drago: distributed reasoning architecture for the semantic web
DESCRIPTION
DRAGO: Distributed Reasoning Architecture for the Semantic Web. Andrei Tamilin and Luciano Serafini. S econd European Semantic Web Conferece (ESWC'05) Heraklion, Greece. 1 June 2005. Work is supported by. Talk outline. Motivation and vision Distributed Description Logics (DDL) - PowerPoint PPT PresentationTRANSCRIPT
DRAGO: Distributed Reasoning Architecture for
the Semantic Web
Andrei Tamilin and Luciano Serafini
Work is supported by
1 June 2005
Second European Semantic Web Conferece (ESWC'05)Heraklion, Greece
June 01, 2005 A. Tamilin and L. Serafini
Talk outline
• Motivation and vision
• Distributed Description Logics (DDL)
• Distributed tableau for reasoning in DDL
• DRAGO reasoning architecture
June 01, 2005 A. Tamilin and L. Serafini
MotivationWhere we start:• Steady ontology proliferation• Heterogeneity is inevitable • How to achieve interoperability
Interoperability bridge:• Semantic mappings• Reasoning support
Goal:• Provide reasoning for ontology
space (ontologies interrelated by mappings)
June 01, 2005 A. Tamilin and L. Serafini
Global reasoning visionCompile a global ontologyand reason with existing DL
tools
• Benefits:– Stable theory and tools of
DL
• Drawbacks:(i) non-scalability(ii) losing language and
reasoning specificity(iii) losing privacy and
autonomy of ontological knowledge
June 01, 2005 A. Tamilin and L. Serafini
Distributed reasoning vision
Reasoning through a combination, via mappings, of distributed local reasoners
• Benefits:(i) scalable(ii) respects language specificity(iii) supports information hiding
Revisited goal:• Provide a distributed
reasoning for ontology space
June 01, 2005 A. Tamilin and L. Serafini
Requirements / Our proposals
• Formal framework to represent ontology space– Distributed Description Logics
• Extension of DL
• Define a suitable decision procedure– Distributed tableau algorithm
• Extension of DL tableau
• Implement the reasoning procedure– DRAGO reasoning system
• Extension of Pellet OWL DL reasoner
Requirements / Our proposals
June 01, 2005 A. Tamilin and L. Serafini
DDL syntax• DDL is a family of description logics {DLi}iI
• A bridge rule from i to j is an expression of the form:
where X and Y are concepts of DLi and DLj.
• A distributed T-box (DTB) is a pair {Ti}iI, {Bij}ijIwhere Bij is a collection of bridge rules from i to j
i:X j:Y (into-bridge rule)
i:X j:Y (onto-bridge rule)
June 01, 2005 A. Tamilin and L. Serafini
Bridge graph
A bridge graph of a DTB
T1
T2
T3
T4T5
T6
T7B12
B23
B34
B54
B56
B64
June 01, 2005 A. Tamilin and L. Serafini
DDL semanticsA distributed interpretation (DI) of a DTB
{Ii}iI, {rij}ijI
• Ii is a local interpretation of Ti on a local domain Ii
T1, T2, T3, T4, T5, T6, T7
I1, I2, I3, I4, I5, I6, I7
• rij is a domain relations from I to j
rijIi x Ij
June 01, 2005 A. Tamilin and L. Serafini
DDL satisfiability
DI={Ii}iI,{rij}ijI satisfies DTB={Ti}iI,{Bij}ijI DI DTB
If
• all Ti are satisfied
• all bridge rules Bij are satisfied
June 01, 2005 A. Tamilin and L. Serafini
Into-bridge rule satisfiability
rij
Xr12(X)
YIi Ij
i:X j:Y
rij(xIi) YIj
DI
June 01, 2005 A. Tamilin and L. Serafini
Onto-bridge rule satisfiability
rijX
r12(X)Ii Ij
rij(xIi) YIj
i:X j:Y
Y
DI
June 01, 2005 A. Tamilin and L. Serafini
Subsumption propagation in DDL
T1 T2
A
B H
G
isA isA
Directionality property: Knowledge propagates ONLY along the direction of bridge rules!
GI2 r12(AI1) r12(BI1) HI2
DTB = T1, T2, B12
DTB
June 01, 2005 A. Tamilin and L. Serafini
Generalized subsumption propagation
Ti TjA
B1 H1
G
B2
Bn
…H2
Hn
…
DTB j:G H1 … Hn
DTB={Ti}iI,{Bij}ijI
DTB i:A B1 … Bn
June 01, 2005 A. Tamilin and L. Serafini
Soundness and completeness
Let DTB12 = T1, T2, B12 be a distributed T-box
Bridge operator encapsulates propagated axioms
B12(T1) = 1:A 2:G B12G Hkk=1
n
A Bkk=1
n
T1
1:Bk 2:Hk B12for 1 k n, n 0
Theorem
DTB12 2:X Y T2 B12(T1) X Y
June 01, 2005 A. Tamilin and L. Serafini
Basic reasoning service of DDL
DTB i:C D
Restrictions:
(1) bridge graph is cycle-free
(2) bridge rules connect atomic concepts
(3) no nominals
DTB i:X
i:X is satisfiable with respect to DTB • if there exist a DI such that DI DTB • and XIi0
June 01, 2005 A. Tamilin and L. Serafini
Distributed tableau intuition
DTabi(X) = Tabi(X) + “lazy computation of bridge operator”
DD
D
D
D D
DTab6(X)
Tab1(X)
Tab2(X)Tab7(X)
Tab3(X)
Tab5(X) Tab4(X)
June 01, 2005 A. Tamilin and L. Serafini
Distributed tableau intuition
x L(x) = {D}
Standard tableauexpansion rules
y L(y) = {G, … H1 H2}
DTabj(D)DTabi(A (B1 B2))
Bij
L(z) = {A (B1 B2)} z
i:B1 j:H1
i:A j:G
i:B2 j:H2
Is j:D is satisfiable wrt DTB?
}Clash
G H1 H2
A (B1 B2)
June 01, 2005 A. Tamilin and L. Serafini
Algorithm formalizationDTabj
• SHIQ-tableau expansion rules +
• “bridge” expansion rule:
If 1. GL(x), , and
2. B {B
H {H , and
DTabi(A B) = Unsatisfiable for some H L(x),then L(x) L(x) { H}
i:A j:GBij
i:B j:HBij
June 01, 2005 A. Tamilin and L. Serafini
Algorithm properties
Theorem (Termination) For any acyclic distributed T-box and for any SHIQ concept X, DTabj(X) terminates.
Theorem (Soundness and completeness) j:X is satisfiable in distributed T-box if and only if DTabj(X) can generate a complete and clash-free completion tree.
June 01, 2005 A. Tamilin and L. Serafini
Distributed reasoning architecture
URI1
URI2
URI3
URI4
URI5
URI6
URI7
B37
B67
RP1
RP2
RP3
June 01, 2005 A. Tamilin and L. Serafini
Implementation
• OWL ontologies
• C-OWL semantic mappings
• Distributed Reasoner is an extension to open source OWL Reasoner Pellet
June 01, 2005 A. Tamilin and L. Serafini
Conclusions
• Overviewed DDL formal framework for representing ontologies and mappings
• Described subsumption in DDL
• Introduced sound and complete decision procedure for cycle-free DDL
• Implemented a reasoning prototype, DRAGO,
http://trinity.dit.unitn.it/drago