Glossary

Active Server Pages

See [ASP.]

ActivePerl

Popular, well-supported Perl distribution available for a number of platforms. Includes the Perl Package Manager (PPM) tool that simplifies Perl module installation and removal. This is the recommended Perl distribution if you are running on a Microsoft Windows-based platform. A small company named ActiveState originally developed the ActivePerl distribution. Their web site (and additional Perl development tools) can be found at http://www. activestate .com.

American Standard Code for Information Interchange

See [ASCII.]

API (Application Programming Interface)

An interface built into a software package that enables other applications to use the package. For example, when you use a Perl module, you are interacting with the module through an API.

Application Programming Interface

See [API.]

ASCII (American Standard Code for Information Interchange)

Standard defined by the American National Standards Institute (ANSI) that defines a coded character set based on 7-bit coded characters . Each character is assigned a unique number ranging from 0 to 127. The characters assigned to values 0 “31 are non-printing control characters, and values 32 “127 are assigned to letters , numbers , and other symbols.

ASP (Active Server Pages)

Originally developed by the Microsoft Corporation for its own web servers; however, it is now available for a number of web servers. Because the ASP engine is integrated into the web server, it doesn't require another process. ASP enables the developer to merge source code within HTML pages. A Perl module named Apache::ASP supports ASP with the mod_perl module.

ATTLIST

The keyword used in DTDs to initiate the declaration of one or more attributes for an element.

Attribute

An XML parameter that describes data associated with an element. Attributes take name =value format. For example, to declare an attribute for an XML element, you use the following format: <name ssn="123-45-6789">Mark Riehl</name> . In this case, the <name> element has one attribute named ssn and the value of the attribute is " 123-45-6789 ".

Cascading Style Sheet

See [CSS.]

CDATA

An XML keyword that describes a block of data that may legally contain XML reserved characters (for example, < or > ) within an XML document. Usually, the reserved characters are replaced with the corresponding entity references. However, CDATA sections are useful when encapsulating large blocks of data inside an XML document. For example, let's say you are encapsulating an HTML document inside of an XML document. By using a CDATA section, you won't need to replace all the reserved characters with the corresponding entity references.

CGI (Common Gateway Interface)

An interface that enables external programs to interact with a web server. Static web pages are basically text files that don't change. CGI scripts execute in real time, allowing you to dynamically generate web content. For example, it's very easy to build a CGI script that builds a web form, collects data from a user , queries a database, and builds a web page containing the results. CGI scripts are frequently written in Perl.

Character data

The text in an XML document excluding markup. For example, the following XML element: <name>Mark Riehl</name> contains the character data " Mark Riehl ".

Character reference

A method of including non-printable Unicode characters in an XML document. These characters could be letters from a foreign language. The character reference contains the number of a particular Unicode character.

Comma Separated Value

See [CSV.]

Comment

Added to XML documents by using the following notation:

 <!Comment text here. > 

Note that it is a good idea to add comments throughout your XML documents. Depending on the XML parser used, you may or may not have access to the comments after parsing.

Common Gateway Interface

See [CGI.]

Comprehensive Perl Archive Network

See [CPAN.]

CPAN (Comprehensive Perl Archive Network)

A mirrored web site that provides a wealth of Perl information. For example, it provides links to Perl modules, documentation, mailing lists, and Frequently Asked Questions (FAQs). Whenever you're looking for any Perl information, this is a great place to start. CPAN is at http://www.cpan.org.

CSS (Cascading Style Sheet)

A simple non-XML language that was developed to support adding styles (for example, fonts, colors, and so forth) to web documents. It was originally developed to work with HTML, however it also works with XML. Support for CSS varies widely among browsers.

CSV (Comma Separated Value)

A file that contains commas as delimiters between fields. An example of a CSV file is a database table or a spreadsheet that has been exported to a text file. In the exported text file, commas are used to separate the columns , and new lines are used to separate the rows.

Database Interface

See [DBI.]

Database Management System

See [DBMS.]

