1. This Presentation Courtesy of the
International SOA Symposium
October 7-8, 2008 Amsterdam Arena
www.soasymposium.com
info@soasymposium.com
Founding Sponsors
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RDF and SOA
David Booth, Ph.D. <dbooth@hp.com>
HP Software
SOA Symposium, Amsterdam, 8-Oct-2008
[Presented by Andrew Weaver, HP Software]
Latest version of these slides:
http://dbooth.org/2008/soas/slides.ppt
© 2008 Hewlett-Packard Development Company, L.P.
The information contained herein is subject to change without notice
1 October 2003 Copyright © 2006 HP corporate presentation. All rights reserved.

2. Outline
• PART 0: The problem
• PART 1: RDF: A lingua franca for information
exchange
• PART 2: Key Techniques for RDF in SOA
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PART 0
The problem
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3. Problem 1: Babelization
• Proliferation of data models (XML schemas, etc.)
• Parsing issues influence data models
• No consistent semantics
• Data chaos
Tower of Babel, Abel Grimmer (1570-1619)
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Problem 2: Integration complexity
• Multiple producers/consumers need to share data
• Tight coupling hampers independent versioning
Compliance Management Incident
Discovery Provisioning Management
Release Change
Management Management
Release Managers Operation Centers
Compliance
Managers
Source Control
Monitoring
Networking Engineers
Storage
Administrators
Unix System
Administrators
Windows System
Networking Ticketing
Administrators
Administrators
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4. Client/service versioning
• Need to version clients and services
independently
• Data models exchanged must evolve
• No such thing as the model:
− There are several, slightly different but related models
Client v3 Service v3
Client v2 Service v2
Client v1 Service v1
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What to do?
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5. PART 1
RDF: A lingua franca for
information exchange
in SOA
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What is RDF?
• Resource Description Framework
• Relational data model framework
• W3C standard >4 years
• Foundation of Semantic Web technology
• Language for making statements about things
• Used to express both:
− Ontologies (classes and relationships), and
− Instance data
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6. Key features of RDF
• Syntax independent (specifies model)
− Some existing serializations: RDF/XML, N3, Turtle
− Focus on semantics
• Consistent semantics
− Based on URIs
• Great for data integration problems
− Data "mashups"
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Why RDF for SOA?
1. Emphasis on semantics
− RDF is syntax independent
2. RDF is good at data integration
3. RDF helps bridge other formats/models
4. Looser coupling
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7. Why?
1. Emphasis on semantics
• RDF is syntax independent
• RDF specifies information model -- not
serialization
• Various serializations can be used
− RDF/XML, N3, Turtle, etc.
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Why?
2. Easier data integration
• New data models can be easily added
• Old and new data models co-exist in merged
model
• Relationships between the old and new models
are expressed explicitly
• Both old and new can be used simultaneously
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8. Why?
2. Easier data integration
• Blue App has model
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Why?
2. Easier data integration
• Red App has model
• Need to integrate Red & Blue models
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9. Why?
2. Easier data integration
• Step 1: Merge RDF
• Same nodes (URIs) join automatically
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Why?
2. Easier data integration
• Step 2: Add relationships and rules
• (Relationships are also RDF)
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10. Why?
2. Easier data integration
• Step 3: Define Green model
• (Making use of Red
& Blue models)
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Why?
2. Easier data integration
• What the Blue app sees:
− No difference!
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11. Why?
2. Easier data integration
• What the Red app sees
• No difference!
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Why?
3. RDF helps bridge other formats/models
• Producers and consumers may use different formats/models
• Rules can specify transformations
• Inference engine finds path to desired result model
A1
X
A2
A3
RDF B1
Y Model
Transform B2
C1
C2
Z Ontologies
Ontologies
& Ontologies
&Rules
&Rules
Rules
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12. Why?
4. Looser coupling
• Without breaking consumers:
− Ontologies can be mixed and extended
− Information can be added
• Producer & consumer can be versioned more
independently
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Example of looser coupling
• RedCust and GreenCust ontologies added
• Blue app is not affected
(Blue app)
Consumer Producer
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13. PART 2
Key Techniques for
RDF in SOA
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1. RDF message semantics
• Interface contract can specify RDF, regardless of
serialization
• RDF pins the semantics
RDF
Consumer Producer
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14. But Web services already use XML!
