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Asynchronous Linking in a Service—Oriented Architecture (“Stuff Happens”). Sanjay Vivek, Kenneth K. Tso, Mark K. Thompson, David C. De Roure Department of Electronics and Computer Science, University of Southampton UK. Position.

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asynchronous linking in a service oriented architecture stuff happens

Asynchronous Linking in a Service—Oriented Architecture(“Stuff Happens”)

Sanjay Vivek, Kenneth K. Tso, Mark K. Thompson, David C. De Roure

Department of Electronics and Computer Science, University of Southampton UK

position
Position
  • Service—Oriented Architectures (SOA) decouple components in space
  • Message—Oriented Middlewares (MOM) decouple components in time
  • This double decoupling is useful…
motivation
Motivation
  • Threefold motivation for asynchronicity
    • The ad hoc world where you walk into the room and stuff happens
    • The poor-performing-proxy world where the time-boundedness of link processing intrudes
    • The live-action, live-media worlds where the comms model is notification-based
position1
Position
  • Service—Oriented Architectures (SOA) decouple components in space
  • Message—Oriented Middlewares (MOM) decouple components in time
  • This double decoupling is useful for:

- mobile; lightweight; pervasive OHSes

- existing systems where synchronicity hurts

- linking from streamed media

overview
Overview
  • Service–Oriented Architectures
  • Asynchronous Interaction
  • Example with MQe™ and Auld Linky
  • Thoughts
service oriented architectures
Service—Oriented Architectures
  • SOA enable service components residing on a network to be published, discovered, and invoked by each other
  • Enables seamless interop between distributed components
  • Typically 3 components:
    • Service Provider
    • Service Broker
    • Service Requester
  • With 3 functions:
    • Find
    • Bind
    • Interact
web services example stack
Web Services Example Stack
  • Define interface to service components (e.g. Link service interface)
  • Publish service description in repository
  • Interact with other services to form complex applications

Workflow (WSFL)

Discovery (UDDI)

Description (WSDL)

Packaging (SOAP,XML)

Transport (HTTP, Jabber)

Network (TCP/IP)

asynchronous interaction
Asynchronous Interaction
  • Transaction-based fire-and-forget messaging
  • Queues of messages (function calls) directed towards services
  • Example: IBM’s MQSeries Everyplace (MQe)
    • Assured once-only delivery
    • Messages queued and routed toward end-points
    • Contextual triggers for additional functionality
    • Lightweight in speed and size
example using mqe and auld linky
N

Auld Linky

linkbases

Example using MQe™ and Auld Linky

before

HTTP

DLS

HTTP

HTTP

example using mqe and auld linky1
Example using MQe™ and Auld Linky
  • Ported Auld Linky’s HTTP interface for Linkbase query/update to a Web Service
  • Wrapped service with an MQe Custom Queue
  • HTTP Proxy-based DLS interacted with Linky using HTTP; now issues SOAP calls which are transported through MQe queues
example using mqe and auld linky2
N

Auld Linky’

queues

queues

linkbases

Example using MQe™ and Auld Linky

after

HTTP

DLS’

SOAP

HTTP

MQe QM

MQe QM

SOAP/MQe

SOAP/HTTP

issues with the dls mqe linky example
Issues with the DLS-MQe-Linky Example
  • Latency and QoP control
    • Additional overhead in the path from query source to query target
    • Application context can determine prioritisation of link resolution events
  • Modality of link resolution has shifted
    • Non-availability of clients results in requests/responses being “buffered”, but for how long?
  • Concurrency; Resilience; Query-routing…
thoughts
Thoughts
  • Is such decoupling good for the soul?
    • Asynchronicity; Dislocation
  • Different Link service interaction
    • Notifications and the “Null Query”
  • Other OHS layers and functions, beyond Links
    • Linking is fun, but executable structures (with continuations) could be more-so(!)
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