Transcript Information Services for Dynamically Assembled Semantic Grids Mehmet S. Aktas, Geoffrey C. Fox, Marlon Pierce Community Grids Laboratory, INDIANA UNIVERSITY www.opengrids.org The First International Conference on.

Information Services for
Dynamically Assembled
Semantic Grids
Mehmet S. Aktas, Geoffrey C. Fox, Marlon Pierce
Community Grids Laboratory, INDIANA UNIVERSITY
www.opengrids.org
The First International Conference on Semantics, Knowledge
and Grid – SKG 2005, Beijing, China
Context as Service Metadata


Context is metadata associated to both services and
their activities
Context can be
• independent of any interaction

slowly varying, quasi-static context
• generated as result of interaction

dynamic context
• Example: information associated to an activity or session

Gaggles: Collection of Services that
• are set of actively collaborating managed services for a
particular common goal
• generate events as result of interactions
• are very small part of the whole Grid
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Motivating Scenario: Pattern
Informatics (PI) in a Grid Environment

PI in a Grid environment:
• Hotspot forecasts are made using publicly available
seismic records.
 Southern California Earthquake Data Center
 Advanced National Seismic System (ANSS) catalogs
• Code location is unimportant, can be a service through
remote execution
• Results need to be visualized, stored, shared, modified
• Grid/Web Services can provide these capabilities
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PI GIS GRID
WFS
WMS
1
WMS
Client
2
5,6,7
4
3
http://..../..../..txt
HP Search
Data Filter
PI Code
Data Filter
http://..../..../tmp.xml

Information
Requirements in
PI GIS Grid
Support for slowly varying, quasi-static metadata
• How do we support both prescriptive and descriptive metadata?
• How do we enforce up-to-date information in registries?

Support for dynamic session related metadata
• How do we manage dynamic workflows?
• How do we enable correlation of service activities?
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Context Information Services
Motivations


Need to provide information describing services independent
of their interactions.
• generic and domain specific characteristics of services
Need to manage all information associated with services for;
• correlating activities of widely distributed services
• enabling uniform query capabilities to both conversationbased or monolog context information

“Give me list of services satisfying C:{a,b,c..} QoS requirements
and participating S:{x,y,z..} sessions”
• management of events especially in multimedia
collaboration
• providing information to enable
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session failure recovery capabilities
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Problem Statement
What is a novel process of building
Information Services for both dynamic,
session related and slowly varying, static
context of widely distributed services
in Gaggles?
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What is WS-Context?


Repository of Context Information
Allows for
• Sharing Context info: metadata related to a particular
transaction in multiple Web Service interactions
• Sharing data: data in multiple Web service interactions
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
Nicely put, its a Distributed Variation of Shared
Memory
Context Information dependent on the type of activity

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Identify a transaction coordinator
Recovery information in event of a failure
Sharing info between participants (Security tokens,
certificates, transaction IDs…)
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Architectural Design Requirements

Uniformity
• need consistent interface to both static and dynamic context

Interoperability
• need to leverage existing WS standards (UDDI, WSContext) for service discovery and communication

Persistence
• need to provide high availability of information

Dynamism
• need to handle metadata based on changing user demands

Performance
• need to support dynamic changes with min. delay
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The Architecture of Context Information Service
Extended
UDDI Registry
Service
WSDL
HTTP
WSDL
Database
Access
JDBC
Querying
Storage
Expeditor
and
Sequencer
Publishing
WSDL
HTTP(S)
WSDL
Client
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WSDL
Client
WSDL
Client
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NB
Node
Fault Tolerant High Performance
Information Services (FTHPIS)

Performance, compatibility, uniform interface
• caching

Expeditor Module using Tuple Spaces paradigm
• web service based programming interface, UDDI & WSContext
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Querying and Publishing Modules
From single point of failure to distributed system:
fault tolerance
• dynamic replication

