1. © 2006 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice RDF and SOA David Booth, Ph.D. 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

2. 21 June 2015 Outline PART 0: The problem PART 1: RDF: A lingua franca for information exchange PART 2: Key Techniques for RDF in SOA

3. 31 June 2015 PART 0 The problem

4. 41 June 2015 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)

5. 51 June 2015 Problem 2: Integration complexity Multiple producers/consumers need to share data Tight coupling hampers independent versioning Provisioning Discovery Change Management Compliance Management Incident Management Release Management Monitoring Ticketing Release Managers Unix System Administrators Networking Engineers Networking Administrators Compliance Managers Windows System Administrators Operation Centers Storage Administrators Source Control

6. 61 June 2015 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 v3Client v2Client v1 Service v3Service v2Service v1

7. 71 June 2015 What to do?

8. 81 June 2015 PART 1 RDF: A lingua franca for information exchange in SOA

9. 91 June 2015 What is RDF? "Resource Description Framework" Relational data model framework W3C standard >6 years Foundation of Semantic Web technology Language for making statements about things Used to express both: −Ontologies (classes and relationships), and −Instance data

10. 101 June 2015 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"

11. 111 June 2015 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

12. 121 June 2015 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.

13. 131 June 2015 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

14. 141 June 2015 Why? 2. Easier data integration Blue App has model

15. 151 June 2015 Why? 2. Easier data integration Red App has model Need to integrate Red & Blue models

16. 161 June 2015 Why? 2. Easier data integration Step 1: Merge RDF Same nodes (URIs) join automatically

17. 171 June 2015 Why? 2. Easier data integration Step 2: Add relationships and rules (Relationships are also RDF)

18. 181 June 2015 Why? 2. Easier data integration Step 3: Define Green model (Making use of Red & Blue models)

19. 191 June 2015 Why? 2. Easier data integration What the Blue app sees: −No difference!

20. 201 June 2015 Why? 2. Easier data integration What the Red app sees No difference!

21. 211 June 2015 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 RDF Model Transform A1 A2 A3 B1 B2 C1 C2 X Y Z Ontologies & Rules

22. 221 June 2015 Why? 4. Looser coupling Without breaking consumers: −Ontologies can be mixed and extended −Information can be added Producer & consumer can be versioned more independently

23. 231 June 2015 Example of looser coupling RedCust and GreenCust ontologies added Blue app is not affected (Blue app) ConsumerProducer

24. 241 June 2015 PART 2 Key Techniques for RDF in SOA

25. 251 June 2015 1. RDF message semantics Interface contract can specify RDF, regardless of serialization RDF pins the semantics Client Service RDF

26. 261 June 2015 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?

27. 271 June 2015 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...

28. 281 June 2015 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

29. 291 June 2015 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

30. 301 June 2015 Bridging XML and 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 Normalize to RDF Serialize as XML/other/RDF Service Core App Processing Client XML/other

31. 311 June 2015 3. REST-based SPARQL endpoints Consumer Producer SPARQL RDF HTTP

32. 321 June 2015 REST-based SPARQL endpoints Why REST: −HTTP is ubiquitous −Simpler than SOAP-based Web services (WS*) −Looser process coupling

33. 331 June 2015 REST-based SPARQL endpoints What is SPARQL: −W3C standard −Query language for RDF −Modeled after SQL: SELECT... WHERE...

34. 341 June 2015 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

35. 351 June 2015 4. Aggregation and Transformation Gets data from multiple sources Provides data to consumers Does model transformation, caching, etc. Conceptual component -- not necessarily a separate service Aggregation & Transformation A1 A2 A3 B1 B2 C1 C2 X Y Z Ontologies & Rules SPARQL

36. 361 June 2015 Conclusions Value of RDF in data integration is well proven RDF can bring looser coupling to SOA Key techniques: −1. RDF message semantics −2. GRDDL to bridge from XML to RDF −3. REST-based SPARQL endpoints −4. Aggregation and transformation

37. 371 June 2015 More information RDF and SOA: http://dbooth.org/2007/rdf-and-soa/rdf-and-soa-paper.htm http://dbooth.org/2007/rdf-and-soa/rdf-and-soa-paper.htm RDF: http://www.w3.org/TR/REC-rdf-syntax/ http://www.w3.org/TR/REC-rdf-syntax/ SPARQL: http://jena.sourceforge.net/ARQ/Tutorial/ http://jena.sourceforge.net/ARQ/Tutorial/ GRDDL: http://www.w3.org/TR/grddl-primer/ http://www.w3.org/TR/grddl-primer/

38. 381 June 2015 Outline PART 0: The problem PART 1: RDF: A lingua franca for information exchange PART 2: Key Techniques for RDF in SOA

39. © 2006 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice Questions?