Kevin D' Munroe

1
BBQ Blended Browsing and Querying of XML in a
Lazy Mediator System

• Kevin D. Munroe
• Bertram Ludäscher
• Yannis Papakonstantinou
• University of California, San Diego

2
Overview

• Introduction BBQ and MIXm
• BBQ The Interface
• Browsing and Querying with BBQ
• The BBQ API
• Discussion

3
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
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
BBQ and MIXm
BBQ Interface
Interface X
BBQ API
BBQ API
XML Document
XMAS Query
DOM-VXD Interface
Source DTD
MIX Mediator
Source DTD
6
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
BBQ Interface, contd

• Example BBQ Tree
• lt!DOCTYPE Interns
• lt!ELEMENT Interns (Intern)gt
• lt!ELEMENT Intern (name, supervisor, sponsor)gt
• lt!ELEMENT name (PCDATA) gt
• lt!ELEMENT supervisor (PCDATA) gt
• lt!ELEMENT sponsor (CAIDA NPACI UCSD)gt
• lt!ELEMENT CAIDA (ANY)gt
• lt!ELEMENT NPACI (ANY)gt
• lt!ELEMENT UCSD (ANY)gt
• gt

8
BBQ Interface, contd

• 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
BBQ Interface, contd

• Can browse data as DTD-driven list or XML tree

DTD-Driven List
XML Tree
10
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
BBQ Query Session, contd

• 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
BBQ Query Session, contd

• 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
BBQ Query Session, contd

• 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
BBQ Session, contd

• Executing Query and browsing result
• Preview Query...
• UI gt XMAS query string
• Power Users can modify the string
• ...Then Execute
• Result view displayed in Query Body Pane
• Answer tree gt 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
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
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
BBQ API, contd

• A Select-From-Where query using BBQ API
• The DTD
• lt!ELEMENT employees (employee)gt
• lt!ELEMENT employee (name, salary)gt
• The Query
• CONSTRUCT ltoverpaidgt N lt/gt
• WHERE ltemployeesgtltemployeegt
• Nltname/gt ltsalarygt OP lt/gt lt/gt
  lt/gt
• AND OP gt 30000

18
BBQ API, contd

• function simpleBBQClient()
• boolean required true
• bbqSession lt- new BBQSession()
• bbqSession.connect()
• String list bbqSession.getListOfDataSources()
  
• src bbqSession.openDataSource(listemployees)
• bbqSession.setSourceConstraint(salary,gt,
  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.create
  XMASQuery())

19
BBQ API, contd

• function simpleBBQClient()
• boolean required true
• bbqSession lt- new BBQSession()
• bbqSession.connect()
• String list bbqSession.getListOfDataSources()
  
• src bbqSession.openDataSource(listemployees)
• bbqSession.setSourceConstraint(salary,gt,
  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.create
  XMASQuery())

20
BBQ API, contd

• function simpleBBQClient()
• boolean required true
• bbqSession lt- new BBQSession()
• bbqSession.connect()
• String list bbqSession.getListOfDataSources()
  
• src bbqSession.openDataSource(listemployees)
• bbqSession.setSourceConstraint(salary,gt,
  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.create
  XMASQuery())

21
BBQ API, contd

• function simpleBBQClient()
• boolean required true
• bbqSession lt- new BBQSession()
• bbqSession.connect()
• String list bbqSession.getListOfDataSources()
  
• src bbqSession.openDataSource(listemployees)
• bbqSession.setSourceConstraint(salary,gt,
  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.create
  XMASQuery())

22
BBQ API, contd

• function simpleBBQClient()
• boolean required true
• bbqSession lt- new BBQSession()
• bbqSession.connect()
• String list bbqSession.getListOfDataSources()
  
• src bbqSession.openDataSource(listemployees)
• bbqSession.setSourceConstraint(salary,gt,
  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.create
  XMASQuery())

23
Further Information

• MIX project
• http//www.npaci.edu/DICE/MIX/
• BBQ
• http//www.npaci.edu/DICE/MIX/BBQ