XML Glossary

XML Glossary

December 1999

Because XML is so important across the industry, Microsoft Corp. put together this quick cheat sheet for you to keep handy when you’re writing about XML and related technologies. The following definitions are designed to give you an understanding of what these products and technologies are and why they’re important. We have also included some links that can provide more information.

Extensible Markup Language (XML): XML is a universal method for representing structured information (spreadsheets, address books, technical information, etc.) in a way that is especially well-suited to moving data in a distributed computing environment. With XML, developers can specify the of a document, for example, the document’s title, its author or a list of related links. Most important, XML provides a way of separating data from the methods that act on it and the way it is presented.

Document Object Model (DOM): The Document Object Model is a platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content, structure and style of XML (and HTML) documents. The goal of the DOM specification is to define a programmatic interface for XML and HTML.

What are style sheets? Cascading style sheets (CSSs) and the Extensible Stylesheet Language (XSL) are ways to achieve more control in the presentation of HTML and XML documents.

Cascading style sheets: CSSs are a style sheet mechanism that has been specifically developed to meet the needs of Web designers and users. Put simply, they give designers control over typefaces, font sizes, leading (line spacing), position and other aspects of presentation.

Extensible Stylesheet Language: XSL is a language for expressing style sheets. It consists of two parts: XSLT, a language for transforming XML documents, and an XML vocabulary for specifying formatting semantics.

What are XSL transformations (XSLT) and XML Path Language (XPath)? XSLT is language for describing rules for transforming XML documents into other XML documents. The new XML document can be completely different from the original. In addition, in constructing the new document, elements from the original document tree can be filtered and reordered, and arbitrary structure can be added.

XPath is a language for addressing parts of an XML document, designed to be used by both XSLT and a future specification called XPointer, which further defines how to address the text contents of XML documents.

Document type definitions (DTDs): A DTD is a set of syntax rules for tags. It tells which tags can be used in a document, the order in which they should appear, which tags can appear inside others, which tags have attributes, and so on. Because XML is not a language itself but rather a system for defining languages, it doesn’t have a universal DTD the way HTML does. Instead, each industry or organization that wants to use XML for data exchange can define its own DTDs.

XML schemas: A schema, like a DTD, is a way to define a set of XML elements and attributes and the rules for their correct combination. However, XML schemas provide a superset of capabilities found in DTDs. In particular, XML schemas provide support for datatypes and namespaces.

XML namespaces: XML namespaces provide a simple method for uniquely qualifying element and attribute names used in XML documents by associating them with namespaces identified by URI references. This allows developers to combine information from different data structures in a single XML document without
between element names. For example, if one attempts to combine book information and author information in a single document, a conflict between the
of the book and the
of the author could result. XML namespaces solve this problem.

How is XML related to Standard Generalized Markup Language
(SGML) and HTML? SGML is a way of expressing data in text-processing applications. Both XML and HTML are document formats derived from SGML. HTML is an application of SGML, whereas XML is a subset of SGML. The distinction is important: HTML can’t be used to define new applications, but XML can. HTML, SGML and XML will continue to be used where appropriate; none of them will render the others obsolete.

Simple Object Access Protocol (SOAP): SOAP enables applications to talk to Web services as though they were applications. The specification will allow Web sites to become sophisticated applications that can be accessed programmatically as well as through a browser. SOAP is Internet-savvy, open standards-based and easy to work with because it is easily readable by humans.

Microsoft BizTalk Framework: The Microsoft® BizTalk TM Framework is a comprehensive XML-based implementation framework developers can use to design and implement solutions based on a Web Services Architecture. It helps establish a set of guidelines for the publishing of schemas in XML and the use of XML messages to easily integrate software programs to build rich, new Web-based solutions.

Microsoft BizTalk Server: BizTalk Server provides the tools and infrastructure companies require to exchange business documents among various platforms and operating systems, regardless of the application being used to process the documents. Using BizTalk Server, companies can easily exchange documents between applications within their own organization. BizTalk Server also provides a standard gateway for sending and receiving documents via the Internet. By taking advantage of BizTalk-compatible messages and compliant schemas, BizTalk Server enables organizations to conduct business online effectively and efficiently.

XML parser: An XML parser is the piece of software that reads XML files and makes the information from those files available to applications and programming languages, usually through a known interface like the DOM (see above). The XML parser is responsible for testing whether a document is well-formed and, if given a DTD or XML schema, it will also check for validity (i.e., it determines if the document follows the rules of the DTD or schema). Microsoft includes a validating XML parser with the Windows® 2000 operating system and Microsoft Internet Explorer 5 browser software.

More Information Sources

Microsoft, BizTalk and Windows are either registered trademarks or trademarks of Microsoft Corp. in the United States and/or other countries/regions.

Other product and company names herein may be trademarks of their respective owners.

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