[sc34wg3] TMCL: 4.4.1 Topic Type Constraint

Robert Barta rho at devc.at
Thu Feb 14 03:37:55 EST 2008

On Thu, Feb 14, 2008 at 07:40:53AM -0000, Graham Moore wrote:
> >> How is 4.4.1. to be understood? 
> >>  "..only topics  ... defined as topic types can have instances"
> >> What about association types, occurrence types and name types? They
> >> definitely need to be "topics allowed to have instances".
> Firstly, this is a map wide constraint.

Yes, many constraints in TMCL are map wide.

> It is trying to say that if a topic plays the role of type in the
> type-instance association and it is NOT an instance of the topic
> tmcl:topic-type that the given type topic violates the topic type
> constraint. 

> .... The evaluation function knows the topic of topic-type (its
> defined in TMCL) and can thus derive the list of all topic types at
> evaluation time.

Hmm, 4.1. says that "Constraints are independent from each other....",
but obviously TMCL somehow makes a distinction between allowing to say

     "Person isa tmcl:topicType"

and the actual TopicTypeConstraint which is sort-of hovering in the
background. I didn't get this from the text. But my interpretation

>   uniq ( // tm:topic >> types ) -- // tmcl:topicType == null

would then reflect this. Good.

> I'm not sure I follow the bit about having to adopt the tmrm-tmdm
> mapping stuff. TMCL aims to be self contained in terms of TMDM and
> TMRQL. Given we can identify the topic-type topic we don't need the
> tm:topic in order to formulate the query.

Well, TMQL _has_ to use TMDM and needs hooks to get access to the
innards of a map.

> Hope this starts to clear some things up.

We still have to say something about making the fact

     Person isa tmcl:topicType

accessible to the TMQL processor which effectively checks the map.

Austrian Research Centers, Environmental Monitoring Systems

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