1. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure Kevin D. Munroe Bertram Ludäscher Yannis Papakonstantinou University of California, San Diego BBQ: Blended Browsing and Querying of XML in a Lazy Mediator System

2. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure Overview Introduction: BBQ and MIXm BBQ: The Interface Browsing and Querying with BBQ The BBQ API Discussion

3. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure Introduction (preaching to the choir) XML as a universal data exchange format and model MIX (Mediation of Information using XML) project at UCSD/SDSC MIX mediator (MIXm) integrated views of XML data sources XMAS query language lazy query evaluation with DOM-VXD (EDBT 2000) Features of a MIXm client simplify query construction intuitive XML browsing flexible interface

4. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ 2.0 BBQ = User Interface + API package BBQ Interface features Schema-driven browsing of XML Intuitive drag-and- drop query formulation Iterative Query refinement History BBQ API cross-platform (Java) based on well- known Java 2 APIs

5. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure XMAS Query DOM-VXD Interface MIX Mediator BBQ Interface BBQ API Interface X BBQ API XML Document XML Data Source Source DTD BBQ and MIXm

6. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure The BBQ Interface DTDs are represented by trees non leaf nodes= elements leaf nodes = character content Nodes are rendered based on type Wildcards are also displayed

7. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ Interface, cont’d Example BBQ Tree <!DOCTYPE Interns [ ]>

8. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ Interface, cont’d Query Body Panel contains multiple data sources Query Head Panel has a “hook” for building up projected elements Query Body Panel Query Head Panel

9. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ Interface, cont’d Can browse data as DTD-driven list or XML tree XML Tree DTD-Driven List

10. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure A BBQ Query Session Query Sessions consist of one or more query cycles A query cycle is delineated by executing a query BBQ maintains history across query cycles XMAS queries syntax: CONSTRUCT head WHERE body

11. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ Query Session, cont’d Begin by opening XML data source Select data source from list BBQ application can open arbitrary data sources Browse data source by DTD or XML tree If document has no DTD, BBQ derives one DDbE from IBM AlphaWorks XML data source is sample data

12. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ Query Session, cont’d Setting Conditions “Set-Required”- requires existence Binary operations applied to leaf nodes operators are in pulldown list; set one or more conditions Setting Joins Copy/Paste one leaf node onto the other Join format equality other binary operators (theta-join)

13. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ Query Session, cont’d Constructing the Head Use Data Source Elements Drag/Drop elements from Query Body Panel to Query Head Panel XMAS semantics requires at most one top-level element Set a group-by Simple Group-by - group by the selected node Complex Group-by - group by other nodes in the body Created in Query Head Panel Paste from Query Body Panel

14. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ Session, cont’d Executing Query and browsing result Preview Query... UI => XMAS query string “Power Users” can modify the string...Then Execute Result view displayed in Query Body Pane Answer tree => result view DTD If error occurs BBQ reverts to state prior to Execute No results? BBQ saves XMAS query string so users can debug

15. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ Query Session- Complete Browse the result view BBQ Derives text DTD for view View contents materialized using DOM-VXD interface Views can be constructed on top of result view

16. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure The BBQ API BBQ API = package of Java classes BBQ Interface is a client of BBQ API API client is handed the same data structures that BBQ manipulates internally XML/DTD data structures based on TreeNode class. Clients keep local copies of data structures

17. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ API, cont’d A Select-From-Where query using BBQ API The DTD: The Query: CONSTRUCT [ $N ] WHERE $N: $OP AND $OP > 30000

18. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ API, cont’d function simpleBBQClient() { boolean required = true; bbqSession <- new BBQSession(); bbqSession.connect(); String []list = bbqSession.getListOfDataSources(); src = bbqSession.openDataSource(list[employees]); bbqSession.setSourceConstraint(salary,’>’, “30000”); ans = bbqSession.getAnswerTree(); bbqSession.addNewAnswerTreeNode(ans, BBQSession.kNodeTypeElement, null, “overpaid”); bbqSession.addAnswerTreeNode(ans.child(0), name, required); bbqSession.setGroupBySimple(ans.child(0),required); answer = bbqSession.executeXMASQuery( bbqSession.createXMASQuery()) }

19. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ API, cont’d function simpleBBQClient() { boolean required = true; bbqSession <- new BBQSession(); bbqSession.connect(); String []list = bbqSession.getListOfDataSources(); src = bbqSession.openDataSource(list[employees]); bbqSession.setSourceConstraint(salary,’>’, “30000”); ans = bbqSession.getAnswerTree(); bbqSession.addNewAnswerTreeNode(ans, BBQSession.kNodeTypeElement, null, “overpaid”); bbqSession.addAnswerTreeNode(ans.child(0), name, required); bbqSession.setGroupBySimple(ans.child(0),required); answer = bbqSession.executeXMASQuery( bbqSession.createXMASQuery()) }

20. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ API, cont’d function simpleBBQClient() { boolean required = true; bbqSession <- new BBQSession(); bbqSession.connect(); String []list = bbqSession.getListOfDataSources(); src = bbqSession.openDataSource(list[employees]); bbqSession.setSourceConstraint(salary,’>’, “30000”); ans = bbqSession.getAnswerTree(); bbqSession.addNewAnswerTreeNode(ans, BBQSession.kNodeTypeElement, null, “overpaid”); bbqSession.addAnswerTreeNode(ans.child(0), name, required); bbqSession.setGroupBySimple(ans.child(0),required); answer = bbqSession.executeXMASQuery( bbqSession.createXMASQuery()) }

21. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ API, cont’d function simpleBBQClient() { boolean required = true; bbqSession <- new BBQSession(); bbqSession.connect(); String []list = bbqSession.getListOfDataSources(); src = bbqSession.openDataSource(list[employees]); bbqSession.setSourceConstraint(salary,’>’, “30000”); ans = bbqSession.getAnswerTree(); bbqSession.addNewAnswerTreeNode(ans, BBQSession.kNodeTypeElement, null, “overpaid”); bbqSession.addAnswerTreeNode(ans.child(0), name, required); bbqSession.setGroupBySimple(ans.child(0),required); answer = bbqSession.executeXMASQuery( bbqSession.createXMASQuery()) }

22. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure BBQ API, cont’d function simpleBBQClient() { boolean required = true; bbqSession <- new BBQSession(); bbqSession.connect(); String []list = bbqSession.getListOfDataSources(); src = bbqSession.openDataSource(list[employees]); bbqSession.setSourceConstraint(salary,’>’, “30000”); ans = bbqSession.getAnswerTree(); bbqSession.addNewAnswerTreeNode(ans, BBQSession.kNodeTypeElement, null, “overpaid”); bbqSession.addAnswerTreeNode(ans.child(0), name, required); bbqSession.setGroupBySimple(ans.child(0),required); answer = bbqSession.executeXMASQuery( bbqSession.createXMASQuery()) }

23. San Diego Supercomputer Center National Partnership for Advanced Computational Infrastructure Further Information MIX project http://www.npaci.edu/DICE/MIX/ BBQ http://www.npaci.edu/DICE/MIX/BBQ