X through Z

X.400

(n.) A message handling system standard.

X.500 standard

(n.) The set of ISO/ITU-T documents outlining the recommended information model, object classes, and attributes used by Directory Server implementation. LDAP is a lightweight version of the Directory Access Protocol (DAP) used by the X.500 standard.

Xalan

(n.) An interpreting version of XSLT.

XA protocol

(n.) A database industry standard protocol for distributed transactions.

XHTML

(extensible hypertext markup language) (n.) A reformulation of HTML 4.0 which can be extended by adding new elements and attributes. An XML look-alike for HTML defined by one of several XHTML DTDs. To use XHTML for everything would of course defeat the purpose of XML, because the idea of XML is to identify information content, and not just to tell how to display it. You can reference it in a DTD, which allows you to say, for example, that the text in an element can contain <em> and <b> tags rather than being limited to plain text.

XLink

(n.) The part of the XLL specification that is concerned with specifying links between documents.

XLL

(n.) The XML Link Language specification, consisting of XLink and XPointer.

XML

(extensible markup language) (n.) A flexible programming language developed by the World Wide Web Consortium (W3C) to create common information formats and to share both the format and the data on the web, intranets, and elsewhere. This markup language allows you to define the tags (markup) needed to identify the content, data, and text in XML documents. It differs from HTML, the markup language most often used to present information on the Internet. HTML has fixed tags that deal mainly with style or presentation. An XML document must undergo a transformation into a language with style tags under the control of a style sheet before it can be presented by a browser or other presentation mechanism. Two types of style sheets used with XML are CSS and XSL. Typically, XML is transformed into HTML for presentation. Although tags can be defined as needed in the generation of an XML document, a document type definition (DTD) can be used to define the elements allowed in a particular type of document. A document can be compared by using the rules in the DTD to determine its validity and to locate particular elements in the document. A Web services application's J2EE deployment descriptors are expressed in XML with schemas defining allowed elements. Programs for processing XML documents use SAX or DOM APIs. The Calendar Server uses XML and XSL to generate the Calendar Express user interface.

XML namespace

(n.) A standard that allows you to specify a unique label to the set of element names defined by a DTD (document type definition). A document using that DTD can be included in any other document without having a conflict between element names. The elements defined in the DTD are then uniquely identified so that, for example, the parser can determine when an element should be interpreted according to your DTD and not according to that of another document type definition.

XML registry

See registry.

XML schema

(n.) The W3C specification for defining the structure, content, and semantics of XML documents.

XPath

(n.) An addressing mechanism for identifying the parts of an XML document.

XPointer

(n.) The part of the XLL specification that is concerned with identifying sections of documents so that they can be referenced in links or included in other documents.

XSL

(extensible style language) (n.) A language used to create style sheets for XML, similar to cascading style sheets (CSS) that are used for HTML. In XML, content and presentation are separate. XML tags do not indicate how they should be displayed. An XML document has to be formatted before it can be read. The XSL standard lets you do the following:

• Specify an addressing mechanism, so that you can identify the parts of an XML document that a transformation applies to (XPath).

• Specify tag conversions, so that you can convert XML data into different formats (XSLT).

• Specify display characteristics, such page sizes, margins, and font heights and widths, as well as the flow objects on each page. Information fills in one area of a page and then automatically flows to the next object when that area fills up. That allows you to wrap text around pictures, for example, or to continue a newsletter article on a different page (XSL-FO).

XSL-FO

(n.) A subcomponent of XSL used for describing font sizes, page layouts, and how information flows from one page to another.

XSLT

(extensible style language transformation) (n.) The language used by XML style sheets to transfer one form of an XML document to another XML form. This transition is extremely useful in e-commerce and e-business, as the transition serves as a common denominator across many different platforms and varying XML document coding. The target document often has presentation-related tags dictating how it will be rendered by a browser or other presentation mechanism. XSLT was formerly a part of XSL, which also included a tag language of style flow objects.

XSLTC

(n.) A compiling version of XSLT.

Zulu time

(n.) A military designation for GMT and UTC (coordinated universal time).