Web Glossary

February 19, 1999

A B C D E F G H I J K L M N O P Q R S T U V W	X	Y Z

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• XLL (Extensible Link Language)
  An outgrowth of Extensible Markup Language (XML), an XLL is a stand-alone dynamic-link library (DLL). A DLL is a code resource that allows executable routines to be stored separately and be loaded only when needed by a program. DLLs and XLLs are separate files that allow programmers and Web authors to make changes to only that module without affecting the operation of the calling program or any other DLL or XLL.
• XML (Extensible Markup Language)
  XML, is a simplified subset of Standard Generalized Markup Language (SGML) that provides a file format for representing data, a method for describing data structure, and a mechanism for extending and annotating HTML with semantic information. Allowing an unlimited set of tags, XML tags indicate what kind of data each tag contains, rather than indicating how something should look. For instance, a tag might hold a price, an order number, or a name. The flexibility of XML allows the document's author to determine what kind of data to use and to choose the tag types that most fit the author's needs.

  As a universal data format, XML provides a standard for the server-to-server transfer of different types of structured data so that the information can be decoded, manipulated, and displayed consistently and correctly. In addition, it enables the development of three-tier Web applications, acting as the data transfer format between the middle-tier Web server and the client.

• XML-Data
  XML-Data is a submission to the World Wide Web Consortium that was co-authored by Arbortext, DataChannel, Inso, and Microsoft. It outlines an XML syntax for schemas that define the characteristics of class.

  In the case of XML, schemas define the characteristics of the XML document. In this sense, they are similar in functionality to DTDs. However, unlike DTDs, the schemas described in the XML-Data submission allow for data-types and inheritance. In addition, because these schemas are written in XML, they are easily extensible.

• XML data type
  In XML, a data type indicates that the contents of an element can be interpreted both as a string and as a typed value (a number, date, etc). The data type of an XML element indicates that the element's contents can be parsed or interpreted to yield an object more specific than a string. Universal Resource Identifiers (URIs) identify datatypes. The URI is simply a reference to a section of a document that defines the appropriate parser and storage format to the element.

  There are two main contexts for datatypes. The first occurs when dealing with database application-programming interfaces (APIs) in which all elements with the same name typically contain the same type of contents. For example, all sizes contain integers. The second context occurs when the type of content varies widely from instance to instance. The frequency and flexibility of this context varies according to the software being created. For instance, size could contain the integer 6, or the word "small," or even a formula for computing the size.

• XML Data Islands
  An XML Data Island is an inline XML document within an HTML document. The XML document may hold data used within the HTML document, or it may hold data about the HTML document (author, version, and so forth).
• XML Data Source Object (DSO)
  The XML DSO allows developers to connect to XML data and supply it to the HTML page by using the data-binding functionality within Dynamic HTML.
• XML namespace
  XML namespaces are a method of creating unique XML tag names. They are based on the use of qualified names, which contain a single colon, separating the name into a namespace prefix and the local name. The prefix, which is mapped to a Universal Resource Identifier (URI), selects a namespace. The combination of the universally managed URI namespace and the local schema namespace produces names that are guaranteed to be universally unique.
• XML object model
  The XML parser exposes the XML object model, making it possible to access as objects each of the nodes within an XML tree. Through script, it is then possible to navigate and manipulate an XML tree. The XML object model tracks the World Wide Web Consortium Document Object Model.
• XML parser
  See Microsoft XML parser
• XSL (Extensible Stylesheet Language)
  XSL is a style-sheet language that defines the rules for mapping structured XML data and documents. Derived from Document Style Semantics and Specification Language (DSSSL), XSL also has roots in the Standard Generalized Markup Language (SGML) community.

  Using XSL, an element can be formatted and displayed in multiple places on a Web page, or rearranged or removed from the page. Developers can then generate a presentation structure that may be quite different from the original data structure. XSL does not replace Cascading Style Sheets (CSS); rather, it is designed to handle the new capabilities of XML that CSS cannot. Although CSS can be used to display simple XML data, CSS is not general enough to handle all of the possibilities generated by XML; the syntax of XSL can.

• XSL Control
  The XSL ActiveX Control enables output to be displayed by a Web browser. In other words, the XSL Control allows XML data to be displayed within an HTML page using an XSL style sheet.

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