DBI (Database Interface)

The Perl DBI is a widely used Perl module that provides transparent access to multiple database servers using a consistent API. The DBI module handles all the underlying differences between database servers. Some of the supported databases include Informix, Ingres, Microsoft SQL Server, mSQL, MySQL, Oracle, PostgreSQL, and all ODBC-compliant database servers. The Perl DBI homepage can be found at http://dbi.perl.org/.

DBMS (Database Management System)

Typically describes a system that manages large amounts of data, optimized for easy and fast retrieval.

Document Object Model

See [DOM.]

Document Type Definition

See [DTD.]

DOM (Document Object Model)

A platform and language independent standard that enables programs to access and modify the contents of a document. DOM can support HTML and XML documents and is considered to be a tree-based parser because it builds a tree of the input document in memory. Because it builds the tree in memory, DOM parsers are not recommended for parsing large documents. DOM-based XML parsers are written in a number of languages, including Java, C/C++, and Perl.

DTD (Document Type Definition)

A non-XML file that defines the structure and content of an XML document.

Element

An XML element is the smallest building block of an XML document. Typically, an XML element is made up of a start tag, element content, and an end tag. A typical element has the following format: <employee>James Kennedy</employee> . In this example, <employee> is the start tag, " James Kennedy " is the element content, and </employee> is the end tag.

ELEMENT Declaration

The declaration of an XML element appears in a DTD. The format for the declaration is: <!ELEMENT name (content)> . Remember, the content of an element could be text or other elements.

Empty element

An XML element that doesn't have any content is called an empty element. An empty XML element is represented by <employee></employee> or the shorthand notation <employee/> .

End tag

An end tag is the closing tag required to define an XML element. For example, in the element <city>Ocala</city> , the tag </city> is the end tag of the element.

ENTITIES

An attribute type that can hold a list of ENTITY names (see ENTITY) separated by spaces. For example, multiple ENTITIES can be defined in a DTD using the following format:

 <!ATTLIST annual_report  charts ENTITIES #IMPLIED>  <!ENTITY sales_chart1 SYSTEM  "sales1.jpg">  <!ENTITY sales_chart3 SYSTEM  "sales2.jpg">  <!ENTITY sales_chart3 SYSTEM  "sales3.jpg"> 

In an XML document, the ENTITIES attribute would be used as follows :

 <annual_report charts=  "sales_chart1 sales_chart2  sales_chart3"> 

ENTITY

An attribute type that can be set to the name of an entity that is defined elsewhere in the DTD. An ENTITY (for example, in this case, a JPG version of a chart) can be defined in a DTD using the following format:

 <!ATTLIST annual_report  sales_chart ENTITY #IMPLIED>  <!ENTITY sales_chart SYSTEM  "sales1.jpg"> 

Throughout the XML document, we can refer to " sales1.jpg " by using the attribute sales_chart . For example, we could use " sales_chart " as an attribute type in the following XML element declaration:

 <annual_report  graphic="sales_chart"> 

Entity reference

A markup construct used to replace a reserved character (for example, < , > , or "'") from appearing inside character data within an element. For example, the following string " Mark's car " would appear inside an XML element as <name>Mark&apos;s car</name> .

Enumerated List

A list that contains a list of valid values. An XML attribute can be declared to specify that the only valid value must be selected from a list. For example, let's say that we're declaring a day attribute of the <sales_report> element in the DTD: <!ATTLIST sales_report day (Monday Tuesday Wednesday Thursday Friday Saturday Sunday) . This declaration tells us that the only valid values for day are the names of the days of the week ” Monday through Sunday.

Event-based XML parser

One of the major paradigms used in XML parsing. An event-based XML parser calls predefined subroutines when it encounters a particular construct inside the XML document. For example, a start handler would be called each time the parser encounters a new start tag.

eXtensible HyperText Markup Language

See [XHTML.]

eXtensible Markup Language

See [XML.]

eXtensible Stylesheet Language

See [XSL.]

eXtensible Stylesheet Language Transformation

See [XSLT.]

File Transfer Protocol

See [FTP.]

FIXED

A DTD keyword used in the declaration of an attribute. Use of the FIXED keyword means that the attribute has been assigned a constant value.

