Transcript Web Service Information Systems and Applications

Web Service Information
Systems and Applications
GGF16 Semantic Grid Workshop
Athens Greece
February 15 2006
Geoffrey Fox
Computer Science, Informatics, Physics
Pervasive Technology Laboratories
Indiana University Bloomington IN 47401
http://grids.ucs.indiana.edu/ptliupages/presentations/
[email protected]
http://www.infomall.org
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Different Metadata Systems
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There are many WS-* specifications addressing meta-data
defined broadly
• WS-MetadataExchange
• WS-Context
• ASAP
• WS-RF
• WBEM
• UDDI
• WS-GAF
• WS-ManagementCatalog
And many different implementations from (extended) UDDI
through MCAT of the Storage Research Broker
And of course representations including RDF and OWL
Further there is system metadata (such as UDDI for core
services) and metadata catalogs for each application domain
such as WFS (Web Feature Service) for GIS (Geographical
Information Systems)
They have different scope and different QoS trade-offs
• e.g. Distributed Hash Tables (Chord) to achieve scalability in large scale networks
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Different Trade-offs
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It has never been clear to me how a poor lonely service is meant
to know where to look up meta-data and if it is meant to be
thought up as a database (UDDI, WS-Context) or as the contents
of a message (WS-RF, WS-MetadataExchange)
We identified two very distinct QoS tradeoffs
1) Large scale relatively static metadata as in (UDDI) catalog of
all the world’s services
2) Small scale highly dynamic metadata as in dynamic workflows
for sensor integration and collaboration
• Fault-tolerance and ability to support dynamic changes with
few millisecond delay
• But only a modest number of involved services (up to 1000’s
in a session)
• Need Session NOT Service/Resource meta-data so don’t use
WS-RF
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XML Databases of Importance
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We choose a message based interface to a backend database
We have two pieces of technology with different trade-offs but
each could store any meta-data but with different QoS
• WS-Context designed for controlling a workflow
• (Extended) UDDI exemplified by semantic service discovery; can now be
Grimoires
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WFS provides general application specific XML data/meta-data
repository built on top of a hybrid system supported by UDDI
and WS-Context
These have different performance, scalability and data unit size
requirement
In our implementation, each is currently “just an
Oracle/MySQL” database front ended by filters that convert
between XML (GML for WFS) and object-relational Schema
• Example of Semantics (XML) versus representation (SQL)
difference
OGSA-DAI offers Grid interface to databases – we could use but
don’t as we only need to expose WFS and not MySQL to Grid
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WFS: Geographical Information System
compatible XML Metadata Services
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Extended UDDI XML Metadata Service (alternative
to OGC Web Registry Services) supports WFS GIS
Metadata Catalog (functional metadata), userdefined metadata ((name, value) pairs), up-to-date
service information (leasing), dynamically updated
registry entries.
Our approach enables advanced query capabilities
• geo-spatial and temporal queries ,
• metadata oriented queries,
• domain independent queries such as XPATH,
XQuery on metadata catalog.
http://www.opengrids.org/extendeduddi/index.html
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WMS uses WFS that uses data sources
<gml:featureMember>
<fault>
<name> Northridge2 </name>
<segment> Northridge2
</segment>
<author> Wald D. J.</author>
<gml:lineStringProperty>
<gml:LineString
srsName="null">
<gml:coordinates>
-118.72,34.243 118.591,34.176
</gml:coordinates>
</gml:LineString>
</gml:lineStringProperty>
</fault>
</gml:featureMember>
`
WMS
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Railroads
WFS Server
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River [a-d]
Bridge [1-5]
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SQL Query
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Interstate
Highways
Rivers
Bridges
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Electric Power and Natural Gas data from LANL
Interdependent Critical Infrastructure Simulations
WMS
Interface
Zoom-in
Zoom-out
FeatureInfo mode
Measure distance mode
Clear Distance
Drag and Drop mode
Refresh to initial map
Google maps
can be
integrated with
Web Feature
Service
Archives to
filter and
browse seismic
records.
Integrating
Archived Web
Feature Services
and Google Maps
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Context as Service Metadata
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We define all metadata (static, semi-static, dynamic)
relevant to a service as “Context”.
Context can be associated to a single service, a
session (service activity) or both.