• XML is well known and used
• Legacy apps may require specific XML or other
formats that cannot be changed
• How can we gain the benefits of RDF message
semantics while still accommodating XML?
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Custom XML serializations of RDF
Recall: RDF is syntax independent
• Specifies info model -- not syntax!
• Can be serialized in any agreed-upon way
Therefore:
• Can view existing XML formats as custom
serialization of RDF!
How? GRDDL . . .
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15. What is GRDDL?
• Gleaning Resource Descriptions from Dialects of
Languages
• W3C standard
• Permits RDF to be "gleaned" from XML
• XML document or schema specifies GRDDL
transformation for that document (or type)
− Each XML document/type can use a different GRDDL
transformation
• GRDDL transformation produces RDF from XML
document
− Typically written in XSLT
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2. GRDDL transformations from XML to
RDF
Therefore:
• Same XML document can be consumed by:
− Legacy XML app
− RDF app
• App interface contract can specify RDF
− Serializations can vary
− Semantics are pinned by RDF
• Helps bridge XML and RDF worlds
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16. Bridging XML and RDF
Service
XML/other Normalize
to RDF
Core App
Client Processing
Serialize as
XML/other/RDF
• Input: Accept whatever formats are required
− Use GRDDL to transform XML to RDF
• Output: Serialize to whatever formats are required
− Generate XML/other directly (or even RDF!), or
− SPARQL query can generate specific view first
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3. REST-based SPARQL endpoints
HTTP
SPARQL
RDF
Consumer Producer
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17. REST-based SPARQL endpoints
• Why REST:
− HTTP is ubiquitous
− Simpler than SOAP-based Web services (WS*)
− Looser process coupling
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REST-based SPARQL endpoints
• What is SPARQL:
− Simple Protocol And RDF Query Language
− W3C standard
− Query language for RDF
− Modeled after SQL:
SELECT ...
WHERE ...
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18. REST-based SPARQL endpoints
• Why SPARQL:
− RDF gives looser data coupling
− Insulates consumers from internal model changes
• Inferencing can transforms data to consumer's desired model
− One endpoint supports multiple consumer needs
• Each consumer gets what it wants
− Simpler interface for consumers
• Uniform SPARQL interface instead of a different set of
parameters for each REST endpoint
• Takes the REST notion of "uniform interface" one step farther
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4. Aggregators
• Gets data from multiple sources
• Provides data to consumers
• Does model transformation, caching, etc.
• Conceptual component -- not necessarily a separate
service
A1
X
A2
A3
SPARQL
B1
Y Aggregator
B2
C1
C2
Z Ontologies
Ontologies
& Ontologies
&Rules
&Rules
Rules
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19. Conclusions
• Value of RDF in data integration is well proven
• RDF can bring looser coupling to SOA
• Key techniques:
1. RDF message semantics
2. REST-based SPARQL endpoints
3. GRDDL to bridge from XML to RDF
4. Aggregators
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More information
• RDF and SOA:
http://dbooth.org/2007/rdf-and-soa/rdf-and-soa-paper.htm
• RDF:
http://www.w3.org/TR/REC-rdf-syntax/
• SPARQL:
http://jena.sourceforge.net/ARQ/Tutorial/
• GRDDL:
http://www.w3.org/TR/grddl-primer/
38 October 8, 2008 HP Software (c) 2008 - SOA Symposium
19 October 2003 Copyright © 2006 HP corporate presentation. All rights reserved.

20. Outline
• PART 0: The problem
• PART 1: RDF: A lingua franca for information
exchange
• PART 2: Key Techniques for RDF in SOA
39 October 8, 2008 HP Software (c) 2008 - SOA Symposium
Questions?
© 2008 Hewlett-Packard Development Company, L.P.
The information contained herein is subject to change without notice
20 October 2003 Copyright © 2006 HP corporate presentation. All rights reserved.