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Access Module
Storage Module
• multi-publisher multicasting messaging
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NaradaBrokering (www.naradabrokering.org)
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Distributed Dynamic Context Management
Computer Boundaries
Extended
UDDI Registry
Service
Gaggle Boundaries
WSDL
HTTP(S)
WSDL
Database
Access
Querying
and
Publishing
JDBC
Expeditor
Storage
NB
Node
Sequencer
WSDL
HTTP(S)
WSDL
Client
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NB plays role is for fast and
reliable multi-publisher, multicast
messaging among peer IS Services
0
Extended
UDDI
WFS
2
WMS
1
WMS
Client
5,11
3
5,6: WMS starts a session, invokes HPSearch to
run workflow script for PI Code with a session id
4
http://..../..../..txt
7,8,9
6
HP Search
10
7,8,9: HPSearch runs the workflow script and
generates output file in GML format (& PDF
Format) as result
Data Filter
10: HPSearch writes the URI of the of the output
file into Context
PI Code
11: WMS polls the information from Context
Service
Data Filter
12: WMS retrieves the generated output file by
workflow script and generates a map
http://..../..../x.gml
Context
Information Service
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://www.w3...">
<soap:Header
encodingStyle=“URL" mustUnderstand="true">
<context
xsd:type="ContextType"timeout=“100">
<context
xmlns=“ctxt schema“ timeout="100">
<context-service>http://.../HPSearch</
context-service>
<context
xsd:type="ContextType"timeout=“100">
<context-id>http..</context-id>
<context
xsd:type="ContextType"timeout=“100">
<parent-context>http://../abcdef:012345<parent-context/>
<context-service>http://.../WMS</
context-service>
<context
xsd:type="ContextType"timeout=“100">
<context-service>
http..
</context-service>
<context-id>http://../abcdef:012345<context-id/>
<content>
shared
data
for
HPSearch
activity
</content>
activity
<activity-list
mustUnderstand="true"
<context-service>http://.../HPSearch</
context<context-manager>
http..
</context-service>
<context-service>http://.../HPSearch</
context<activity-list
mustUnderstand="true"
mustPropagate="true">
<context
xsd:type="ContextType"timeout=“100">
The Pattern
Informatics
GIS-SOA
based
workflow
application
service>
mustPropagate="true">
session
<activity-list
service>
shared
<service>http://.../DataFilter1</service>
<context-service>http://.../HPSearch</
contextuser state
profile
<parent-context>http://../abcdef:012345<parentmustUnderstand="true"
mustPropagate="true">
<service>http://.../WMS</service>
service>
<service>http://.../PICode</service>
context/>
service
<p-service>http://../WMS</p-service>
SOAP
header
<service>http://.../HPSearch</service>
<content>http://danube.ucs.indiana.edu:8080\x.xml</c
<content>
HPSearch
associated additional
<service>http://.../DataFilter2</service>
profile information
related WMSdata
associated
<p-service>http://../HPSearch</p-service>
ontent>
</content>
generated
during execution of workflow. </content>
</activity-list>
</activity-list>
</activity-list>
for Context
</context>
</context>
</context>
</context>
</context>
</soap:Header>
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System Status - I

Extended UDDI Metadata Service
• OGC (Open Geographic Information Systems (GIS) Consortium)
specific service registry, up-to-date registry entries, metadata oriented
query capabilities and XPATH query capabilities..
• Status: 100 % completed. www.opengrids.org/extendeduddi
• Application domains: PI GIS Grid (UC at Davis), IEISS GIS Grid
(LANL)

WS-Context Complaint Metadata Services
• WS-Context compatibility, support for shared dynamic context
• Status: 100 % completed. www.opengrids.org/wscontext
• Application domains: PI GIS Grid (UC at Davis), IEISS GIS Grid
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System Status - II

Unified UDDI & WS-Context Metadata Services
• Both WS-Context and UDDI compatibility, uniform
programming interface to dynamic & static metadata,
caching (high performance), support for session-failure
recovery capabilities
• www.opengrids.org/wscontext
• Application domains: PI GIS Grid (UC at Davis), IEISS
GIS Grid, Global MMCS project
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Conclusions & Future Work


There may be following gaps in Semantic/Traditional Grid
Information Services.
• need for management of widely distributed, shared
session-related dynamic metadata
• need for enabling session failure recovery
• need for uniform search interface to both interaction
independent and conversation-based context
We introduce a novel architecture addressing these gaps by
taking into account;
• efficient metadata access and storage, decentralized fault tolerant
storage capability, uniform interface to context, minimum response
latency

We plan on investigating research issues related with fault
tolerance and consistency as future work. We also want to
evaluate the system as whole through extensive performance
tests.
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Location of information and software for
dependent Grid Projects

htpp://www.naradabrokering.org provides Web service
(and JMS) compliant distributed publish-subscribe
messaging (software overlay network)

http://www.crisisgrid.org is an OGC (open geospatial
consortium) Geographical Information System (GIS)
compliant GIS and Sensor Grid.

http://www.opengrids.org has WS-Context, Extended
UDDI etc.
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