Re: [OWL-S]Avoiding Lists

>If OWL-S ontologies are to be OWL-DL, then we must eliminate all 
>"extraneous" use of the RDF collection vocabulary. (That is, we must 
>only use rdf:List and friends in certain syntactic situations and 
>never as a user level modeling construct.) There are three places 
>where we do or might use collections:
>
>1) As the value of the components property, especially for 
>indicating sequences or unordered sets of processes. Note that 
>simply avoiding subclassing rdf:List isn't sufficient. The mere use 
>of lists puts us in OWL Full.

Restrictions like this were SUCH a bad idea. Sigh. The torture that 
you are now going through illustrates the reasons why.  The entire 
OWL-S process is going to be warped in order to save the tool 
builders the trouble of having to do some intelligent parsing.

>2)  It seems somewhat natural to describe certain parameters as 
>consuming or returning lists of objects.
>
>3) DRS may make use of lists in describing formulas.
>
>Disposing these in reverse order:
>
>3) If DRSyly described preconditions and effect formulas are 
>associated with a process by a datatype property whose values are 
>XMLLiterals that contain the RDF/XML for the DRS formulas, then the 
>parent KB will be in OWL DL even if the literals themselves are OWL 
>Full. I think it would be better if it were DL all the way down, but 
>hey. It's a compromise :)
>
>2) Don't Do That.
>
>1) Don't Do That.
>
>Ok, but what can we do instead of 1 or 2. Some choices:
>
>a) Define a shadow collection vocabulary, e.g., owls:List and 
>friends. Use as one does the RDF collection vocabulary. If one wants 
>compatibility with OWL Full tools, one can define an ontology which 
>contains the requisite equivalences and simply import it when 
>dealing with OWL Full tools. Conversely, it wouldn't be hard to 
>write a lint-esque tool that too OWL Full kbs with modest use of the 
>collection vocabulary that replaces those uses with the 
>corresponding items from the shadow vocabulary. The big loss is that 
>in OWL-DL compatible kbs, you couldn't use the 
>parseType="Collection" short cut (note, you already can't do this 
>for lists of datavalues). Well, boo hoo. We could publish an XSLT 
>sheet that took care of this.
>
>b) Use alternative modeling altogether. For example, for sequences, 
>we can have a sequence object where each owls:item had a 
>distinguishing property value that allowed us to recover the order. 
>It could be a "line number", or a "tag" (as in the surface syntax), 
>or what have you. There'd be some tedium in representing the fixed 
>total number of items and the distinctness of the items, but nothing 
>too bad.
>
>c) Do something exceedingly clever with literals. Literals already 
>*have* structure (both xml and the simpleType, list).
>
>Any thoughts, preferences, screams of pain anyone would like to share?

Thought: Serves you right for trying to fit into OWL-DL

Preference: use option (a). There is almost no semantics associated 
with rdf:List etc. that couldnt be associated with owl:List or even 
fred:List. To hell with parseType, its a crock anyway. Option (b) is 
more work for no perceptible advantage, and option (c) is a Really 
Bad Idea.  Really Really Bad.

Screams of pain: I would be emitting them if I thought that I had to 
use OWL-DL.

Pat

>Cheers,
>Bijan Parsia.


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Received on Tuesday, 3 February 2004 14:23:50 UTC