[June 15, 2002] On June 13, 2002 a web services choreography specification was released jointly by BEA Systems, Inc., Intalio, Inc., SAP AG, and Sun Microsystems, Inc. The review draft Web Service Choreography Interface 1.0 specification "proposes a language standard that can be used in conjunction with existing Web-service protocols to provide a description of the observable behavior of Web services. 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."
Bibliographic information: Web Service Choreography Interface 1.0. By BEA Systems, Intalio, SAP, and Sun Microsystems. 102 pages. Copyright to BEA Systems, Inc., Intalio, Inc., SAP AG, and Sun Microsystems, Inc. Authors: Assaf Arkin (Intalio); Sid Askary (Intalio); Scott Fordin (Sun Microsystems); Wolfgang Jekeli (SAP); Kohsuke Kawaguchi ( Sun Microsystems); David Orchard (BEA Systems); Stefano Pogliani (Sun Microsystems); Karsten Riemer (Sun Microsystems); Susan Struble (Sun Microsystems); Pal Takacsi-Nagy (BEA Systems); Ivana Trickovic (SAP); Sinisa Zimek (SAP).
Problem and rationale for the WSCI solution: "The current Web Service stack does not define a choreography language or any other relationship among atomic operations. It does, however, provide the basic layers: (1) SOAP defines the basic formatting of a message and the basic delivery options. A SOAP compliant Web Service knows how to send and receive SOAP-based messages (2) WSDL describes the static interface of a Web Service. It defines the protocol and the message characteristics of end points by means of four basic operations; a WSDL compliant Web Service knows how to support any of these four operations. The operations defined in this way: [A] Are atomic in nature (that is, no intermediate state is visible from the outside) [B] Describe the direction of messages (incoming or outgoing) but not the behavior of the service as a result of each individual operation... The current Web Service technologies may be adequate for simple information retrieval in a stateless message exchange, such as a stock quote Web Service; for some services, it may even be sufficient for messages to maintain state in remote procedure calls by passing tokens or state variables within objects. ... the challenge for WSCI is to provide answers to the previous (and other related) questions in the domain of the Web based computing. Fundamentally, the challenge will be to describe Web Services: (1) From an external point of view (without knowing how internally they operate); (2) Independently of any particular integration model (workflow, MOM etc); (3) Precisely enough to allow other components to have a clear understanding of how to properly interact with them; (4) In the context of each specific message exchange in which they participate... To be part of a useful and manageable Web Service collaboration, individual operations must be allowed to convey enough information about how they can be used in a given scenario in order to enable them to participate in more complex processes. WSCI achieves this by defining a layer on top of the existing Web Service stack..." [Spec Section 1]
From the 2002-06-26 announcement: "BEA Systems, Intalio, SAP AG, and Sun Microsystems today announced the publication of the XML-based Web Service Choreography Interface (WSCI). This new specification is available for public comment at the companies' respective Web sites. WSCI provides an important foundation for realizing the promise of Web services to deliver automated, application to application collaboration... WSCI describes the flow of messages exchanged by a Web service in a particular process, and also describes the collective message exchange among interacting Web services, providing a global view of a complex process involving multiple Web services. Today's service description languages are adequate for simple information retrieval, such as a stock quote, but they do not provide the rich behavioral detail that describes the role the service plays as part of a larger, more comprehensive collaboration. One of the key benefits of WSCI is that it bridges the gap between business process management and Web services by describing how a Web service can be used as part of a larger, more complex business process. These business processes may reside entirely within the confines of a single company, or span across multiple organizations or companies. After a public review period, WSCI will be submitted, on a royalty-free basis, to an industry standards body..."
From the Spec v1.0 Overview:
WSCI describes how Web Service operations -- such as those defined by WSDL can be choreographed in the context of a message exchange in which the Web Service participates. Interactions between services -- either in a business context or not -- always follow and implement choreographed message exchanges (processes). WSCI is the first step towards enabling the mapping of services as components realizing those processes.
WSCI also describes how the choreography of these operations should expose relevant information, such as message correlation, exception handling, transaction description and dynamic participation capabilities.
