The Web Service Choreography Interface (WSCI) 1.0 specification has been submitted to W3C by member companies BEA Systems, BPMI.org, Commerce One, Fujitsu Limited, Intalio, IONA, Oracle Corporation, SAP AG, SeeBeyond Technology Corporation, and Sun Microsystems. Initially released in June 2002 and now published as a W3C 'Note', the royalty-free WSCI specification provides an "XML-based interface definition language that describes the flow of messages exchanged by a Web service participating in choreographed interactions with other services. WSCI describes the dynamic interface of the Web service participating in a given message exchange by means of reusing the operations defined for a static interface. This is expressed in terms of temporal and logical dependencies among the exchanged messages, featuring sequencing rules, correlation, exception handling, and transactions. WSCI also describes the collective message exchange among interacting Web services, thus providing a global, message-oriented view of the interactions. WSCI works in conjunction with the Web Service Description Language (WSDL), the basis for the W3C Web Services Description Working Group. It can also work with another service definition language that exhibits the same characteristics as WSDL." The specification is being brought to the attention of relevant W3C working groups, including the Web Services Architecture Working Group, the Web Services Description Working Group, and the Web Ontology Working Group.

From the W3C staff comment:

The Web Service Choreography Interface Language aims to describe the complete set of interactions between Web Services using an XML-based language.

An interaction, or choreography, between two Web Services -- if the Web Service Client is also seen as a Web Service -- is divided into a set of processes and sub-processes, containing themselves a set of operations executed to complete the process. Processes and operations can happen in sequence or in parallel. WSCI contains mechanims to define; the list is not exhaustive: [1] the relations and correlation between the operations; [2] the relations, or the composition, between the processes; [3] a concept of atomic or open transaction, i.e., if an activity must be seen as a single unit of work or not; [4] and a way to connect operations if more than two Web Services are involved (the global model).

While not based on the WSDL framework and syntax, WSCI is defined as an extension of WSDL 1.1 to describe the relations between the WSDL operations and is introducing an ad-hoc syntax expression to address them. It is important to notice that Using Qualified Names (QNames) as Identifiers in Content is being considered by the Technical Architecture Group (TAG), and their use in WSDL is under discussion in the Web Services Description Working Group (see the minutes of the 12 June 2002 face-to-face meeting). While addressing the interactions and the correlations, WSCI does not associate semantics with them. However, these semantics may be described at a different level such as the discovery level.

The WSCI specification abstract:

The Web Service Choreography Interface (WSCI) is an XML-based interface description language that describes the flow of messages exchanged by a Web Service participating in choreographed interactions with other services.

WSCI describes the dynamic interface of the Web Service participating in a given message exchange by means of reusing the operations defined for a static interface. WSCI works in conjunction with the Web Service Description Language (WSDL), the basis for the W3C Web Services Description Working Group; it can, also, work with another service definition language that exhibits the same characteristics as WSDL.

WSCI describes the observable behavior of a Web Service. This is expressed in terms of temporal and logical dependencies among the exchanged messages, featuring sequencing rules, correlation, exception handling, and transactions. WSCI also describes the collective message exchange among interacting Web Services, thus providing a global, message-oriented view of the interactions.

WSCI does not address the definition and the implementation of the internal processes that actually drive the message exchange. Rather, the goal of WSCI is to describe the observable behavior of a Web Service by means of a message-flow oriented interface. This description enables developers, architects and tools to describe and compose a global view of the dynamic of the message exchange by understanding the interactions with the web service.