Web Services Interfaces
Michalis Petropoulos
Alin Deutsch
Yannis Papakonstantinou
Vasilis Vassalos
Scott Mitchell
UNIVERSITY OF CALIFORNIA, SAN DIEGO
Microsoft Research, July 2003
Exporting DBMSs on the Web
Web
Service
Mediator
XML
DATABASE
APPLICATIONS
End-User
HTML
Forms &
Reports
– Web Services
(Function Signatures)
XML
• Integrating Web
Applications
XQuery
Web
Service
Web
Service
XML
View
XML
View
Source
Source
• Exporting Query
Capabilities on the Web
XML
Schema
– Use Web Services
– Export Query Capabilities
Themselves
• HTML Web Interfaces
(Forms & Reports)
DATABASE
SERVER
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
flights
airline +
name
flight *
from
to
day +
leg +
from
to
aircraft ?
• 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
Query Set Specification Language
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
name =‘Delta’
flight
from =‘JFK’
to =‘LAX’
day =‘MON’
leg
to =‘LAS’
flights/airline[name=‘Delta’]/flight[from=‘JFK’][to=‘LAX’][day=‘MON’][leg[to=‘LAS’]]
Query Set Specification Language
Query Set Specification
f1
f2
+ f3
? f4
f5
? f6
? f8
flights
flights
airline
airline
name=#1
name =#1
=‘Delta’
flight
flight
from =#2
from =#2
=‘JFK’
to =#3
to =#3
=‘LAX’
day =#4
day =#4
=‘MON’
leg
leg
to =#6
to =#6
=‘LAS’
flight
day =#7
Query Set Specification Language
Query Set Specification
f1
flights
airline +
name
flight *
from
to
day +
leg +
from
to
aircraft ?
flights
f2
airline
f2
name=#1
f2
f3
flight +
f3
f4
flights
airline
f1
from =#2
to =#3
f5
day =#4
f6
leg *
name=#1
flight
f4 ?
?
f7
from =#5 ?
f8
to =#6 ?
f9
aircraft =#7 ?
f3 +
f5
f4
from=#2
to =#3
f5
day =#4
f6 *
leg
f6
f7 ?
f8 ?
f7
from=#5
f8
to =#6
f9
aircraft =#7
• Similar to extended context-free grammars
f9 ?
Query Set Specification Language
Recursive XML Schemas
f1
f2
familyTree
familyTree
person
person
?
f3
name =#1
name =#1
?
f4
place=#2
place =#2
?
f5
spouse ?
spouse
?
f6
name =#3
?
f7
place=#4
?
f8
children ?
*
person
*
f2
children
person
person
spouse
name =#5
place =#6
Query Set Specification Language
Recursive XML Schemas
f1
f2
f1
familyTree
familyTree
f2
person
f3
name =#1 ?
f4
place=#2 ?
f5
spouse ?
f6
name =#3 ?
f7
place=#4 ?
f8
children ?
f2 *
• QSS of fixed size
person
f2
f3 ?
f4 ?
f3
name=#1
f4
place=#2
f5 ?
spouse
f5
f6 ?
f7 ?
f6
name=#3
f7
place=#4
f8
children
f2 *
f8 ?
Data Services
Input Message
View
XML Schema
Data
Source
Data
Service
WSDL
Agent
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
Input Message
TPX
View
XML Schema
WSDL
Input Message Type
Data
Source
Data
Service
QSSX
Agent
Output Message Type
XML Schema
Output Message
XML
• 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.
2.
3.
4.
Membership of a query in a data service
Subsumption of data services
Totality of a data service
Overlap of data services
• These problems (except 1) are undecidable for
context-free grammars
• QSS can be translated to an equivalent topdown nondeterministic unranked tree
automaton
• Problems become decidable
Future Work
Capability-Based Rewriting
Mediator
User Query
TPX
Rewriting
Processor
Candidate
Queries
Plan
Processor
Containing
Result
Remainder
Query
Execution
Engine
Data
Service
Data
Source
• Capability-based rewriting problem
– Partial rewritings
Query Result
XML
Data Services
Authoring Interface
Query Forms and Reports
Requirements
• Handle semistructureness
– Powerful query forms and reports
• Be declarative
– Separate logic from presentation
• Visual interface for the developer
– Programming should NOT be a requirement
Query Forms and Reports
Query Forms and Reports
QURSED Approach
End-User
Query
Form
Page
HTML
QURSED
Editor
QSS
XML
Schema
– Separation of content &
presentation
Report
Pages
QURSED
Engine
XQuery
XHTML
XQuery
Engine
• XML Schema-driven
• Declarative!
• 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
Developing Query Forms from
the XML Schema
Developing Reports from the
XML Schema
QURSED Editor
Building Query/Visual Association
Condition Fragment List
Data Path
Form Control
Predicate
QURSED Editor
Building Reports
Group By Mapping
Element Mapping
Elements
to Appear
on Report
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
End-User
Web
Site
– Forms as functions on
edges/links
Site
Generator
Presentation
Templates
SITE
GRAPH
Web Site
Content
and Structure
– Araneus
– Autoweb
Semistructured
Queries
(Mediated)
View
SCHEMA
SEMISTRUCTURED
DATA
• 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
?
Query Set Specification Language
Example Derivation
f1 ⇒
flights
airline
f2
⇒
f3 +
⇒
flights
airline
flight
name=#1
f4 ?
f5
flights
airline
name=#1
f6 *
flight
from=#2 to =#3 day =#4
f7 ?
⇒
flights
airline
name=#1
flight
from=#2 to =#3 day =#4
leg
to =#6
leg
f8 ?
f9 ?
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
Web Designer
End-User
WYSIWYG
XHTML
Editor
XHTML
Query Form
Page
BROWSER
Query
Form Page
Developer
Report
Pages
Query Set
Specification
APP SERVER
(Optional)
XHTML
Template
Report Page
(Optional)
Custom
Predicates
QURSED
Editor
Query Form
Page
Query/Visual
Association
XML
Schema
QURSED
Compiler
Deployment
Dynamic
Server Pages
QURSED
Run Time Engine
XQuery
Expressions
XML/XHTML
XQuery
Engine