FTP (File Transfer Protocol)

A TCP-based protocol used to transfer files between two machines. The full description of FTP can be found in Request for Comment (RFC) 959.

HTML (HyperText Markup Language)

The de facto language standard published by the W3C that is used for publishing hypertext on the World Wide Web. HTML is a descendent of SGML. Additional HTML information can be found at http://www.w3.org/MarkUp/.

HTTP (HyperText Transfer Protocol)

An Application layer protocol to transfer information to and from web servers. HTTP is a TCP-based, stateless protocol. The full description of HTTP can be found in RFC 2616 and additional information can be found at http://www.w3.org/Protocols/ .

HyperText Markup Language

See [HTML.]

HyperText Transfer Protocol

See [HTTP.]

ID

A keyword that is used in a DTD attribute. The ID keyword indicates that the value of the attribute is unique within the XML document.

IDREF

An attribute type that contains the ID value of another element in the XML document. A common use of an IDREF attribute is to establish a hierarchy between elements.

IDREFS

An attribute type that contains whitespace-separated ID values.

See also [IDREF.]

IMPLIED

A DTD keyword used within an <!ATTLIST> tag to indicate that an attribute is optional.

International Organization for Standardization

See [ISO.]

International Standard Book Number

See [ISBN.]

ISBN (International Standard Book Number)

A unique, machine readable identification number assigned to books (i.e., the publishing equivalent of a Social Security number). For additional information please see http://www.isbn.org.

ISO (International Organization for Standardization)

A series of national standards organizations from 140 different countries . The goal is non-government development of standards to facilitate international commerce.

Java

A programming language developed at Sun Microsystems by James Gosling and Bill Joy. Java was designed from the beginning to be platform-independent.

JavaServer Pages

See [JSP.]

JSP (JavaServer Pages)

A Java-based web technology that delivers dynamic content to a client. JSPs consist of markup text (usually HTML or XML) combined with Java. The client can be a web browser, and the data is frequently HTML or XML.

Markup delimiter

A group of characters used to delimit text documents. In XML markup, characters are used to delimit the start and end of an element. Some markup delimiters are '<<', '>>', '//>', and '</</'. Typically, they're used to delimit elements such as the one shown here: <model>Chevrolet Corvette</model> .

mod_perl

An Apache web server and Perl integration project that links the Perl runtime library into the web server and provides an object-oriented Perl interface to the C API of the web server. The major reason for using mod_perl is that it increases the performance of a web server. Because the Perl runtime library is already linked into the web server, there is no need to launch a new Perl process to run a CGI script.

NMTOKEN

A DTD attribute type. The name NMTOKEN stands for name token and has many of the same characteristics as an XML name. For example, an NMTOKEN must be made up of the same characters as an XML name ( alphanumeric or the following punctuation marks _, -, ., and :). Unlike an XML name, an NMTOKEN can have a number or a punctuation mark as the first character. An NMTOKEN can be used to bound input data. For example, let's say that you have an <employee> element that has an employee number attribute declared as:

 <!ATTLIST employee employee_ number NMTOKEN #REQUIRED> 

By using the NMTOKEN attribute type, it will only be valid for valid NMTOKEN s. So, it would be valid for an employee number such as "123", and invalid for an attribute value of "1 23" (invalid because of the whitespace). However, an NMTOKEN won't prevent an attribute value containing a string, such as " Mark ".

PCDATA

A DTD keyword used to describe parsed character data. The term PCDATA is usually used to declare the contents of an element. Note that an element declared to contain PCDATA may contain entity references; however, it cannot contain any tags or child elements.

PDF (Portable Document Format)

A document format that was developed by Adobe as a means of transferring documents between different platforms. Additional information can be found at http://www.adobe.com.

Perl (Practical Extraction and Reporting Language)

A high-level programming language originally developed by Larry Wall. Perl is ideally suited for such tasks as text manipulation, system management, database access, networking, and web programming.

Perl module

A self-contained piece of Perl code that performs a particular task. A module can be used by a Perl program or by other modules. Perl modules are freely available to perform just about any imaginable task. The best place to start looking for a module is CPAN, http://search.cpan.org.

