NavigationDriven Evaluation of Virtual Mediated Views

1
Navigation-Driven Evaluation of Virtual Mediated
Views
Bertram Ludäscher, SDSC/UCSD Yannis
Papakonstantinou, UCSD Pavel Velikhov, UCSD

• Overview
• Mediator architecture for virtual XML documents
  
• Navigation-driven evaluation lazy mediators
• XMAS QL and algebra
• Mismatch DOM-VXD vs. source granularity
• Conclusions

2
Mediator Architecture for Virtual XML Documents
(DOM-VXD)
Client Query
Integrated XML View
3
Mediator Architecture for Virtual XML Documents
(DOM-VXD)
Client Query
MIXm Mediator
4
Navigating Virtual Views

• Mediator approaches
• warehousing
• virtual
• compute complete answer
• compute partial answer on demand, i.e., driven
  by the client navigations

5
Navigation-Driven Evaluation Lazy Mediators
Input client navigations
view definition ans q( s1 sn )
result
Lazy Mediator
Output source navigations
s1
sn
...
XML source
XML source
6
Navigation-Driven Evaluation Lazy Mediators
Input client navigations
view definition ans q( s1 sn )
result
Lazy Mediator
Output source navigations
s1
sn
...
XML source
XML source
7
Navigation-Driven Evaluation Lazy Mediators
Input client navigations
view definition ans q( s1 sn )
result
Lazy Mediator
Output source navigations
s1
sn
...
XML source
XML source
8
Navigation-Driven Evaluation Lazy Mediators
Input client navigations
view definition ans q( s1 sn )
result
Lazy Mediator
Output source navigations
s1
sn
...
XML source
XML source
9
Navigation-Driven Evaluation Lazy Mediators
Input client navigations
view definition ans q( s1 sn )
result
Lazy Mediator
Output source navigations
s1
sn
...
XML source
XML source
10
Modeling Navigations

• Navigational commands (subset of DOM API)
• d (down)
• r (right)
• f (fetch)

p0
d
Navigations c1(p0), c2(p1), ,
cn(pn-1) (pj ci(pi-1), i lt j)
p1
d
r
r
r
p4
f
d
d
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Query Processing
XMAS Query
XMAS View Definition
Translator
Algebraic Plan for the Query
Algebraic Plan for the View
Composition (qov)
Composed Algebraic Plan
Rewriter/Optimizer
Compile-time
Optimized Plan
Run-time lazy VXD evaluation
Plan Execution
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XMAS Queries (XML Matching And Structuring
Language)
CONSTRUCT ltbooksgt
ltbookgt a1 t ltpubsgt
p p
lt/pubsgt
lt/bookgt a1, t
lt/booksgt WHERE ltbooks.bookgt a1 ltauthor
/gt t lttitle /gt lt/gt IN "amazon.com" AND
ltauthors.authorgt a2 ltauthor /gt ltpubsgt p
ltpub/gt lt/gt lt/gt IN "www...DBLP " AND value(
a1 ) value( a2 )
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XMAS Algebra
createElementbook, list -gt Res
Concata1, t,eps-gt list
createElementpubs,ps-gteps
removeDuplicatesa1, t
groupBya1 ,t,p-gtps
val(a1)val(a2)
getDauth,pubs.pub-gtp
getDbook,title-gtt
getDauth,name-gta2
getDbook,author-gta1
getDamazon,books.book-gtbook
getDDBLP,authors.author-gtauth
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XMAS Algebra

• relational operators
• XML specific ones (? nest, unnest pes)
• works on trees of variable bindings

createElementname,ch-gte createListname,ch-gte conca
tenatel1lk-gtz groupBya1gk,v-gtl getDescendent
se,pe-gtch getNamee-gtname assignfu1un,v1vn-gtx
mapfu1un,v1vn-gtx1xn
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Lazy Mediator Example
answer book author Peter XML
for pubs
book book author
Mary All about pubs
Value(A1)Value(A2)
BOOKS A1 T Peter XML for smarties Mary
All about XML
DBLP A2 P Peter ltpubsgtlt/pubsgt Mary
ltpubsgtlt/pubsgt
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Efficiency of Lazy Mediators

• Bounded Browsable bounded of source
  navigations
• Browsable does not require accessing all
  elements of lists
• Unbrowsable may require accessing all elements
  of lists
• (depend on the given navigation commands!)

Navigational Complexity
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Optimizing Using Navigational Complexity
Potential for optimization of unbrowsable
sub-parts
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Granularity of Navigations
Mismatch Source granularity lt!gt DOM-VXD
granularity (RDB sets of tuples vs.
individual table cells) gt source should control
result granularity gt generic buffer component
(above the wrapper) based on LXP (Lean XML
Fragment Protocol)
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LXP Protocol
Buffer requests

• getRoot
• get a holeId (handle) for the root node
• fillHole( holeId )
• replaces the hole in the open XML tree with a
  list of nodes and possibly further holes

open XML tree
20
Some Empirical Results Selection Queries

21
Performance Evaluation Construction Queries
328 homes x 122 schools
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Summary Conclusions

• Demand-driven evaluation of virtual XML views
• related to relational iterators and pipelines
  (but trees vs tables, multiple vs single
  continuations)
• XMAS QL and algebra for XML
• (try some XMAS-BBQ demo 14)
• http//www.npaci.edu/DICE/MIX/
• http//www.db.ucsd.edu/Projects/MIX/
• Future work
• XMAS and DOM-VXD extensions
• Optimizing wrt. navigational complexity
• Better (quantitative) cost model

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Current MIX People

• Chaitan Baru, SDSC
• Amarnath Gupta, SDSC/UCSD
• Bertram Ludaescher, SDSC/UCSD
• Richard Marciano, SDSC
• Pratik Mukhopadhyay, UCSD
• Kevin Munroe, UCSD
• Yannis Papakonstantinou, UCSD
• Pavel Velikhov, UCSD
• Victor Vianu, UCSD
• Andreas Yannakopoulos, UCSD
• Ilya Zaslavsky, SDSC

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Translating result NCs into source NCs
root
root
...
...
tuple
tuple
tuple
tuple
t1
tname
tch
tn
t1
tname
tch
tn
te
c1
cm
...
c1
cm
c1
cm
...
...
root
tuple
f/d(tuple)rnamef
t0
tn
te
...
d/d(tuple)rchd
identity