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Navigation-Driven Evaluation of Virtual Mediated Views

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

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Navigation-Driven Evaluation of Virtual Mediated Views

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  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. XMAS View Definition MIXm Mediator XML View XML View XML View Wrapper Wrapper Data Source XML Data Source Data Source Mediator Architecture for Virtual XML Documents (DOM-VXD) Client Query Integrated XML View

  3. Integrated Virtual XML View XMAS View Definition Virtual XML View Virtual XML View Virtual XML View Wrapper Wrapper Data Source XML Data Source Data Source Mediator Architecture for Virtual XML Documents (DOM-VXD) Client Query MIXm Mediator

  4. answer book author Ullman title DB Systems dblp-pubs publication ... publication dblp … author name Ullman pubs publication … publication db-books@amazon book author Ullman title DB Systems book author … 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 < j) p1 d r r r p4 f d d

  11. Query Processing XMAS Query XMAS View Definition Translator Algebraic Plan for the View Algebraic Plan for the Query Composition (qov) Composed Algebraic Plan Rewriter/Optimizer Compile-time Optimized Plan Run-time: lazy VXD evaluation Plan Execution

  12. XMAS Queries (XML Matching And Structuring Language) CONSTRUCT <books> <book> $a1 $t <pubs> $p { $p } </pubs> </book> { $a1, $t} </books> WHERE <books.book> $a1 : <author /> $t : <title /> </> IN "amazon.com" AND <authors.author> $a2 : <author /> <pubs> $p : <pub/> </> </> IN "www...DBLP… " AND value( $a1) = value( $a2 )

  13. XMAS Algebra createElement”book”, $list -> $Res • Concat[$a1, $t,$eps]-> $list • createElement“pubs”,$ps->$eps • removeDuplicates[$a1, $t] • groupBy[$a1 ,$t],$p->$ps val($a1)=val($a2) getD$auth,”pubs.pub”->$p getD$book,”title”->$t getD$auth,”name”->$a2 getD$book,”author”->$a1 getDamazon,”books.book”->$book getDDBLP,”authors.author”->$auth

  14. XMAS Algebra • relational operators • + XML specific ones ( nest, unnest + pe’s) • works on trees of variable bindings createElementname,ch->e createListname,ch->e concatenate[l1…lk]->z groupBy[a1…gk],v->l getDescendentse,pe->ch getNamee->name assignf[u1…un],[v1…vn]->x mapf[u1…un],[v1…vn]->[x1…xn] …

  15. Natural measure: client vs. source navigationsnavigations Complexity XMAS Operators Bounded createElement, getName, concat,  getDescendents, groupBy, , , Browsable setdiff, orderBy Unbrowsable 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:

  16. materialize Browsable Unbrowsable Optimizing Using Navigational Complexity Potential for optimization of unbrowsable sub-parts:

  17. Granularity of Navigations Mismatch: Source granularity <=!=> DOM-VXD granularity (RDB: sets of tuples vs. individual table cells) => source should control result granularity => generic buffer component (above the wrapper) based on LXP (Lean XML Fragment Protocol)

  18. Holes 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

  19. 2400 homes Some Empirical Results: SelectionQueries

  20. Performance Evaluation: Construction Queries 328 homes x 122 schools

  21. 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

  22. 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

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

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