Re: [Corelinux-develop] meta class

[Frank V. C. <fr...@co...>]

I believe you have the sense of it.

A general UML of the abstraction is:

Ontology <>----> MetaClass <>----->MetaAttributes <>--|
			^	    		      |
			|			      |
			-------------------------------

So an Onotlogy has MetaClasses
MetaClasses are defined MetaAttributes
MetaAttributes are constrained (restricted) by MetaClasses

So, in psuedo-think :)

MetaClass
	declares TypeOf		MetaClass
	declares Name		String
	declares ClassType	Entity
	declares Description 	String

Going along this line, and instance model could be

MetaTypeRoot
	defines TypeOf 		{0}
	defines Name		"MetaTypeRoot"
	defines	Description	"Root of the ontology"

MetaTypeNumber
	defines  TypeOf		{MetaTypeRoot}
	defines  Name		"MetaTypeNumber"
	defines	 ClassType	Number
	defines	 Description	"Number Type"

MetaTypeInteger
	defines TypeOf		{MetaTypeNumber}
	defines	Name		"MetaTypeInteger"
	defines	ClassType	Integer

etc.

Which would map to:

class Entity;
class Number : public Entity;
class Integer : public Number;

of course at some point in the MetaType hierarchy you determine when to
add attributes which, in effect, specialize it from it's parent(s).

Christophe Prud'homme wrote:
> 
> Hie
> my understanding of the requirements for meta class is that
> it provides :
> 1- traits: static features of a type (traits were originally defined by
> Nathan   Meyers)
> 2- more sophisticated RTTI
> 
> it my codes I have, I think, something like that for point 2
> all objects are clearly defined within a hierarchy of class and each of them
> defines isTypeOf(char*), getClassName() , isA(char*) and the parent,child is
> defined.
> 
> for point 1 traits are a very powerful and simple technique to store static
> features and I use them very often.
> 
> here is a simple example
> 
> template<int Dim, int charSize=8, typename T=double>
> class traits
> {
> public:
>  enum { dimension = Dim };
>  enum { char_size  = charSize };
>  typedef T T_numtype;
> };
> 
> template<typename Traits>
> class A
> {
>  public:
>  enum { dimension = Traits::dimension };
>  enum { char_size = Traits::char_size };
>  typedef typename Traits::T_numtype T_numtype;
> };
> 
> template<int Dim>
> class B: public A<traits<Dim> >
> {
>  public:
>  typedef  A<Traits<Dim> > super;
>  enum { dimension = super::dimension };
>  enum { char_size = super::char_size };
>  typedef typename super::T_numtype T_numtype;
> };
> 
> 
> am I correct in that it is providing 1 and 2 ?
> C.
> 
> --
>  Christophe Prud'homme                |
>  MIT, 77, Mass Ave, Rm 3-243          |  C'est de la buche?
>  Cambridge MA 02139                   |  Non c'est kloug!
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>  http://augustine.mit.edu/~prudhomm   |
>                           Following the hacker spirit
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-- 
Frank V. Castellucci
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