[sc34wg3] Possible TMRM issue

[Lars Marius Garshol]

* Patrick Durusau
>
> Puzzled by your comment "...may have to traverse the entire model  
> every time you want to compare two proxies."
>
> The TMRM specifies the required starting condition of being a set  
> of proxies, i.e., no duplicates, but it does not constrain how an  
> implementation would meet that condition.

No, and that's fine.

> How duplicates would be detected would depend upon the method  
> chosen for implementation. Even though set comprehension is  
> specified, sets are not necesssarily implemented as sets. Such  
> implementations must, however, meet the test specified by the set  
> comprehension requirement. Really depends on what a particular  
> legend requires or permits in terms of structure as to what method  
> one would use.
>
> Does that help?

No. :-)

The problem is that it's far from obvious how this can be done  
without having to traverse the entire model every time a change is  
made, or, alternatively, every time you want to compare two proxies.  
What we need is some kind of reassurance that it is *possible* to  
implement this efficiently. If it's not possible to do this  
efficiently I don't think the current model is acceptable at all, and  
if only Robert knows how to do it I'm afraid we'll only ever see one  
implementation of this (Robert's).

--
Lars Marius Garshol, Ontopian               http://www.ontopia.net
+47 98 21 55 50                             http://www.garshol.priv.no