Ling Wang, Mukesh Mulchandani Advisor: Elke A. Rundensteiner Rainbow Research group, DSRG, WPI

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Ling Wang, Mukesh MulchandaniAdvisor Elke A.
Rundensteiner Rainbow Research group, DSRG, WPI
Updating XQuery Views over Relational Data
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Motivation

• XML is a standard for information exchange over
  internet
• But RDBMS is mature
• - Mature query optimization techniques
• High query performance
• Research topic on dealing with XML using
  relational technology
• - Publishing XML over relational database
• SilkRoute (ATT), XPERANTO (IBM), RAINBOW(WPI)
• - Storing XML into RDBs
• LegoDB (BellLab), RAINBOW (WPI)
• Support Update features is important next step
  for those system
• Our Work will focus on Content updates using
  XQuery language

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Problem Definition

• Sub-Problem 1 Expressing updates in XQuery
• We need to
• - Extension to XQuery
• - Extension to XML query Parser to support
  Update features
• Sub-Problem 2 Translate XQuery update on
  Virtual View into SQL update on RDB
• We need to
• - Mapping from XML with Relational data model
  ---- detecting View Updatability
• - Mapping XQuery update on virtual
  view into SQL update on Relational table ----
  update translation

XQuery Update
XML View
View Query
SQL Update
RDBMS
RDBMS
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Solution for sub-problem1 Query Update Grammar
  FOR binding1 IN Xpath-expr,.. LET binding
Xpath-expr, WHERE predicate1,.. updateOp,
   Where updateOp is defined as     UPDATE
binding subOp , subOp and subOp is
  DELETE child RENAME child To new_name
INSERT ( bind BEFORE AFTER child
new_attribute(name, value) new_ref(name,
value) content BEFORE AFTER child )
REPLACE child WITH ( new_attribute(name,
value) new_ref(name, value) content
) FOR sub_binding IN Xpath-subexpr,.. WHERE
predicate1,. updateOp.
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Solution for sub-problem2 Update Translation

• Four aspect have to be explored
• Correct Update Translatability Definition
• General Classification of XML View Update(XVUP)
• View Updatability Detecting
• Valid Update Translation

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Correct Update Translatability

• No side effect
• One Step changes
• - Each database tuple is affected by at most one
  step of update operation
• - Implications No order between update
  operation
• Could affect same table several times
• Minimal changes
• - No valid translation is subset of current
  translation
• - No extraneous updates
• Replacement can not be simplified
• - Two replace could get same result, pick simple
  one
• - Replace the minimum attribute set
• No insert-delete pairs
• - Replace is cheaper than Insert/Delete pair

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Information
Language
Instance
Integrity Constraints (Key, FK)
Aggregation
1NF
Recursion
Local Constraints (Not Null, domain)
Hierarchy Consistency
2NF
RDB Schema
Correlation predicates attributes exposition
3NF
Underlying Relation
Non Correlation predicates attribute exposition
BCNF
Key Exposition
Virtual View Definition
Duplicates
Deletion
Insertion
Replacement
Rename
Move
Set of each
Modification
Group Update
Schema Change
General Classification of XQuery View Update
Problem Space
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View Updatability
View Features View Features View Features Update Type Update Type
Exposition complete Consistency No Duplication Complete Update Partial Update
Y Y Y Y Y
Y Y N Y Case 1
Y N Y Y Case 2
Y N N Y Case 3
N Y Y N N
N Y N N N
N N Y N N
N N N N N
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Case study for View Updatability

• Case 1 Complete Exposition Consistent
  Duplication
• Partial update touch duplication is not
  translatable
• Case 2 Complete Exposition In-Consistent
  No-Duplication
• sub-tree rooted at inconsistent edge is not
  updatable
• Case 3 Complete Exposition In-Consistent
  Duplication
• - case2 ? case 3, same as case 2 for
  inconsistent part
• - partial update touch duplication is not
  translatable

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Valid Update Translation
XQuery
View
Parser
View Analyser
Translatability Checker
Valid Update Checker
Update Decomposer
Update Propagation
Translator
SQL Update
DB
Trigger
Execution Engine