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Review of Requirements Document

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 1 Jan 2003 13:35:59 -0500
Message-Id: <p05200f43ba38e1707de7@[]>
To: webont <www-webont-wg@w3.org>

Review of WD version of requirements document

1. I don't know if LC documents contain a "change from last version" 
section - if appropriate, be sure to update (bookkeeping comment only)

2. As discussed, some of our requirements were not met and should be 
demoted - I  believe Jeff is on top of this.  However, the following 
is how we specified R12, Unique names assumption:

>R12. Local unique names assumptions
>In general, the language will not make a unique names assumption. 
>That is, distinct identifiers are not assumed to refer to different 
>objects (see the previous requirement). However, there are many 
>applications where the unique names assumption would be useful. 
>Users should have the option of specifying that all of the names in 
>a particular namespace or document refer to distinct objects.

I believe we have actually met this if we accept the allDifferent (or 
allDistinct) construct.  I realize this means listing the names in 
the namespace to specify they are unique, but in fact the above 
doesn't state that one shouldn't have to do this.  I consider it like 
where RSS requires the listing of channels, even if they're defined 
in a document, because you both have to have the definitions AND the 
statement that they are to be used.  I thus think it could be argued 
that we should leave R12 as a requirement (I do not feel strongly on 

3. R13 is that we have a way that statements can be "tagged" (quotes 
in the document) with additional information, and stating RDF 
reification may be a way to achieve it.  I believe we have achieved 
this objective only in allowing RDF tagging to be added to our 
graphs, and Jeremy has recently raised some points about whether the 
RDF Graphs that would be produced would be in the OWL syntax for Lite 
or DL documents.   If this is true, we may not have fully met our 
tagging requirement

4. R19, R20 - I believe these are met through RDF, but someone needs 
to check. (R18 is clearly met by rdf:label)

5. We actually have reached a couple of our objectives - perhaps if 
we can demote requirements we could consider promoting objectives? 
If so, I would argue we might move the following to requirements:

>O1. Layering of language features
>The language may support different levels of complexity for defining 
>ontologies. Applications can conform to a particular layer without 
>supporting the entire language. A guideline for identifying layers 
>may be based on functionality found in different types of database 
>and knowledge base systems.

we clearly achieved this.

>O6. Effective decision procedure
>     The language should be decidable.

We have defined a decidabe and efficient subset of our language (OWL 
Lite), and a decidable subset (OWL DL).  I believe this could allow 
us to move 06 to a requirement that read more like follows:

Rxx. Effective Decision procedure

   Many applications may require specific application guarantees for 
reasoners including decidability with an effective decision procedure 
or just decidability.  Although general ontology reasoning is 
undecidable, subsets can be defined which have these types of 
specific guarantees, and the Web ontology language should identify 
and support such subsets.

[note, Ian or someone might want to fix my wording above if I didn't 
get the details right]

Professor James Hendler				  hendler@cs.umd.edu
Director, Semantic Web and Agent Technologies	  301-405-2696
Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)
Received on Wednesday, 1 January 2003 13:36:04 UTC

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