WSCI does not assume that Web Services are from different companies, as in business-to-business; it can be used equally well to describe interfaces of components that represent internal organizational units or other applications within the enterprise. Again, WSCI does not address the definition of the process driving the message exchange or the definition of the internal behavior of each Web Service.
WSCI describes the interdependencies among the Web Service's operations so that any client:
- Can understand how to interact with such service in the context of the given process; and
- Can "anticipate" the expected behavior of such service at any point in the process' lifecycle.
Being able to describe the dynamic interface of a service in the context of a particular process enables the developer/architect to abstract from the implementation and to focus on the role the Web Service plays in such process.
"WSCI provides an important foundation for realizing the promise of Web services to deliver automated, application-application collaboration. One of the key benefits of WSCI is that it bridges the gap between business process management and Web services by describing how a Web service can be used as part of a larger, more complex business process. These business processes may reside entirely within the confines of a single company, or span across multiple organizations or companies." [website main page description]
Principal References:
- WSCI 1.0 as a W3C Note:
- Web Service Choreography Interface (WSCI) 1.0. W3C Note 8-August-2002.
- WSCI Submission request
- W3C Staff comment from Philippe Le Hégaret (Team contact for the Web Services Description Working Group)
- Sun ONE Web Service Choreography Interface Editor. By Oran Kelly. Product Version: 0.9 Alpha. Release Date: June 27, 2002. System Requirements: Java Development Kit (JDK) 1.4 or later. "The Sun ONE Web Service Choreography Interface Editor is a free tool that lets you describe the choreography of a Web service by building the a WSCI definition through a simple graphical interface."
- "BEA, Intalio, SAP, Sun Publish Web Services Choreography Interface, Take Web Services Collaboration to New Level. New XML-Based Specification Helps Developers Build Web Services for Open Application to Application Collaboration." 'WSCI will be submitted, on a royalty-free basis, to an industry standards body...'
- WSCI website at Sun Microsystems
- WSCI website at Intalio. Alternate URL.
- WSCI website at SAP AG
- WSCI website at BEA Systems
- WSCI Spec version 1.0 (HTML) [cache]
- WSCI Spec version 1.0 (PDF) [cache]
- XML Schemas (from WSCI spec Section 8.4)
- WSCI FAQ document
- Feedback: send email to any of: BEA Systems (wsci@bea.com), Intalio (wsci@intalio.com), SAP AG (wsci-feedback@sap.com), or Sun Microsystems (wsci-feedback@sun.com). ['In order to finalize the collaborative WSCI specification, all feedback will be sent to BEA Systems, SAP AG, and Sun Microsystems as detailed in the Privacy Policy.']
- WSCI feedback form [Sun]
Related References: [see also the FAQ document]
- "Web Services Description Language (WSDL)"
- "Business Process Modeling Language (BPML)"
- "Business Process Specification Schema Project" and BPSS v1.01 spec
- Business Transaction Protocol (Primer), and TC
- "Web Services Flow Language (WSFL)"
- "XLANG"
- "Web Services Conversation Language (WSCL)"
- Enterprise Distributed Object Computing (EDOC)
- XML Pipeline Definition Language
Articles, Commentary, News, Product Information:
[July 03, 2003] "Web Services Orchestration and Choreography. A Look at WSCI and BPEL4WS." By Chris Peltz (HP Developer Resources Organization). In Web Services Journal Volume 3, Issue 7 (July 2003), pages 30-35. With 4 figures. "The two standards discussed here -- the Web Service Choreography Interface (WSCI) and Business Process Execution Language for Web Services (BPEL4WS) -- are designed to reduce the inherent complexity of connecting Web services together. Without them, an organization is left to build proprietary business protocols that shortchange true Web services collaboration. Recently, the terms orchestration and choreography have been employed to describe this collaboration: Orchestration refers to an executable business process that may interact with both internal and external Web services. Orchestration describes how Web services can interact at the message level, including the business logic and execution order of the interactions. These interactions may span applications and/or organizations, and result in a long-lived, transactional process. With orchestration, the process is always controlled from the perspective of one of the business parties. Choreography is more collaborative in nature, where each party involved in the process describes the part they play in the interaction. Choreography tracks the sequence of messages that may involve multiple parties and multiple sources. It is associated with the public message exchanges that occur between multiple Web services. Orchestration