[sc34wg3] New TMCL slides

Lars Marius Garshol larsga at garshol.priv.no
Fri Nov 6 13:37:29 EST 2009

* Dmitry
> Is it possible to add an item for discussion: support for multiple  
> association signatures.

Sure. It's registered as an issue now:

I've also added it to the end of the TMCL slides.

> It seems that current draft promotes definitions like works_for 
> (Employee,Employer) and has less support
> for associations like works_for(Person,Company),  works_for 
> (Person,Non-profit_Organization)

That's true. However, this is deliberate: we don't want to encourage  
this style of modelling. We believe that if there is a semantic  
difference between the two signatures it's better to create two  
separate association types.

Having said that, it is possible to specify an association type like  
this, if somewhat weakly:

works-for isa tmcl:association-type;
   has-role(person, 1, 1);
   has-role(company, 0, 1);
   has-role(non-profit-organization, 0, 1).

Of course, this allows unary and ternary associations as well, so it's  
less than ideal.

--Lars M.

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