X

X.500
Directory access protocol. The high-level specification and interface definition for
directory access. Generally used in commercial mainframe environments.

X.509
Certificate format standard. The principal standard format definition for
certificates that are used to provide encryption and authentication.

XA
X/Open transaction interface. The X/Open organization defined standard for
communication between transaction managers and resource managers in a twophase
commit distributed transaction system.

XATM
XA Transaction Manager. A component included in MTS that allows transactions
against data stores which use the XA interface to be integrated into MTS
transactions.

XID
XA Transaction Identifier. A unique identifier for a transaction process that is
executing against an XA resource manager.

XLF
Extensible Log Format. A proposal for an XML-based Web server log format,
designed to be extensible and universal. Supported by over 50 participants from
small and large companies, universities, government, and research institutes.

XLL/XLink
Extensible Linking Language. A set of constructs for use in XML documents to
describe links between it and other resources. Uses XML syntax to create structures
that can describe both simple unidirectional hyperlinks and more sophisticated multiended
and typed links.

XMI
XML Metadata Interchange Format. A project designed to unifying XML and
related W3C specifications with several object/component modeling standards to
assist in defining, validating, and sharing document formats over the Web.

XML
Extensible Markup Language. A markup language based on SGML, and designed
to remove the limitation imposed by HTML. Allows a page to contain a definition and
execution plan for the elements, and well as their content.
XPL/XPointer
Extensible Pointer Language. A set of constructs for use in XML documents to
provide direct links to targets within the internal structure of specific elements,
character strings, and other parts of XML documents.

XSL
Extensible Style Language. An XML-based language for expressing
transformations to elements and data, and for specifying formatting within XML
documents. It describes how an instance of an object, by class, is transformed into
part of an XML document for presentation.

XT
The original version of the first IBM PC, developed by IBM, that used an 8088
processor and included a hard disk.

Xmodem
A communications protocol that allows you to transfer files between your computer
and a network with error correction.

XT keyboard
A type of keyboard used by the IBM PC which had ten function keys running in two
columns along the left-hand side of the keyboard. The current standard is called the
AT or Windows 95 keyboard. These include 12 function keys and, in the case of a
Windows 95 keyboard, a special button that's equivalent to pressing the Start button
on screen.