differs from choreography in that it describes a process flow between services, controlled by a single party. More collaborative in nature, choreography tracks the sequence of messages involving multiple parties, where no one party truly 'owns' the conversation. In this article, I'll highlight key technical requirements for Web services orchestration and choreography, and point out key standards used to meet these needs... While BPEL4WS supports the notion of 'abstract processes,' most of its focus is aimed at BPEL4WS executable processes. BPEL4WS takes more of an 'inside-out' perspective, describing an executable process from the perspective of one of the partners. WSCI takes more of a collaborative and choreographed approach, requiring each participant in the message exchange to define a WSCI interface. At the same time, WSCI and BPEL4WS both meet many of the technical requirements outlined earlier. They both provide strong support for persistence and correlation to manage conversations. WSCI and BPEL4WS also describe how exceptions and transactions should be managed. From a usability standpoint, WSCI does have a somewhat 'cleaner' interface than BPEL4WS. Some of the difficulties in using BPEL4WS are attributed to the fact that the language includes artifacts from both XLANG and WSFL, each of which took a different approach to workflow... Orchestration and choreography are terms related to connecting Web services in a collaborative fashion. The capabilities offered by the available standards will be vital for building dynamic, flexible processes. The goal is to provide a set of open, standards-based protocols for designing and executing these interactions involving multiple Web services. Many vendors have announced support for BPEL4WS in their products, and the OASIS technical committee is looking to move this specification going forward. WSCI is being considered by the W3C for Web services choreography. While BPEL4WS has defined a notion of choreography through abstract processes, it is still unclear whether this will be accepted over the W3C work. Clearly, market adoption will be driven by the direction taken by vendors and their support of the standards in their product implementations. As these standards take shape, it will be important to pay close attention to the direction taken by standards bodies such as the W3C and OASIS..." [alt URL]
[March 18, 2003] "Microsoft Dips Toe in Choreography Waters. Software Giant Surprise Attendee at W3C Meeting." By Paul Krill. In InfoWorld (March 14, 2003). "Microsoft on Thursday [2003-03-13] participated in an industry effort to standardize Web services choreography. Despite initial indications that it would not attend, two Microsoft representatives attended the first meeting of the World Wide Web Consortium's (W3C) Web Services Choreography Working Group held Thursday and Friday at Oracle headquarters in Redwood Shores, Calif. , an Oracle representative said. Microsoft, in a prepared statement pertaining to its attendance, provided little detail on specific goals of its participation and confirmed it still will not formally join the campaign. 'We are interested in following and, when appropriate, participating in working groups. As such, we had two employees attend part of the meeting in order to understand its scope better. No decisions have been made regarding joining. Moving forward, Microsoft continues to stay actively involved on the many different fronts, with varying degrees of participation and input, relative to the standardization process,' the company said. Oracle's representative said that Microsoft is seeking a single standard that that finds a middle ground between the BPEL4WS (Business Process Execution Language for Web Services) specification, authored by Microsoft, IBM, and BEA Systems, and the Sun Microsystems-led WSC (Web Services Choreography Interface) specification. Microsoft wants to have the W3C effort complement BPEL4WS, according to Oracle. Web services choreography is intended to automate interaction between Web services and is considered critical to enabling the integration promise of Web services. Attending on behalf of Microsoft were Alan Brown, who serves as one of the company's W3C representatives, and Greg Meredith, who is in Microsoft's research organization, according to Oracle... Microsoft, IBM, and BEA have not formally submitted BPEL4WS to a standards organization for consideration, unlike WSCI, which is now being considered by W3C. Despite Microsoft's willingness to work with the W3C working group, BPEL4WS still is not being submitted to the organization, according to the Oracle representative. However, BPEL4WS is gaining industry support despite not being under the jurisdiction of any standards organization. It is being implemented in products from companies such as Collaxa and BEA, who are not including WSCI in their systems, despite BEA also being a co-author of WSCI. A Sun representative said it is still too early to see much WSCI support at the product level..."
