A revised version 1.0 working draft for Web Service User Interface (WSUI) 1.0 was published July 26, 2002. "WSUI is a component model for adding presentation and multistage interaction to XML and SOAP-based network services. WSUI is designed to be lightweight and easily implementable by using standard XML technologies such as XSLT, XPath, and XHTML."
A collection of references for (model-driven, device-independent, client-based) interactive GUIs is available in the document "XML Markup Languages for User Interface Definition."
[June 27, 2001] A communiqué from Chad Williams (Epicentric, Inc.) announces the release of 'WSUI' as an open standard "for the presentation of Web services as user interface components that can be delivered as Web applications to end users." The WSUI developers "are part of a working group formed to review and comment on the specification; once the specification has been reviewed and commented on by all interested parties, the resulting work will be submitted for standardization." Participation in the working group is welcome. A working draft document "describes the syntax and semantics of Web Service User Interface (WSUI). WSUI is a component model for adding presentation and multistage interaction to XML and SOAP-based network services. It is designed to be lightweight and easily implementable by using standard XML technologies such as XSLT, XPath, and XHTML." Rationale for the design is provided in the specification Introduction: "XML-based network services have become a very popular application integration mechanism. The aggregation and integration of these services at the presentation layer (such as HTML) is increasingly performed by non-technical or semi-technical business users. However, most standards for integrating or consuming XML-based network services are designed for a developer audience and are intended principally for RPC communication between server applications. A number of vendor-specific approaches have emerged to facilitate non-developer integration of network services, particularly to aid in the construction of e-commerce and portal web sites. WSUI is an attempt to standardize this 'last mile' of integration by defining a web component model that couples network services with interaction and presentation information. These components can be dynamically embedded into container applications at run-time by non-developers." WSUI's goal is "to enable a simple mechanism for integrating applications which are remotely exposed as XML and SOAP Web services into a Web site. Simplicity and elegance are the key technical goals, and the specification has been made simple enough that it can pass the 'weekend test' -- a single programmer working for one weekend can create an implementation." Other industry partners participating in the WSUI initiative include Documentum, Intraspect, Jamcracker, NewsEdge, Securant, and Yellowbrix.
From the draft specification: "WSUI consists of these key concepts: (1) Components and containers; (2) Pages and views; (3) Events and interaction flow; (4) Component views using XSLT; (5) Variables and expressions. WSUI defines the concept of a component. A component is a platform-independent web application that can respond to end-user interactions, invoke network services, process the results, and generate end-user display code, such as HTML or WML. WSUI defines the concept of a container. A container is an end-user application, such as a web site or portal, that includes a runtime environment that allows components to be dynamically embedded into the container. Components are defined via an XML format described in this document. Besides the component's XML definition, the only other physical asset of a component are its XSLT stylesheets, which are referenced by URL within the XML definition. The XML definition tells the container what user actions the component can respond to, what network services to invoke, and how to render the end-user display. A container need only know the URL to a component's XML definition to be able to integrate it. While the container may cache the component definition and stylesheets, the canonical definition remains at that URL; when the component's owner modifies the component's XML definition or stylesheets, the component should change on all containers that have integrated that component. WSUI does not define any characteristics of the container outside of those necessary to generate the component output. WSUI places no restrictions on how the component is used within the container. WSUI does not define the placement of the component's display within the container's enclosing display, if any."
References:
[July 26, 2002] Web Service User Interface (WSUI) 1.0 Working Draft. July 26, 2002. XML Schema in text view and graphical documentation.
WSUI Specification. Version: 1.0 Working Draft. Date: July 17, 2001. With W3C XML Schema, [cache]
Announcement 2001-06-28: "Epicentric and Industry Leaders to Define First User Interface Standard for Web Services. Documentum, Intraspect, Jamcracker, NewsEdge, Securant, and Yellowbrix Join Forces to Develop Web Services User Interface (WSUI) Standard."
[November 21, 2001] "New Standard Closes the Loop for Web Services." By Ed Anuff. In eai Journal Volume 3, Number 11 (November 2001), pages 16-17. ['Web Services User Interface (WSUI) describes SOAP and XML interfaces as multi-page end-user applications that can be embedded in Web sites. It provides a reusable approach to Web application integration.'] New standards are emerging to let companies build applications that work together using eXtensible Markup Language (XML) messaging. The standards include: Simple Object Access Protocol (SOAP); Web Services Description Language (WSDL); Universal Description, Discovery, and Integration (UDDI); Web Services User Interface (WSUI). These standards provide a good foundation for machine-to-machine communication and will help XML Web services usher in the next-generation Internet. WSUI is especially valuable because it addresses the lack of a standard user-interface layer for Web services. The proposed WSUI standard lets Web services with SOAP-Remote Procedure Call (RPC), XML, or WSDL SOAP interfaces be described as complex, multi-page, end-user applications that can be easily embedded in Websites. WSUI leverages the benefits of an XML-based interface to an application -- benefits that make Web services an ideal machine-to-machine transport layer. Among the benefits are separating implementation from interface and enabling diverse implementation platforms to interoperate. By standardizing the display layer of Web services, vendors can more easily embed their applications in Web application delivery platforms without expensive, vendor-specific implementations... WSUI leverages the basic XML technologies supported in open-source toolkits such as the Apache XML project as well as vendor toolkits that implement core XML specifications. WSUI is specifically engineered to expose components, which expose any number of end-user views in a browser. Usually, the purpose is supporting form and menu-driven user interaction with back-end services. A WSUI component can call XML, SOAP RPC, and WSDL SOAP services. More service types can be easily added in the future. WSUI's creators acknowledge that many Web services will never be interacted with via a user interface. Nevertheless, many services that end users and customers want to aggregate are user-facing. That's where WSUI is beneficial because it offers a standard mechanism for integrating user-facing services via standards- based XML messaging... WSUI makes several key assumptions about the interested parties. A service provider exposes any number of XML or SOAP services. A service consumer is a Web publishing platform or portal, which is running a WSUI container implementation and constructs Web pages based on user requests. Users interact with Web pages to interact with a WSUI service. Architecturally, WSUI assumes that the services exposed via XML or SOAP exist as-is. For a Web publishing platform to integrate the service as an application that can be accessed by end-users requires only a WSUI descriptor file plus a series of XML Stylesheet Language Transformation (XSLT) templates. Developers can create the actual WSUI file and XSLT templates needed to integrate existing services. An application or service vendor can package the WSUI/XSLT files with a standard interface to facilitate other Websites embedding their applications..." [cache]
