Web Services Conversation Language Instructor: PINAR Yolum Presented by: ILIR Bojaxhiu (WSCL) December 28, 2005

Objectives..Why do we need WSCL? Where is WSCL used? What is WSCL? What does WSCL do? Elements of a WSCL Specification Extending WSCL..

..Why do we need WSCL? A typical Web service will require its operations to be invoked in a certain order to progress the interaction through to completion. Web services must expose computer-readable descriptions of how they should be used We need a standard way of describing dependencies between operations WSCL Defines WS Abstract Interface

Where is WSCL used?

What is WSCL? The first technology submitted to a standards body for describing the interactive behavioral aspects of a Web service (By HP, May 2001) The interaction between the consumer and provider of a service is achieved through XML document exchange WSCL is used to orchestrate the various message exchanges that occur at each stage of the conversation WSCL conversation definitions are themselves XML documents

What does WSCL do? Provides a means for: declaring the types of messages that are exchanged specifying the type of interaction that a message is used in (e.g. one-way, or bilateral) specifying the transition conditions that allow the conversation to progress from one interaction to the next.

Elements of a WSCL Specification WSCL Spec. has 4 main elements - Document types - Interactions - Transitions - Conversations

Document types Specify the types (schemas) of XML documents the service can accept and transmit in the course of a conversation. Types :InboundXMLDocument OutboundXMLDocument Ex:

Interactions Model the actions of the conversation as document exchanges between two participants Five types of interactions supported in WSCL: Send - service sends out an outbound document Receive - service receives an inbound document SendReceive - service sends out an outbound document and then expects to receive an inbound document in reply ReceiveSend - service receives an inbound document and then sends out an outbound document Empty - does not contain any documents exchanged, but is used only for modeling the start and end of a conversation

Interactions (Example) One-Way Interactions Two-Way Interactions

Transitions Used to specify: the ordering relationships between interactions specifies a source interaction a destination interaction a document type of the source interaction as an additional condition for the transition(optionally)

Transitions (Example) A conversation can proceed from one interaction to another as allowed by the permissible sequencing defined in the transition elements.

Conversations List all the interactions and transitions that make up the conversation Include: initialInteraction and finalInteraction name – the name of the conversation version (optional) – the version of the conversation. targetNamespace (optional) – the namespace of this conversation as it should be used when elements of this conversation are referenced in other XML documents. hrefSchema (optional) – the URL of the file containing this conversation definition. description (optional)

Conversations <Conversation name="StoreFrontServiceConversation" version="1.01“ xmlns=" initialInteraction="Start" finalInteraction="End" targetNamespace=" StoreFront101“ hrefSchema=" schema_files/StoreFront101.wscl" description="Conversation for a Store Front Service" > list of all the interactions list of all the transitions

Initial and Final Interactions Part of defining the possible ordering of interactions is the specification of the first and last interactions of a conversation. initialInteraction - references the ID of the first interaction to be executed in the conversation. finalInteraction - references the ID of the last interaction to be executed in the conversation. There might be more than one interaction with which the conversation can start or end.

initialInteraction Ex: Purchase Conversation Definition Login Purchase Shipping ValidLoginRS PurchaseAcceptRS InvalidLoginRS OutOfStockRS InvalidPaymentRS Start fnitialInteraction End Arrow = Transition Oval = Interaction

Extending WSCL.. The WSCL specification contains the smallest possible set of elements and attributes to describe conversations. Possible extensions: Defining document types that have non-XML content (e.g. binary attachments) Multi-party conversations with three or more participants or roles Expressing timeouts and other quality of service characteristics of individual interactions

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