[March 07, 2003] "Web Services in Serious Jeopardy. [Reality Check.]" By David Berlind. In ZDNet Tech Update (March 06, 2003). Includes sections: 'BPEL4WS vs. WSCI' and 'Penchant for patents?' "APIs are the basis of Web services. Microsoft and IBM played a critical role in making sure that the first Web services protocol necessary to get the ball rolling -- the Simple Object Access Protocol (SOAP) -- was compatible with both of their solutions. Sure, the promise of interoperability and cost savings via Web services is intriguing to IT shops. But the vendors have another motive in establishing a standard set of insulating APIs. Creating a more level playing field in the cost of switching vendors is less hazardous, and potentially favors those companies with the most market clout... Unfortunately for the vendors who want to steal each other's customers and the customers who want to benefit from that war, there's a small problem. And, if the problem is not resolved soon, the entire Web services plan could end up being scuttled. The bandeleros, whose assistance is imperative, were on board with the preliminary plans--the first few Web services APIs (XML, SOAP, WSDL, etc.). Those basic APIs are essential for dissimilar systems to hold hands, but another set of APIs is essential to making sure that those systems can go to the next level--dance. In particular, to the extent that multiple systems are involved in the processing of a transaction or series of transactions, the order of execution of every step is imperative, as is the application's response if one of those steps fails. Whereas enterprise databases have long been capable of tracking transactions and rolling back data to its pre-transaction state should an error occur, choreographing a business process that involves multiple dissimilar systems, and then building in a similar degree of fault tolerance, is far more complex. These dissimilar systems -- dance partners, if you will -- would need a common API if the dance were to result in an award-winning performance (successful transaction execution or roll-back) each and every time. It is this API and the current disagreement over it that is threatening the future of Web services. In one corner is the Business Process Execution Language for Web Services (BPEL4WS, but most often pronounced 'bee-pell'). BPEL4WS is a business process and choreography API that was co-authored by IBM, Microsoft and BEA. Although it is completely proprietary and hasn't even been submitted to a standards-setting body, all three companies already have plans to support the specification in their solutions as though it were a standard. At the very least, IBM and Microsoft will be able to continue focusing on picking off each other's customers as well as BEA's. Unfortunately, while the three companies steam forward on BPEL4WS, the rest of the world is standing in the other corner with a competing specification--the Web Services Choreography Interface (WSCI, pronounced 'whiskey). Unlike BPEL4WS, WSCI has taken the first step towards standardization through a submission to the World Wide Web Consortium (W3C)... Let's suppose that BPEL4WS becomes the de facto standard, by virtue of BEA's, Microsoft's, and IBM's support for BPEL4WS in their application servers, which happen to be the application server market's three leading products. The three intellectual property owners would be in the driver's seat not only when it comes to Web services, but for a portion of the Web itself. It will be exactly the scenario that I've warned about, where the intellectual property owners of one critical protocol could end up in control of an important part of the Internet. At the very least, if you end up being seduced by the promise of standards by using the two Web services protocols (SOAP and WSDL) that IBM and Microsoft shoved down the W3C's throat, it may not be long until you find out that your investment in open standards has locked you into using a proprietary technology. As I have posited before, following a path where you eventually find yourself locked into a proprietary technology puts the intellectual property owner in control of a lot of things, including cost..."