Context can be independent of any interaction
 slowly varying, quasi-static context
 Ex: type or endpoint of a service, less likely to
change
Context can be generated as result of service
interactions
 dynamic, highly updated context
 information associated to an activity or session
 Ex: session-id, URI of the coordinator of a
workflow session
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Hybrid XML Metadata Services –>
WS-Context + extendedUDDI
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We combine functionalities of these two services: WSContext AND extendedUDDI in one hybrid service to
manage Context (service metadata).
• WS-Context controlling a workflow
• (Extended) UDDI supporting semantic service
discovery
This approach enables uniform query capabilities on
service metadata catalog.
http://www.opengrids.org/wscontext/index.html
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IS Client
WSDL
IS Client
WSDL
IS Client
WSDL
HTTP(S)
WS-Context Ver1.0
ws-context.wsdl
Optimized for
Performance
WSDL
Extended
WS-Context
Service
JDBC
DB
dynamic metadata
WSDL WSDL WSDL
Information Service
WSDL
WSDL
Optimized for
Scalability
UDDI Version 3.0 WSDL
Service Interface Descriptions
uddi_api_v3_portType.wsdl
WSDL
Extended
UDDI Registry
Service
JDBC
DB
interaction-independent
relatively static metadata11
Applications I – Workflow based Geographical
Information System (GIS) Grids
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CGL GIS Research focuses on open source software for
Grids to support scientific/visualization applications.
• some focus areas are earthquake prediction and simulating
energy interdependencies with GIS Grids.
• http://www.crisisgrid.org
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We use WS-Context complaint Information Services for
storing transitory metadata for distributed state
information.
We use extended UDDI Information Services for
providing search/store/access to geo-spatial domainspecific metadata catalogs
All data filters output data as though they were a WFS
so data filters and sensors interchangeable
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Typical use of Grid Messaging in NASA
Sensor Grid
Grid Eventing
Datamining Grid
WFS is Universal Interface
GIS Grid
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Workflow
Extended UDDI and WS-Context compliant Information Services handle with
both quasi-static, slowly varying and dynamic highly updated metadata. 14
Real Time GPS
and Google Maps
Subscribe to live GPS
station. Position data
from SOPAC is
combined with Google
map clients.
Select and zoom to
GPS station location,
click icons for more
information.
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Application – Context Store usage in
communication of mobile Web Services
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Handheld Flexible Representation (HHFR) is an open
source software for fast communication in mobile Web
Services. HHFR supports:
• streaming messages, separation of message contents and
usage of context store.
• http://www.opengrids.org/hhfr/index.html
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We use WS-Context service as context-store for
redundant message parts of the SOAP messages.
• redundant data is static XML fragments encoded in every
SOAP message
• Redundant metadata is stored as context associated to service
conversion in place
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The empirical results show that we gain 83% in
message size and on avg. 41% on transit time by using
WS-Context service.
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Optimizing Grid/Web Service Messaging
Performance
Context-Store
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HHFR Scheme
Representation
Headers
Stream Info.
Save Context
(setContents)
Retrieve Context
(getContents)
Negotiation Over SOAP
HHFR Endpoint
(Conventional)
Stream of Message
in Preferred Representation
HHFR Endpoint
(Mobile)
The performance and efficiency of Web Services can be greatly increased in conversational
and streaming message exchanges by removing the redundant parts of the SOAP message.
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Application – Context Store usage in multimedia
collaboration environment such as GlobalMMCS
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GlobalMMCS is audio/video conferencing system.
http://www.globalmmcs.org
WS-Context service is used as session metadata catalog for
describing audio/video streams in a session.
• stream metadata might have various descriptive information such as
starting and ending RTP packet numbers, what topic is the stream is
published, etc..
• metadata is stored associated with sessions
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WS-Context service provides search/store/access interface for
stream metadata as archival store.
• Queries support archived (find all relevant data in past) metadata
• Queries support session – metadata relations (find all metadata for a given
session)
• Session discovery (find a session with given properties)
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Clients query context store for information to be able to
replay/playback an audio/video stream during or after
conference session.
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e-Annotation
e - Annotation
Player
Player
Archived
Archieved
stream list
Stream List
Archived Stream
Archived stream
Player
player
Real time
Real
Time
stream list
Stream List
Annotated
Annotation
/WB
Stream
Player
player
Real time stream
player
e-Annotation
e -Annotation
Whiteboard
Whiteboard
Real Time
Player
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