreover, methods do not appear in Fame so according to me Traits should neither not
appear. But it may happen that I do not understand how it should be introduced.
Considering the generation. It is currently performed a lot. It makes sense only if we
don't touch the intermediary nor the final level, otherwise the high level and the low
level are no more align.
I hope it can help in the discussion.
Anne
Le 13 avr. 2013 à 09:08, stephane ducasse a écrit :
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https://www.iam.unibe.ch/mailman/listinfo/moose-dev On Apr 12, 2013, at 1:32 PM, Nicolas Anquetil
<Nicolas.Anquetil(a)inria.fr> wrote:
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https://www.iam.unibe.ch/mailman/listinfo/moose-dev On 04/11/2013 09:04 AM, stephane ducasse wrote:
> Nicolas
>
> I would really like if you could (with camille/anne/damien/usman) have a document
(can a couple of slide)
> where you precisely shows the problem synectiquers encountered with FAMIX.
> It will help for the solution/paper :)
> And it will help me to understand what are the key problems.
>
> Stef
Some problems we see with current Famix.
Several of them just say that entities have too many properties that do not make sense
for them.
give example
Other could be solved by adding more properties
to generic entities.
but usless for others :).
This is what prompted us to think about multiple
inheritance (or traits :-) ) to compose new entities from a set of simple
"properties" (not in Famix sense of property).
traits-based :)
indeed traits should be good for that.
Probably what you want is to have pair of traits that you apply to both end of a
relation also.
- Invocation is designed for OO. There is no
receiver in procedural languages. This is a semantical problem, but practical too as
'printOn:' has to be redefined to show 'from -> to' instead of
'from -> receiver'
but we could have a superclass for call and a
subclass for invocation?
- Invocation is designed for "non-typed
language". In statically typed languages or procedural languages one knows (or has a
pretty good idea) the function/method called. In these cases, 'candidates' adds
unnecessary complexity
Really? In Java there are cases where you do not know. For
example if you have an interface: you may have different classes?
- Some relations between entities are reified
(Associations) other not. E.g. Access is an association, but the type of a variable is a
"simple" relation.
this is the question of what is your domain and if
you have to attach information to the relation.
To me I do not see why I would like a relation for type.
BelongsTo is not reified,
Why do you want
to have pointers as relations?
To me it will blow up metamodels for not. I do not see the value of having a method
belongs to a class as a relation.
neither is AnnotationInstances, …
there
it could make sense.
- Abstract Famix classes like NamedEntity inlude
many properties that are Java specific (isAbstract, isFinal, isPublic, ...), so that a
Function, a Package or a LocalVariable have the isAbstract, isFinal properties and
AnnotationInstances relation.
Yes the tyranny of the dominant decomposition but
now do you want to have to express everywhere where
- This is further complicated by the fact that
these properties are derived from 'modifiers'. So when looking at the
meta-description of NamedEntites, one sees many redundant properties.
yes probably
should be rethought
- A language like Cobol has no functions, it has
paragraph that is a sequence of statement with a label to go to it and a return statement
(with no value) at the end. For them 'signature' and 'parameters' are
meaningless.
so you will have a hard job to always compose a new model for each language if you do
not accept some interpretation.
It also means that you will have hard time to reuse tools.
- 'functions' are defined for
ScopingEntity which is not a BehaviouralEntity. But there are cases where we want both (a
Pascal program would be an example)
this is a nice one :)
- all sourcedEntities have a sourceAnchor and
comments, which does not make sense for ScopingEntities, or ImplicitVariables
- for synectique we want an alternative notion of container where a container only
contains BehaviouralEntity, not other entities (a Smalltalk method would not be a
container).
so it would be interesting to start identifying the traits you want to
have a build a libraries.
nicolas
--
Nicolas Anquetil -- RMod research team (Inria)
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