[July 02, 2002] "BEA, Intalio, SAP and Sun Advocate a Drop of WSCI." By Nick Patience. the451, Special to SearchWebServices.com. "The battle for the layers above the relatively established core Web services standards has a new player in the form of a standard proposed by BEA, Intalio, SAP and Sun. It's called the Web Service Choreography Interface (WSCI, pronounced like the drink) and it is meant to help track the sequence of messages, logical dependencies and exception handling that will occur when applications are made up of multiple Web services from potentially multiple sources. Put simply, it describes the behavior a developer can expect from a Web service by interacting with it. Given the number of competing would-be standards and the amount of noise in this space, it is equally important to say what WSCI is not, in addition to defining what it is. It is not a specification to dictate the assembly of composite Web services applications, nor is it a high-level workflow specification, nor something to define a gateway. In the words of the specification description itself, it is concerned solely with the 'observable behavior' of a Web service, not the process by which it was created... As with all standards, WSCI's success or failure will not necessarily depend on how good the technology is, but who supports it. And while the three major vendors here are a good start, the group knows it needs much wider support. As the451 has been illustrating for some time, this typically involves IBM and Microsoft setting the pace and others following. However, with Sun's adoption of the IBM and Microsoft-led WS-Security format this week and now this attempt to recapture its earlier reputation for defining standards -- with Java being the shining example -- BEA and Sun at least have a stake in the ground in what will be a very important area in determining the success or failure of Web services. For its part, IBM considers WSCI to be a subset of BPML, which has been around for a couple of years. It says that while it is still early on in the workflow and business process languages space, it believes the industry will consolidate within 6-12 months around a unified standard, at least in a draft form. If that timetable is accurate, of course, it doesn't give WSCI a whole lot of time. Following a public comment period driven from the four companies' websites, the group says they intend to submit WSCI to a standards organization on a royalty-free basis. Although Sun would not indicate its preference, the favorites would seem to be OASIS or the W3C. Products: Intalio, which first launched two years ago, is gearing up to relaunch soon with WSCI as part of its five-piece n3 business process management implementation, but details are scarce right now. Sun is about to release a free WSCI editor for developers... From what is currently known, WSCI seem more broadly applicable than the prospective BPM and workflow standards. It is a chance for BEA and Sun to reclaim some of the standards-defining high ground from IBM and Microsoft. However, IBM and others that are not behind this yet could use the similarity between aspects of WSCI, WSFL and XLANG as a reason to not bother supporting it and in doing so, attempting to freeze out Sun once more. Until some of the three large companies here implement it, WSCI's credentials will be doubted..."
[June 26, 2002] "Sun, Others Propose New Web Services Standard." By Matt Berger. In InfoWorld (June 26, 2002). "Sun Microsystems and a group of software vendors are proposing to add another standard to the recipe for building Web services. On Wednesday, the companies detailed a specification that would allow developers to "choreograph" events and transactions that take place between computers when applications and services are accessed over the Internet. The specification is called the Web Service Choreography Interface (WSCI), and it is designed to work with Web services based on the standard data format XML (Extensible Markup Language). Joining Sun in drafting and publishing the specification are software makers SAP, BEA Systems and Intalio. For Web services that make use of several existing Web-based applications, the specification aims to define a standard way for developers to describe which actions must occur and in what order they must take place, so that the Web service they are building can process information in an orderly manner, said Karsten Riemer, an XML architect with Sun. For example, a Web site where users can book airline tickets online might require an application that combines existing Web services for various tasks, such as determining whether the user is a member of a frequent flier program, figuring out which airlines fly to the destination being requested, and checking that the user has sufficient funds in his or her bank account to purchase the ticket..."
[June 26, 2002] "Sun, BEA, Others Publish New Web Services Specification. Sun to Offer Free Tool Around WSCI." By Elizabeth Montalbano. In Computer Reseller News (June 26, 2002). ['Several industry vendors Wednesday unveiled a new XML-based specification to facilitate Web services interoperability.'] "Sun Microsystems, BEA Systems, Intalio and SAP have made the new spec, Web Service Choreography Interface (WSCI), available for review on their Web sites, said Susy Struble, manager of XML industry initiatives at Sun. To help solution providers and developers become familiar with WSCI, Sun will release a new tool, the Sun ONE Web Service Choreography Interface Editor, on its Web site Friday for free download, she added. Karsten Riemer, a Sun XML architect, said WSCI picks up where WSDL leaves off in describing what a Web service does. For instance, WSDL will describe the functions of a particular service, but not how those functions relation to each other, said Riemer. 'WSCI describes all the relationships between all the things you can do [with a Web service],' said Riemer. 'It's the sequence of steps, the glue around individual WSDL operations.' Struble said Sun and the companies that developed WSCI hope to submit the spec to a standards body such as the W3C once companies have had a chance to review WSCI... Struble said Sun is 'pleased to be taking a leadership' role in promoting Web services interoperability with the WSCI spec. She would not comment on whether the spec would become a part of the blueprints WS-I is developing to promote interoperability..."
