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Interface Definition for the Web
INDUSTRY REPORT
WIDL:
MARK G. WALES
webMethods Inc.
Web standards like HTTP, HTML, and XML have given business enterprises a de facto standard for open data interchange. While there are many tools to help automate the conversion
of legacy or database information to Web-based formats, there are few to assist in the real-time automated retrieval of that data and its conversion to an application-specific format. Since most Web-based interchanges occur between a browser and a Web server, automating these exchanges can help integrate Web-based information into existing applications.
This is the premise underlying the Web Interface Definition Language. WIDL was developed by webMethods to abstract automated HTTP-based exchanges into a simple functional interface. WIDL services make it easier for both programmers and Webmasters to incorporate Web-based data and functions into their work. But beyond developing services around Web sites, WIDL can also be part of a larger architecture that puts an XML front end on a broad array of back-end applications and data sources. This report describes WIDLs structure, implementation, and use as a building block for distributed computing on the Web.
THE XML IN WIDL
XML supports the definition of language- and platform-neutral facilities, and WIDL uses it to create a language for defining interfaces for Web-based interactions. The XML in WIDL contains tags or attributes that identify (among other things)
n a unique name for the Web-based exchange being defined;
n the URL of the Web site being mapped;
n the type of HTTP request to be sent;
n the values to be transmitted along with the HTTP request;
n the subset of the response that is interesting to the application; and
n the error processing to be done if the response does not match what is anticipated.
webMethods developed an XML-based solution to automating exchanges between Web clients and servers. The Web Interface Definition Languageor WIDL, as it is calledis part of an extensible framework that integrates diverse applications over the Web.
IEEE INTERNET COMPUTING 1089-7801/99/$10.00 1999 IEEE http://computer.org/internet/ JANUARY FEBRUARY 1999
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W E B O B J E C T M O D E L S
The XML tags that define WIDL are a set of identifiers crafted specifically to describe the domain of...