Consistency Checking of Semantic Web Ontologies

looneyvillebiologistInternet και Εφαρμογές Web

21 Οκτ 2013 (πριν από 3 χρόνια και 10 μήνες)

74 εμφανίσεις

1

Consistency Checking

of Semantic Web Ontologies

Kenneth Baclawski, Northeastern U. & VIS

Mieczyslaw M. Kokar, Northeastern U. & VIS

Richard Waldinger, SRI & Kestrel

Paul A. Kogut, Lockheed Martin


2

Overview


Inconsistency


UBOT Tools


ConsVISor


Snark


Conclusions


Future directions

3

Consistency

con

sis

ten

cy

agreement with what has already been done or expressed;

conformity with previous practice

[Webster]



In logic: from
P

and
not(P)

can derive anything

Inconsistency is a dangerous thing for autonomous agents!



An inconsistent ontology means one part of the


ontology does not agree with another

4

Logical Consistency


Definition:
there exists a non
-
trivial model of the theory
.


If a theory is inconsistent then every logical statement can
be proven true.



Our Opinion:


One consistent ontology for Semantic Web


impossible


Consistent subsets of a set of ontologies


but need to know
when a given set is inconsistent


need warnings


Every single ontology should be consistent


need checking


5

Inconsistent Ontology: Example



Recursive combination of expressions



Elementary


constants, variables



Operation


includes operators (e.g., +, *)



Example: (x + y + 5)*(z + 3)*(a + b)



Problem:



at least twice more Operations than Expressions (cardinality constraint)



more Expressions than Operations (subClass constraint)



#Expression


#Operation


2*#Expression


inconsistency?



Operation


either empty or infinite!



Mistake: cardinality restrictions inverted (not uncommon)

(UML syntax)

6

What’s wrong with this ontology?

7

[Enzyme]


子牯瑥楮崠


孃[敭楣慬崠


孒敡捴楯i]
<
孅湺y浥崠

周畳u䕮Ey浥
<
䕮Ey浥!

[…]


class cardinality

8

UBOT
-

Ontology Engineering Tools

DAML Ontology

Engineer

DAML

ontologies

UML GUI

Consistency Reasoning Agent








CRAVE

Consistency

checking

results

UML DAML

Translation


XMI

models

DAML

ontologies

Consistency

checking

results

ConsVISor

Specware

SNARK

DAML

ontologies

DAML

ontologies

BugVISor

9

ConsVISor


Input: URI for DAML ontology or annotation


Processing: Prolog
-
based tool that checks ontologies
against the DAML+OIL axiomatic semantic specification


Output: list of error and warning messages


Role:


help ontology engineers check ontologies


help website developers check DAML annotations


Cannot check consistency of the language (DAML)

10

ConsVISor Architecture

DAML

file

daml20.pl

Modified

daml20.pl

Final

Messages

Messages

d2p

Prolog

p2d

11

Num

ID

Message

1:

0034

The classes http://quantlabs.com/vis/ont/vehicle.daml#
WaterCraft

and
http://quantlabs.com/vis/ont/vehicle.daml#
LandVehicle

were declared to be
disjoint
, but
they
both contain

http://quantlabs.com/vis/ont/vehicle.daml#
avk3379
.

12

SNARK/Specware


Specware (from Kestrel Institute)


Formal specifications


Based on category theory


SNARK (from SRI)


Theorem prover (resolution, paramodulation, special
unification, sorts, procedural attachments,
extensibility with Lisp)


But may not terminate (when ontology is consistent)


Can check consistency of the language specification!


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Example (SNARK)


(<=> (Type ?fp FunctionalProperty)


(and (Type ?fp Property)


(=> (and (PropertyValue ?fp ?s ?v1)


(PropertyValue ?fp ?s ?v2))


(= ?v1 ?v2))))


(<=> (Type ?fp FunctionalProperty)


(and (Type ?fp Property)


(
forall
(?s ?v1 ?v2)


(=> (and (PropertyValue ?fp ?s ?v1)


(PropertyValue ?fp ?s ?v2))


(= ?v1 ?v2)))))

Original axiom:

Revised axiom

Checking Consistency of DAML Axiomatization



With the original axiom every property is functional



Consequently, since rdf:Bag is both rdfs:Class and rdf:Resource


rdfs:Class = rdf:Resource

14

Checking
Restriction

w/SNARK


daml:Restriction was used to state that one can have only
one father (see [1])


SNARK was able to prove that there is at least one father
for everybody


But could not prove that there are no more than one


The problem was in the DAML specification of cardinality
restriction


Specification has been revised


[1] www.daml.org/2001/03/daml+oil
-
walkthru.html

15

Conclusion


Inconsistencies are not desirable although not easy to avoid


It’s better to identify them and then decide how to treat them
rather than ignore


ConsVISor is available at
http://vis.home.mindspring.com

for
checking consistency of your DAML ontologies


Can be used to find problems in an ontology, not
necessarily inconsistencies and not necessarily all


SNARK can find more, but will quit after some time


SNARK can be used to check language specifications

16

Current/Future Work

Ontology

Or

Annotated Source

DAML

Axioms

ConsVISor

Bug

Locations

Explanations

BugVISor

Errors

DAML

Bug

Ontology

17

Current/Future Work (cont.)


Integrate ConsVISor with Snark


Investigate ways to address time complexity of
consistency checking


Make the integrated tool available on the web


Analyze errors due to merging different ontologies


Provide quantitative evidence of problems related
to inconsistencies