Re: TMQL: Direct (super|sub)types?

Rani,

I am agree that the TMDM says supertype/subtype is transitive.

Why do you read that to mandate a default in a query language?

That is I agree that the relationship is transitive, but the operators 
in a query language should offer users capabilities they need.

LMG has already observed that users have some need for a non-transitive 
operator for superclass/subclass.

The presence of a non-transitive operator has no impact on the existence 
of transitivity, it simply doesn't take advantage of it.

Hope you are having a great day!

Patrick

On 03/03/2011 06:48 AM, Rani Pinchuk wrote:
> Dear all,
>
> On 03-Mar-2011 11:59, Patrick Durusau wrote:
> > Since LMG mentioned that it was found useful to have a special
> > construct for the "direct" case, my suggestion was that we make
> > that the default and yet at the same time provide an operator
> > for the second case.
>
> I think that what Lars meant is that a special construct for the 
> "direct" case is useful. That's all.
>
> He does not mean that he would like to have this as the default behavior.
>
> Actually, it will be pity if this will be the default behavior as this 
> will not be inline with TMDM.
>
> If we take the following example:
>
> Tosca -> Opera -> Musical Work -> Work
> (that is, Tosca is an instance of Opera. Opera is subtype of Musical 
> Work. Musical Work is subtype of Work).
>
> We have here two needs:
> 1. Getting the language to work according to the semantics as defined 
> in TMDM (where supertype subtype is transitive relationship). That is 
> Tosca is instance of Opera, but also of Musical Work and of Work. 
> Opera is subtype of Musical Work but also of Work.
> 2. For some use cases, we need to know the direct type or supertype.
>
> On 03-Mar-2011 12:01, Andrew S. Townley wrote:
> > Why can't we leverage existing conventions here and say that the
> > default behavior of the axes is to pull a single level, and then if a
> > modifier is present
>
> How would you call this axis which gives one level only? If you do not 
> include the word "direct" (or something similar), you practically 
> confuse the users: when we ask for "instances" of Work in the above 
> example, we will get nothing - as Tosca is a direct instance of Opera 
> and not or Work. But according to TMDM Tosca is one of the instances 
> of Work. How should we call this one level axis then?
>
> So I think the default behavior should be according to TMDM.
>
> Kind regards,
>
> Rani
>


-- 
Patrick Durusau
patrick-Q/[email protected]
Chair, V1 - US TAG to JTC 1/SC 34
Convener, JTC 1/SC 34/WG 3 (Topic Maps)
Editor, OpenDocument Format TC (OASIS), Project Editor ISO/IEC 26300
Co-Editor, ISO/IEC 13250-1, 13250-5 (Topic Maps)

Another Word For It (blog): http://tm.durusau.net
Homepage: http://www.durusau.net
Twitter: patrickDurusau