Incorporating Preferences into Web Service Conversations MobEA III WWW 2005

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Incorporating Preferences into Web Service
ConversationsMobEA III _at_ WWW 2005

• Jonghun Park
• jonghun_at_snu.ac.kr
• Seoul National University
• Co-Authors Wan Lee (SNU), Kangchan Lee (ETRI)

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Presentation outline

• Background, Motivation, Objectives
• Proposed Preference Model
• WS-CPP Structure
• Run-time Behavior
• Conclusions

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Background

• Web services A software application identified
  by a URI, whose interfaces and bindings are
  capable of being defined, described, and
  discovered as XML artifactsA Web service
  supports direct interactions with other software
  agents using XML-based messages exchanged via
  Internet-based protocols (W3C)
• Web based
• Big thrust from major IT vendors
• Interoperability supported by international
  standards

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Background (cont.)
Web Services Stack
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Background (cont.)

• Web services choreography
• aims at the coordination of interactions between
  distributed parties, which define web services to
  expose their externally accessible operations
• WS-CDL (Web Services Choreography Description
  Language) ver. 1.0
• W3Cs Web Services Choreography WG
• An XML-based language that describes P2P
  collaborations of WS participants through
  defining, from a global viewpoint, their common
  and complementary observable behavior, where
  ordered message exchanges result in accomplishing
  a common goal
• Other related work on the choreography
• WSCL HPs member submission to W3C
• Abstract WS-BPEL from OASIS

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Motivation

• WSs have been perceived as a means for e-Business
  automation and integration
• Now emerging as a platform for ubiquitous
  computing
• Web services are increasingly embedded into
  devices
• A device can automatically discover and
  inter-operate with other devices, establishing
  pervasive P2P network connectivity of computers
  of all form factors and wireless devices
• Interoperability problem is the crux of
  ubiquitous computing
• Some ongoing work
• UPnP 2.0
• Microsofts invisible computing
• NETCONF
• Samsungs iPC

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Motivation (cont.)

• Need for defining and deploying a choreography
  between a WS provider and a mobile client
• A mobile device may engage in a conversation with
  a service provider
• WS-CDL can be used to provide the rules of
  engagement
• Difficulties during the conversation
• Connection may be lost
• Mobile device may move into out-of-service area
• User may not be always attendant
• Problematic particularly for long-running
  conversation and conversation involving user
  interactions
• Performing mere step by step execution of a
  choreography specification may produce
  unsatisfactory performance results

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Objectives

• A framework through which mobile web service
  clients can express their preferences on how
  conversation should take place while being able
  to adhering to a choreography
• WS-CPP Web Services Conversation Preference
  Profile
• allows some of the activities defined in WS-CDL
  to be selectively skipped
• provides an effective means to flexibly minimize
  the of messages exchanged
• enables the preferences to be delivered to and
  interpreted by service providers
• Related work
• CC/PP
• considers the static web resources
• concerns with the adaptation of content presented
  to the devices

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Proposed preference model

• WS-CPP allows conversation preferences to be
  associated with some of the interactions defined
  in WS-CDL so that the specified interactions are
  not required during actual conversations
• Activity notation in WS-CDL
• The lowest level component in WS-CDL
• consists of basic activity, ordering structure,
  work unit notation
• Basic activity
• interaction, assign, perform, silent action, no
  action, finalize
• Ordering structure
• sequence, parallel, choice

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Example activity notations interaction
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Example activity notations choice
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WS-CPP structure

• preference
• the top level element of a WS-CPP document
• may contain 0 or more interactionSkip,
  choicePriority, and orderPriority
• interactionSkip
• represents a preference on the exchange element
  within an interaction activity in the WS-CDL
• indicates that a message expected to be delivered
  to a receiver will not be actually sent

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WS-CPP structure

• choicePriority
• allows the selection to be pre-specified when the
  client is required to make a decision among the
  available choices

• orderPriority
• specifies the clients execution ordering
  priority among the activities that can be enabled
  in parallel

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Run-time behavior

• Assume that a WS-CDL document is publicly
  available from a web service provider
• A developer writes a WS-CPP aware client
  application of which the interaction behavior
  conforms to the requirements specified in the
  providers WS-CDL
• A WS-CPP document is defined by a user agent
• The WS-CPP document is transmitted to the service
  provider when an actual conversation starts
• After the service provider has received the
  WS-CPP, it will refer to the preference
  specifications throughout the conversation

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Proposed run-time architecture
SOAP messages
SOAP router
WS-CDL engine
WS-CPP processor
Underlying application objects
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Example

• Example scenario
• A mobile device is within the range of wireless
  LAN which provides 2 types of on-demand
  multimedia streaming services regular vs. premium

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Example (cont.)
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Example (cont.)

• Example preferences
• P1 The client wants to skip the interaction for
  sending configuration data by providing them in
  the WS-CPP document.
• P2 The client prefers not to receive an ACK
  message for the configuration data transmission.
• P3 The client prefers the premium service to the
  regular service

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Example (cont.)
P1
P2
P3
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Conclusion

• We proposed an overlay preferencing mechanism
  that ultimately alleviates additional real time
  messaging requirements during web services based
  interactions
• The proposed WS-CPP can enhance the performance
  of mobile web services applications while
  supporting flexibility in web services
  conversation
• Current ongoing work
• extends the current profile to support additional
  WS-CDL features exceptions and loops
• develops a protocol for delivering WS-CPP
  specifications