web services interfaces

Web Services Interfaces

Michalis PetropoulosAlin Deutsch

Yannis PapakonstantinouVasilis VassalosScott Mitchell

UNIVERSITY OF CALIFORNIA, SAN DIEGO

Microsoft Research, July 2003

Exporting DBMSs on the Web

SourceDATABASE

SERVER

Source

XQuery

XML XML

XMLView

XMLSchema

XMLView

• Exporting Query Capabilities on the Web– Web Services

(Function Signatures)

• Integrating Web Applications– Use Web Services – Export Query Capabilities

Themselves

• HTML Web Interfaces(Forms & Reports)

WebService

WebService

Mediator

WebService End-User

HTMLForms &Reports

DATABASEAPPLICATIONS

Overview

• Query Set Specification Language (QSSL)– Describes Parameterized Tree Pattern (TP) Queries

• Data Services– Web Services for Query Capabilities

• Forms & Reports for Semistructured Data– The QURSED system

• Authoring Interfaces

Motivation for QSSL

• Web Services published as function signatures:– Fixed number of input and output parameters– Do not capture the functionality of databases– Large number of web services needed

– One function signature for every parameterized query

– Do not capture the semantic connections the available functions have with each other and with the underlying databases

• JDBC Interfaces– All possible queries– Difficult to export schema information

Query Set Specification Language

Goals • Any combination of the following conditions on:– the name of the airline company– the origin and destination of one or

more flights (optional)– a day of the week– the origin of zero or more legs

(optional)– the destination of zero or more legs

(optional)– the aircraft used for zero or more

legs (optional)

• The queries may return “airline”or “flight” elements

flights

airline

flight

name

from

to

day

leg

aircraft

to

from

+

*

+

?

+


Query Language

• Tree Pattern Queries:– Acyclic XPath expressions consisting

of:– node tests– child axis ‘/’– descendant axis ‘//’– predicates ‘[]’

– Widely used in current applications– Building blocks of XQuery– Excellent visual paradigm for GUIs

flights

airline

flight

name =‘Delta’

from

to =‘LAX’=‘JFK’

day =‘MON’leg

to =‘LAS’

flights/airline[name=‘Delta’]/flight[from=‘JFK’][to=‘LAX’][day=‘MON’][leg[to=‘LAS’]]


Query Set Specification

f8

f6

f5

f4

f3

f2

f1flights

airline

flight

name=#1

from

to =#3=#2

day =#4leg

to =#6

?

?

?

flights

airline

flight

name

day

leg

from

to

to

=‘Delta’

=‘LAX’=‘JFK’

=‘MON’

=‘LAS’

=‘Delta’

=‘LAX’=‘JFK’

=‘MON’

=‘LAS’

=#1

=#3=#2

=#4

=#6flight

day =#7

+


Query Set Specificationflightsf1

flights

airline

flight

name=#1

from

to =#3

=#2

day =#4

leg

aircraft

to

from

=#6

=#5

=#7

+

?

*?

??

airline

f3f2 +f1flights

airline

flight

name

from

to

day

leg

aircraft

to

from

+

*

+

?

+

name=#1f2f2f3 flight

f6f4 f5? *f3

f4 from=#2f4to =#3

f5day =#4f5

f6f6 leg

f9f7 f8 ?? ?f7

f8from=#5f7

f9to =#6f8

aircraft=#7f9

• Similar to extended context-free grammars


Recursive XML Schemas

familyTree

person

spouse

name

name

children?

?place

place

person *

familyTree

person

name

place

=#1=#2

spouse

name

place

=#5=#6

f8

f7

f6

f5

f4

f3

f2

f1

?????

familyTree

person

spouse

name

name

children

place

place

=#1=#2

=#3=#4

?f2*

children

person

spouse

person


Recursive XML SchemasfamilyTreefamilyTree

person

spouse

name

name

children

f2

place

place

=#1

=#2

=#3

=#4

?