Intalio Product Overview. "Business Process Management System." 14 pages. "... Intalio has developed the Intalio Business Process Management System that helps companies manage their discrete & transactional business processes, over their entire life-cycle. Intalio helps Global 2,000 firms reduce their process design-to-production cost, control their total cost of process ownership, and increase their strategic return on process investment . Quite simply, Intalio is the first platform designed for the process-managed enterprise. Intalio, The Business Process Management Company, is a leading provider of Business Process Management Systems that help Global 2,000 firms reduce their process design-to-production cost, control their total cost of process ownership, and increase their strategic return on process investment. Intalio is the founder of the Business Process Management Initiative (BPMI.org) and the main author of the BPML and WSCI industry standards..."
"WSCI." 2002-06-17 or later. Commentary by Jean-Jacques Dubray on ebPML.org, "a website dedicated to the architecture and technologies of Business Process Management Systems (BPMS)." From the Summary: This month (June 2002), Intalio has released a new specification WSCI, the Web Service Choreography Interface....As there have been some comments made with respect to the relationship between WSCI and ebXML (BPSS in particular). I review WSCI with the perspective of an ebXML implementer and try to identify what does it mean for me. In particular, I am not trying to identify the merits of WSCI with respect to WSFL or XLANG. At the first level, WSCI provides a way to describe the behavior of a Web Service (from a flow, transaction, correlation perspective...). At the second level, with the concept of global model, they provide the ability to "link" operations in a collaboration. The main focus of the specification is application-to-application integration, not in the EAI sense where loose coupling is the primary goal, but in a relatively tightly coupled fashion: namely how two APIs which have been web service enable cooperate with each other. The typical example they give is a travel agent / airline integration to deliver a common experience to a customer. The spec does not offer any specific semantics relative to 'Business Transactions', they are treated as regular system-to-system transaction. In particular, there is no attempt to guarantee state synchronization between the two parties using a specific protocol like in BPSS. I feel that this spec has very limited applications, typically like the one in the example. It cannot be used effectively to model general B2B and EAI scenarios. In terms of choreography it does not really bring anything new. Since it is coming directly from BPML, it bears a lot of similarities with XLang (block structured). So far, I still think that WSFL is the best thought out choreography model. The novelty, if that can be considered a novelty is the BPML correlation, transaction and exception model..."
[June 15, 2002] "Web Services Specification to Target Collaboration." By Paul Krill. In InfoWorld (June 14, 2002). "Sun Microsystems, SAP, BEA Systems, and Intalio have developed an XML-based interface description language to describe the flow of messages exchanged in Web services called the WSCI (Web Service Choreography Interface). According to information on Sun's Web site, 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 describes the observable behavior of a Web service in terms of temporal and logical dependencies among exchanged messages. Sequencing rules, correlation, exception handling, and transactions are features. A global, message-oriented view of interactions is provided. The behavioral description provided by WSCI enables developers, architects, and tools to describe and compose a global view of the dynamic of a message exchange by understanding interactions with the Web service, according to Sun's site. Analyst Joanne Friedman, vice president of e-business strategies at Meta Group in Toronto, described WSCI as 'an XML-based language to describe the flow of messages exchanged by a Web service, but in the context of a higher level business process.' WSCI is critical to collaboration in applications such as e-business, Friedman said. The technology would be used to look at the behavioral patterns of messages and the expectations of senders and receivers... In an e-commerce transaction, WSCI would enable a buyer or merchant conducting a transaction to query the Web for a set of carriers to deliver the merchandise..."
