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SEM, LANG: initial decision tree doc

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 21 Mar 2002 15:15:26 -0500
To: www-webont-wg@w3.org
Message-Id: <20020321151526O.pfps@research.bell-labs.com>
Here is my initial decision tree document.  

Note that it doesn't really have a decision tree in it.  I decided to
format the document slightly differently.

I am looking for comments on additions to this document.  In particular, I
would like more examples of inferences, queries, and syntax possibilities.

peter




		Approaches to OWL


	Options for OWL, as I see it

Syntax 
1. RDF triples, XML dialect, other
2. Can definitional information show up not at top level,
   e.g., john's children are transitive properties?
   
Expressive Power 
3. RDFS
   Frames
   Simple defined classes (e.g., OWL-lite?)
   Powerful DL (e.g., current OWL)

Model Theory 
4. Completely RDF compatible, i.e., interpretations are RDF interpretations
				    with extra conditions
   Mostly RDF compatible, e.g., compatible for individuals
   Not necessarily RDF compatible
5. Can classes or restrictions be inferred, e.g., if John is a Student and
   an Employee does he belong to the intersection of Student and Employee?


	Problematic Points in the Option Space

The combination of 
	1. Syntax is RDF triples
	3. Expressive Power is powerful DL
	4. Model theory is completely RDF compatible
	5. Classes / restrictions are inferrable.
leads to a semantic paradox.  This actually doesn't really depend on the
fact that the syntax is RDF triples, but instead on the fact that rdf:type
is a property and thus can be used in restrictions and on the fact that
loops are possible and thus a form of self-reference is possible.

The use of 
	2. Definitional information can show up not at top level
can lead to difficult, and difficult-to-implement inference.



	Potential Proposals for OWL

DAML+OIL 
  http://www.w3.org/TR/daml+oil-reference
- syntax is RDF triples
- expressive power is powerful DL
- model theory is (close to) RDF model plus additional conditions
- classes / restrictions are not inferrable

D+ : DAML+OIL + theory of classes 
  http://www-db.research.bell-labs.com/user/pfps/webont/dplus.html
- definitional information can show up not at top level
- expressive power is powerful DL
- model theory is RDF model plus additional conditions
- classes / restrictions are inferrable

Old OWL proposal
  http://lists.w3.org/Archives/Public/www-webont-wg/2002Jan/att-0061/01-swol.text
  http://www-db.research.bell-labs.com/user/pfps/webont/swol-rdf.text
- syntax is XML
- definitional information can show up not at top level
- expressive power is powerful DL
- model theory is close to RDF model theory
- classes / restrictions are inferrable

Current OWL proposal
  http://www.cs.vu.nl/~frankh/spool/OWL-first-proposal/  
- syntax is abstract, i.e., other
- all definitional information has to be at top level
- expressive power is powerful DL
- model theory is not the same as RDF model theory
- classes / restrictions are inferrable



	Indicative Inferences, Queries, and Expressiveness

Inference 1-intersection/ 
   Premises: John is an instance of Student
	     John is an instance of Employee
   Conclusion: John is an instance of the intersection of Student and Employee

Inference 2-restrictions/ 
   Premises: John is an instance of Student with no children
   Conclusion: John is an instance of the restriction that requires no children

Query 3-subclasses/ 
   Given: John is an instance of Student with child Joe
   Query: return the subclasses of Student
   Answer Set 1: Student, { John }, Student and Employee, 
		 Student and atleast 79 children, ...
   Answer Set 2: Student

Inference 4-trivial/ 
   Given: John is an instance of Student
   Conclusion: John is not an instance of Student

Syntax 5-embedded def/
   To be said: all John's children are instances of TransitiveProperty,
	       John has a child that is either Joe or Jim
   Meaning: Either Joe or Jim is a transitive property


					SYSTEMS
		DAML+OIL	D+		Old OWL		Current OWL

1-intersection	no		YES		YES		YES

2-restriction	no		YES		YES		YES

3-subclasses	2		1		1		invalid query

4-trivial	no		YES		no		no

5-embedded def	not possible	?		possible	not possible
Received on Thursday, 21 March 2002 15:15:39 GMT

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