*

f1 f1f2f2

f2 person

f5f3 f4 ?? ??f3

?f4name=#1f3

f5 ?place=#2f4

?f6f5 spouse

f8f6 f7 ?? ??f7

f8name=#3f6

place=#4f7

childrenf8f2 *

• QSS of fixed size

Data Services

Input Message

Agent

ViewXML Schema

DataService

DataSource

WSDL

Output Message

• Data Service = WSDL + QSS• A QSS deployed as a web service• Exports the XML Schema of an XML view• Connects the WSDL calls with the underlying

database• Receives queries that are encoded by QSS• Explicit relationship between input and output

Data Services

WSDLInput Message Type

Output Message Type

Output Message

Input Message

QSSX

XML Schema

XML

TPX

DataService

ViewXML Schema

DataSource

Agent

• QSS is translated to XML Schema (QSSX)• TP queries that are encoded as XML (TPX)• Query result is described by an XML Schema

Data Services

Reasoning

1. Membership of a query in a data service2. Subsumption of data services3. Totality of a data service4. Overlap of data services

• These problems (except 1) are undecidable for context-free grammars

• QSS can be translated to an equivalent top-down nondeterministic unranked tree automaton

• Problems become decidable

Future Work

Capability-Based Rewriting

RewritingProcessor

PlanProcessor

CandidateQueries

MediatorContaining

Result

DataSource

• Capability-based rewriting problem– Partial rewritings

Query ResultUser Query

XMLTPXExecution

EngineRemainderQuery

DataService

Data Services

Authoring Interface

Query Forms and Reports

• Handle semistructureness– Powerful query forms and reports

• Be declarative– Separate logic from presentation

• Visual interface for the developer– Programming should NOT be a requirement

Requirements


• XML Schema-driven• Declarative!

– Separation of content & presentation

• Editor– Visual actions to declarative

specifications– Automatic construction of

report pages• Query Set Specification (QSS)

– Large set of parameterized queries

– Compact representation• Engine

– Automatic query formulation– Direct result construction

QURSED Approach

QURSEDEngine

XQueryEngine

XQuery

QueryFormPage

ReportPages

End-User

XHTML

QSS

QURSEDEditor

XMLSchema

HTML

Developing Query Forms from the XML Schema

Developing Reports from the XML Schema

QURSED Editor

Building Query/Visual Association

Condition Fragment List

Predicate

Data Path

Form Control

QURSED Editor

Building Reports

Elementsto Appearon Report

Element Mapping

Group By Mapping

More Features

• Structural disjunction• Dependencies• Sort-by options• Template-driven construction of report pages• Report customization• Dynamic projection• Online demo:

http://www.db.ucsd.edu/qursed/



Related work

• Data intensive Web site generators– Strudel

– Forms as functions on edges/links

– Araneus– Autoweb

SEMISTRUCTUREDDATA

(Mediated)View

End-User

Presentation Templates

SiteGenerator

WebSite

SITEGRAPH Web Site

Contentand Structure

SemistructuredQueries

SCHEMA

• Declarative• Separation of content,

structure and presentation

Related work

• Web-based Form and Report Generators– Macromedia Ultradev, Coldfusion, Microsoft Visual InterDev– Excellent for flat uniform relational tables– Visual query formulation paradigm allows the specification of

projections, sort-bys, simple conditions– However, the development of form and report pages for

semistructured data requires substantial programming effort

• Visual Querying Interfaces– EquiX, BBQ, VQBD, Lorel’s DataGuide-driven GUI, PESTO– Excellent visual paradigm for the formulation of fairly

complex queries – The goal is the development of a query or a query template– User needs to be familiar with database models and schemas

Questions and Answers

?


Example Derivation

flights

airline

f3f2 +

f1

flight

f6f4 f5

airline

? *

flights

from=#2 to =#3 day =#4leg

flight

airline

f7 f8 ??

flights⇒ ⇒ ⇒

name=#1 name=#1

f9 ?

to =#6

from=#2 to =#3 day =#4

flight

airline

flights⇒

name=#1

leg

Related Work

Capability-Based Rewriting

• Capabilities described as binding patterns– Adornments on view attributes– Negative approach

• Expansions of Datalog programs– Recursive programs Infinite queries– Positive approach

• Capability-based rewriting problem– Total rewritings only

QURSED System Architecture

QURSEDRun Time Engine

QURSEDCompiler

XQueryEngine

QURSEDEditor

(Optional)Custom

Predicates

Query FormPage

XQueryExpressions XML/XHTML

QueryForm Page

ReportPages

APP SERVER

BROWSER

XHTMLQuery Form

Page

(Optional)XHTML

TemplateReport Page

Query SetSpecification

Query/VisualAssociation

DynamicServer Pages

WYSIWYGXHTMLEditor

Deployment

XMLSchema

Developer

Web Designer

End-User

web services interfaces

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