Path-Based Query Computation by Automated Deduction Peter - PowerPoint PPT Presentation

Path-Based Query Computation by Automated Deduction Peter Baumgartner AG 2 www.mpi-sb.mpg.de/~baumgart/ P. Baumgartner Path-Based Query Computation by Automated Deduction Page 1

Background Deduction Systems ● First-Order ● Classical and Knowledge Representation Logics ● Refutational and Model Computation ● Implementations Applications ● Diagnosis ● Deductive Databases ● Computational Linguistics This Talk ● Computing paths through database schema ● Express task in logic programming framework ● Use “KRHyper” Deduction System ● Connection to AG 5: complements XXL search engine? P. Baumgartner Path-Based Query Computation by Automated Deduction Page 2

A ← (1) KRHyper B  C ← A (2) - Disjunctive logic programs A  D ← C (3) - Stratified default negation false ← A, B (4) - Model computation - Perfect model semantics E ← C, not D - Serious implementation A A A B C B C ✘ ✘ E ✘ ✔ {A,B}  (4) {}  (1) {A}  (2) {A,C}  (1)-(4) - Variant for predicate logic - Extensions: minimal models, abduction, default negation P. Baumgartner Path-Based Query Computation by Automated Deduction Page 3

Description Logics (DL) ● Old-fashioned, problematic graphical notation author PERSON PUBLICATION BOOK ARTICLE and successors: ● ALC PUBLICATION  BOOK  ARTICLE PUBLICATION   author.PERSON ● Corresponds to decidable fragment of first-order logic ● Standard sevices: consistency, classify, retrieve, ... ● The KR formalism for the “Semantic Web” P. Baumgartner Path-Based Query Computation by Automated Deduction Page 4

More DL Language Features PUBLICATION   author.PERSON Class definitions: PUBLICATION   author.PERSON author  creator Subroles: author - / colleague + Inverse/trans. roles: MANYAUTHORS  QVR: (  10 author - ).PUBLICATION Concrete domains: Int, String, ... Nominals: { JAR, JLC }  JOURNAL LISP  {NIL}  ((= 1 CAR).Int  DL language alone and services Cycles: offered by systems do not suffice (= 1 CDR).LISP) to solve task below! ... publication(TACP) Assertions: author(TACP,Knuth) P. Baumgartner Path-Based Query Computation by Automated Deduction Page 5

Application: XML Schema Reasoning Context: Semistructured Data, Schema Integration Task: Determine path based database queries Solution: XPath (?) vs. Query generated from schema P. Baumgartner Path-Based Query Computation by Automated Deduction Page 6

Application: XML Schema Reasoning Generate query: Steps: (1) Schema ➔ DL ➔ If-Then Rules (2) Start and End ➔ Assertions/If-Then Rules (3) Path based query ➔ Computed modell P. Baumgartner Path-Based Query Computation by Automated Deduction Page 7

Application: XML Schema Reasoning publications(X,f(X))  RESEARCHER(X) ARTICLE(f(X))  PUBLICATION(f(X))  MONOGRAPH(f(X))  RESEARCHER(X) (1) Schema ➔ DL ➔ If-Then rules RESEARCHER   publications. (ARTICLE  PUBLICATION  MONOGRAPH) ARTICLE  MONOGRAPH   ... PUBLICATION  BOOK  ARTICLE P. Baumgartner Path-Based Query Computation by Automated Deduction Page 8

Application: XML Schema Reasoning (2) Start and End ➔ Assertions/If-Then rules (Start) RESEARCHER(a)  ← not  X BOOK(X) (End) Solution (almost) trivial! P. Baumgartner Path-Based Query Computation by Automated Deduction Page 9

Conclusions ● Approach taken: - rather inexpressive DL - transformation to logic programming - model computation - purely declarative ● Did not succeed with “standard” Description Logic reasoners, although may be used complementary ● Further issues: - cycles in schema graph - numbers - first-order level reasoning useful? ● Presented first ideas only ... P. Baumgartner Path-Based Query Computation by Automated Deduction Page 10