Perl Package Manager

See [PPM.]

Personal Home Page

See [PHP.]

PHP (Personal Home Page)

A programming language that is similar to Perl. Unlike Perl, PHP uses an interpreter that is embedded in the web server itself. Similar to ASP, PHP supports embedding server-side programming code in HTML pages. PHP is supported by the Apache web server. Additional information on PHP can be found at http://www.php.net/.

PI (Processing Instruction)

Markup that appears in an XML document that is used to pass instructions to the XML processor. All PIs start with <? and end with ?> . The only restriction is that you cannot use <?xml?> or <?XML?> . Note that because PIs are instructions being sent to the XML processor, they are processor-dependent and are not specified by the XML standard. A commonly used PI is <?xml-stylesheet?> .

POP3 (Post Office Protocol version 3)

A simple protocol designed to retrieve electronic mail. Additional information on POP3 can be found in RFC 1939.

Portable Document Format

See [PDF.]

Post Office Protocol version 3

See [POP3.]

PPM (Perl Package Manager)

A tool developed by ActiveState that assists in the task of Perl module management. For example, allowing a user to install, remove, or update modules from a number of Perl module repositories. Additional information is available at http://www.activestate.com.

Practical Extraction and Reporting Language

See [Perl.]

Processing Instruction

See [PI.]

Remote Procedure Call

See [RPC.]

REQUIRED keyword

A DTD keyword used inside the declaration of an attribute. If the REQUIRED keyword is used, then the attribute must be present in a valid XML document.

RTF (Rich Text Format)

A file format originally developed by the Microsoft Corporation. An RTF file is an ASCII file that contains special format commands to define presentation characteristics, such as fonts and margin sizes.

Rich Text Format

See [RTF.]

Root element

The single XML element per XML document that contains all other elements. In an XML document, this is always the first element encountered .

RPC (Remote Procedure Call)

A type of network programming where a client actually calls functions that reside in a server. This is a different approach to client-server programming. Typically, a client connects to a server using a socket, the client sends a request, and the server processes the request and then sends back a reply.

SAX (Simple API for XML)

An event-based XML parsing API. The user defines a series of event handler subroutines that are called when the parser encounters a particular construct. For example, a start event handler will be called each time the parser encounters the start of an element. Unlike the DOM-based parsers, SAX is ideal for parsing large XML documents because it doesn't build a tree of the XML document in memory.

SAX2 (Simple API for XML version 2)

Version 2 of the SAX standard. Includes bug fixes and additional functionality (for example, better namespace support than the original SAX version). The official SAX2 web site is at http://www.saxproject.org/ .

Scalable Vector Graphics

See [SVG.]

Schematron

An XML-based language that uses XPath to query XML documents. Additional information is available at http://www.ascc.net/xml/resource/schematron/ .

SGML (Standard Generalized Markup Language)

A language developed to support electronic publishing of documents. SGML is the predecessor to XML.

Simple API for XML

See [SAX.]

Simple API for XML version 2

See [SAX2.]

Simple Mail Transfer Protocol

See [SMTP.]

Simple Object Access Protocol

See [SOAP.]

SMTP (Simple Mail Transfer Protocol)

A protocol designed to deliver electronic mail. Additional information can be found in RFC 821.

SOAP (Simple Object Access Protocol)

SOAP is a lightweight protocol designed to exchange structured information in a distributed environment. XML is used as the message format, and SOAP messages can be distributed by a number of different underlying protocols. Additional information can be found at http://www.w3.org/TR/2001/WD-soap12-part0-20011217/ .

SQL (Structured Query Language)

An ANSI standard language that was developed to interact with databases. SQL enables you to create, destroy, and update database tables.

Standalone

An optional attribute in the XML declaration. The standalone attribute indicates if an XML document has an internal DTD (standalone = "yes") or if the DTD is in an external document (standalone = "no").

Standard Generalized Markup Language

See [SGML.]

Start tag

An opening tag in the declaration of an XML element. In the following declaration of an XML element <nickname>The Chief</ nickname> , the first tag <nickname> is the start tag.

