Query Set Specification Language (QSSL) Michalis Petropoulos Alin Deutsch Yannis Papakonstantinou UNIVERSITY OF CALIFORNIA, SAN DIEGO

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1 Query Set Specification Language (QSSL) Michalis Petropoulos Alin Deutsch Yannis Papakonstantinou UNIVERSITY OF CALIFORNIA, SAN DIEGO June 2003

2 Exporting DBMSs on the Web XML Web Service XML View Web Service Mediator XQuery XML Web Service XML View DATABASE APPLICATIONS XML Schema Exporting Query Capabilities on the Web Web Services (Function Signatures) Integrating Web Applications Use Web Services Export Query Capabilities Themselves Source Source DATABASE SERVER

3 Overview Query Set Specification Language (QSSL) Describes Parameterized Tree Pattern (TP) Queries Data Services Web Services for Query Capabilities Authoring Interface

4 Motivation for QSSL (I) + name * from to day + leg + from to aircraft Any combination of the following conditions on: the name of the company the origin and destination of one or more (optional) a day of the week the origin of zero or more legs (optional) the destination of zero or more legs (optional) the aircraft used for zero or more legs (optional) The queries may return or elements

5 Motivation for QSSL (II) Web Services published as function signatures: Fixed number of input and output parameters Do not capture the functionality of databases Large number of web services needed One function signature for every parameterized query Do not capture the semantic connections the available functions have with each other and with the underlying databases JDBC Interfaces All possible queries

6 Query Set Specification Language Query Language Tree Pattern Queries: Acyclic XPath expressions consisting of: node tests child axis / descendant axis // predicates [] Widely used in current applications Building blocks of XQuery Excellent visual paradigm for GUIs name = Delta from = JFK to = LAX day = MON leg to = LAS /[name= Delta ]/[from= JFK ][to= LAX ][day= MON ][leg[to= LAS ]]

7 Query Set Specification Language Query Set Specification f 1 f 2 name = Delta =#1 + f 3 f 4 from=#2 to =#3 from = JFK =#2 to = LAX =#3 f 5 day =#4 day = MON =#4 f 6 leg leg f 8 to =#6 to =#6 = LAS day =#7

8 Query Set Specification Language Query Set Specification + name from to day leg + from to * + aircraft f 1 f 1 f 2 f 2 f 3 f 3 + f 2 f 3 + from=#2 f 4 f 5 f 6 * f 4 to =#3 f 4 from=#2 to =#3 f 5 day =#4 f 5 day =#4 f 6 leg * f 6 leg f 7 from=#5 f 7 f 8 f 9 f 8 to =#6 f 7 from=#5 f 9 aircraft =#7 f 8 to =#6 aircraft =#7 Similar to extended context-free grammars f 9

9 Query Set Specification Language Recursive XML Schemas f 1 f 2 familytree person familytree person f 3 name =#1 f 4 place=#2 place =#2 f 5 spouse spouse f 6 name=#3 f 7 place=#4 f 8 children children * person * f 2 person person spouse name =#5 place =#6

10 Query Set Specification Language Recursive XML Schemas f 1 familytree f 1 familytree f f person 2 2 f 2 person f 3 place=#2 f 4 f 5 spouse name=#3 f 3 f 4 f 3 f 4 place=#2 f 5 f 7 f 8 place=#4 children f 2 * f 6 f 7 f 6 f 5 spouse f 6 f 7 name=#3 place=#4 f 8 children f 8 f 2 * QSS of fixed size

11 Data Services View XML Schema Input Message Data Source Data Service WSDL Agent Output Message Data Service = WSDL + QSS A QSS deployed as a web service Exports the XML Schema of an XML view Connects the WSDL calls with the underlying database Receives queries that are encoded by QSS Explicit relationship between input and output

12 Data Services Input Message TPX View XML Schema Data Source Data Service WSDL Input Message Type QSSX Output Message Type XML Schema Agent Output Message XML QSS is translated to XML Schema (QSSX) TP queries that are encoded as XML (TPX) Query result is described by an XML Schema

13 Data Services Reasoning 1. Membership of a query in a data service 2. Subsumption of data services 3. Totality of a data service 4. Overlap of data services QSS can be translated to an equivalent topdown nondeterministic unranked tree automaton Problems are decidable

14 Data Services Authoring Interface

15 Future Work Capability-Based Rewriting User Query TPX Mediator Rewriting Processor Candidate Queries Plan Processor Containing Result Remainder Query Execution Engine Query Result XML Data Service Data Source day = MON f 1 f 2 name = Delta name = Delta f 3 + f 4 from to =#3 from = JFK to = LAX from = JFK to = LAX day day = MON

16 Questions and Answers

17 Query Set Specification Language Example Derivation f 1 f 2 f 3 + f 4 f 5 f 6 * from=#2 to =#3 day =#4 leg f 7 f 8 f 9 from=#2 to =#3 day =#4 leg to =#6

18 Related Work Capability-Based Rewriting Capabilities described as binding patterns Adornments on view attributes Negative approach Expansions of Datalog programs Recursive programs Infinite queries Positive approach