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Composable XML Integration Grammars

Xibei Jia

x.jia@sms.ed.ac.uk

Laboratory for Foundations of Computer Science

Supervisor: Wenfei Fan

20 May 2004

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Schema-directed XML integration

extract relevant data from distributed, multiple XML repositories

construct an XML view conform to a predefined schema

XML3

XML1

XML view

XML2

middleware

schema

data exchange

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Composable XML Integration

A lightweight language: XML Integration Grammar (XIG)

XML

XIGmiddleware

XMLXML

XML

XIGmiddleware

XMLXML

XML

XIGmiddleware

XMLXML XML

XIGmiddleware

XMLXML

XML

XIGmiddleware

XMLXML

query

result

wwwwww www www

www

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Our middleware for composable schema-directed integration

XMLXMLXML

data sources

remoteXIG

XQueryengine

remoteXIG call

executionquery

scheduling

XQuery optimizer

querymerging

optimizerparsing

XIG XML document

cost statistics data call result

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XIG: XML Integration Grammar

XIG: a novel specification language– Is not another query/transformation language – Rely solely on DTDs and XQuery– Provide a systematic mechanism and design tool to ensure

DTD-conformance for XQuery– Can be defined using some specific XQuery fragment that

allows for more optimizations than full-fledged XQuery– Composable: local/remote XIGs can be treated as functions

returning XML trees and can be embedded

A systematic framework for schema-directed XML integration

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Example: car sale

db dealers, promotion

Syn(db) = <db> {Syn(dealers)} {Syn(promotion)} </db>

promotion sale *

Syn(promotion) = Vsale(X)

dealers dealer *

Inh(dealer) = for $Y in R/dl return $Y;

Syn(dealers) = <dealers> { Syn(dealer) } </dealers>

dealer name, address, cars

Inh(name) = let $p := Inh(dealer)/Uv

let $u := Inh(dealer)/U

let $v = $p:Vdealer($u)

return $v/dealer/name;

Syn(dealer) = <dealer> { Syn(name) } { Syn(address) } { Syn(cars) }

</dealer>

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Example: car sale

car car *

Inh(car) let $s := Vsale(X)

for $c in Inh(cars)/car

$c1 in $s/promotion/sale

where $c/make = $c1/make and $c/model =

$c1/model

return $c

Syn(cars) = <cars> { Syn(car) } </cars>

car make, model, price, inStock

Syn(car) = Inh(car)

name PCDATA /* similarly for address */

Syn(name) = Inh(name)/text();

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XIG-Evaluation Algorithms

Optimization techniques: nontrivial optimization problems

– recursion: capture recursive DTDs and recursive XIGs

– query scheduling: a cost-based algorithm for scheduling

local XML queries/XIGs and remote XIGs to maximize

parallelism

– query merging: merge certain queries processed at the

same source into a larger query to reduce communication

costs

– interaction between query merging and query scheduling:

have to be dealt with together, a greedy heuristic algorithm

– query dependency: XIGs support top-down, bottom-up and

sideway information passing (implicit)