Structured Query Language

See [SQL.]

SVG (Scalable Vector Graphics)

A language used to describe two-dimensional graphics in XML. Currently, three types of graphic objects are supported: vector graphics, images, and text. SVG is a W3C-developed standard and additional information can be found at http://www.w3.org/TR/SVG/.

UDDI (Universal Description Discovery and Integration)

An architecture that provides integration with web services. UDDI contains specifications describing services and discovery of those services. It supports multiple platforms because it is based on W3C standards such as SOAP and XML. Additional information on UDDI can be found at http://www.uddi.org/.

Unicode

A universal character-encoding standard that represents text for computer processing. Unicode provides a method of encoding languages that use characters outside of the standard ASCII character set. Additional information on Unicode can be found at http://www.unicode.org.

Universal Description Discovery and Integration

See [UDDI.]

W3C (World Wide Web Consortium)

A group comprised of over 500 member organizations dedicated to promoting interoperability of web-based standards. The W3C is responsible for over 40 technical specifications that basically form the infrastructure of the World Wide Web. Additional information on the W3C is available at http://www.w3c.org.

Web Services Description Language

See [WSDL.]

Wireless Markup Language

See [WML.]

WML (Wireless Markup Language)

An optimized language used for specifying presentation and user interaction on particular devices, such as mobile phones and wireless PDAs. Basically, WML provides a framework for supporting web clients that don't have access to the full suite of XHTML features due to physical constraints (for example, display size , bandwidth).

World Wide Web Consortium

See [W3C.]

WSDL (Web Services Description Language)

An XML format describing network services. These services are offered on the web and accessed using SOAP. For example, a network service could offer stock quotes, taking a stock symbol as input and returning the current stock price. For additional information on WSDL, please see http://www.w3.org/TR/wsdl.

XHTML (eXtensible Hypertext Markup Language)

A major change to HTML that brings the stricter formatting rules found in XML to HTML. For example, while some browsers would display HTML that was missing end tags, all opening tags in XHTML must have a corresponding end tag. It will also enable developers to deliver web pages to a number of new devices, such as cellular phones. Additional information on XHTML can be found at http://www.w3.org/TR/xhtml1/.

XLink (XML Linking Language)

Specifies a language to support linking (similar to HTML hyperlinks ) in XML. For additional information, see http://www.w3.org/XML/Linking.

XML (eXtensible Markup Language)

A language defined by the W3C to facilitate distribution of information on the World Wide Web. Additional information can be found at http://www.w3.org/XML/.

XML Remote Procedure Call

See [XML-RPC.]

XML-RPC (XML Remote Procedure Call)

A specification and implementation that defines remote procedure calling. The transport mechanism is HTTP and XML is the encoding scheme. Additional information can be found at http://www.xmlrpc.com/.

XML Schema

An XML-based standard that describes the content and structure of an XML document. At a high level, it performs the same task as a DTD (that is, it can be used to validate an XML document); however, XML Schemas provide more options when it comes to specifying data types and number of element occurrences. Additional information can be found at http://www.w3.org/XML/Schema.

XPath

A language that enables you to address and access specific parts of an XML document. It was originally designed for use by XSLT and XPointer. Additional information can be found at http://www.w3.org/TR/xpath .

XPointer (XML Pointer Language)

Non-XML syntax based on XPath that supports addressing the internal structures of XML documents. Additional information can be found at http://www.w3.org/TR/xptr/.

XSL (eXtensible Stylesheet Language)

A language used to write XML output templates. XSL data can be transformed into XML, HTML, WML, and any other plain text format through these templates. The process of transforming an XML document via an XSL stylesheet is called XSLT (XSL Transformation).

XSLT (eXtensible Stylesheet Language Transformation)

A language for transforming XML documents into other XML documents. Can be used as part of XSL or independently of XSL. Additional information can be found at http://www.w3.org/TR/xslt.

XSLT Stylesheet

An XML document that contains templates or rules used by an XSLT processor to transform an XML document. XSLT stylesheets can be used to convert XML documents to other formats (for example, HTML or CSV) and into filtered XML documents.