Generic%20Interoperability%20Framework

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Generic Interoperability Framework

• Introducing a semantic-oriented middleware
  technology
• Sergey Melnik, Stanford University

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Motivation

• Long-term goal of information integration
• independence of protocols, languages, data models
  and formats
• dynamic discovery of component functionality
• universal interface

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Universal interface

• Evolvability
• free well-defined extension
• mixing, partial understanding
• Interface description
• Open, simple, efficient

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Basic framework

• Components exchange messages
• Every message
• uses generic representation
• has well-defined meaning
• Descriptions of all message parts are dynamically
  available

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Generic representation

• 1) Data
• 2) Languages
• 3) Protocols
• 4) Interface descriptions, schemata etc.
• directed labeled graphs (RDF)

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Example protocols / message
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Example serialization in XML

• ltrdfRDF xmlnsrdfhttp//www.w3.org/TR/WD-rdf-sy
  ntax
• xmlnsDLhttp//www-diglib.stanford.edu//Sear
  ch/Coregt
• ltDLSearch queryDarwin AND (contraption OR
  machine)/gt
• lt/rdfRDFgt

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Example languages
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Example data / metadata
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Example schema / ontology
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Evolvability Interoperability
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Message composition
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Message composition example
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Layered architecture
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Transport

• Primitive message exchange only (message contains
  application-specific protocol information!)
• Full-duplex communication channel
• Serialization in XML (part of RDF standard)
• Specifications for TCP/IP and HTTP

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Layers API

• interface Layer
• Model dispatch(in Model m, in Layer from)
• void connect(in String channel, in Layer l)
• Generic dispatch
• Model provides graph manipulation API

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Example layers (1)
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Connecting layers (1)

• Layer l new LibraryLayer()
• Layer t new TransportLayer()
• l.connect( transport, t )
• t.connect( dispatch, l )

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Example layers (2)
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Connecting layers (2)

• Layer l new LibraryLayer()
• Layer t new TransportLayer()
• Layer e new ECommerceLayer()
• l.connect( transport, e )
• t.connect( dispatch, e )
• e.connect( service, l )
• e.connect( transport, t )

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Unknown message
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Connecting layers (3)
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Connecting layers summary

• no changes in Library components
• universal E-commerce Layer
• Can we do the same using distributed objects
  (CORBA)?
• Dynamic Invocation and Skeleton Interface
  (DII/DSI) only!
• Limitations interface descriptions, evolvability

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Integration

• Canonical wrappers
• preserve semantics of sources
• no additional functions
• no common models or languages
• Mediators
• perform translation of protocols, languages and
  data

(simple!)
(? stateful graph transformation!)
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Integration example (1)

• Source 1
• wind sensors
• delivers list of vectors
• Vector (x1,y1,x2,y2)

• Source 2
• interpolation based on energy conservation
• computes map
• 1 hour time to answer queries
• Vector (x,y,?,l)

• Mediator
• real-time wind conditions
• http//sfports.wr.usgs.gov/wind/
• every hour
• fetches sensor info
• translates vectors
• asks Source 2
• forwards requests
• Vector (x,y,?x,?y)

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Integration example (2)
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Current status

• Java libraries
• RDF parsing/serialization, model manipulation
• schema evaluation subClassOf, subPropertyOf,
  validation
• multithreaded TCP/IP, HTTP delivery
• small footprint lt 90K !
• Schemas (ontologies)
• Core Communication, Search, Load Balancing, State
  Maintenance
• http//www-diglib.stanford.edu/diglib/ginf/

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Conclusion

• Middleware for application development and
  integration
• Ontologies of protocols, languages and data
• Supports all of the semantics of components (not
  only querying!)

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Future work

• Modeling of advanced services
• rights management, payment etc.
• Sophisticated schema approaches
• declarative, Turing-complete, etc.
• On-demand layers, automatic mediation