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Introduction

XML provides a manner in which meta-data - data about information - can be represented in a structured format. Being a text based language, XML is very easy for a human to read and understand the data and structure.

Research

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XML and Markup Languages

Being a markup language based on SGML (Standard Generalized Markup Language), extensible markup language (XML) provides a mechanism to identify and present structured information. Unlike hypertext markup language (HTML), XML does not define tag semantics. For example, in HTML, <h2> is always a first level heading and <br> means a break in the representation of displayed information. Instead, XML is actually a meta-language for describing markup languages, providing a facility to define tags and the structural relationships between them. There is therefore no predefined tag set or semantics. Instead, all semantics of an XML document are defined by applications that process them or by stylesheets.

XML Goals

• Provide a common communications structure for media-independent communications across systems
• Allow industries to define platform-independent protocols for data exchange
• Allow for the flexible display of information
• Keep the number of optional XML features to a minimum so as to reduce the potential for compatibility problems

XML Structure and Processing of Information

XML uses start and end tags such as <zone> and </zone> to mark up information. Information marked by tags is referred to as an element. Name-value pairs called attributes may further define elements. For example, zone="postal code" indicates that a zone being defined in the XML data structure is a postal code versus any other type of zone, such as a city zone.

XML must be parsed into usable information. An XML parser will

XML makes use of something called a document type definition (DTD), which identifies markup data delineated (by paragraphs, topic headings, etc.) and how each and how they are to be processed. A XML DTD reader at the receiving end of an XML message will be able to process the data and display the information as intended. XML is used to transport data in a text format. In order to display information to the user interface, XML data must be converted into some other format such as scalable vector graphics (SVG).

Scalable Vector Graphics

Scalable Vector Graphics (SVG) is a language for describing two-dimensional graphics in XML, which supports vector graph shapes (straight lines and curves), images, and text. In addition to being a web-based standard for graphics display, SVG is also an efficient at displaying information. SVG is a more efficient approach than bitmap formats such as GIF or JPEG, which must contain information on every single pixel needed to display an image, making files big, slow, and static, with no interactivity.

Extended Links and Extended Pointers

Extended Links (XLink) allow for the expression of relationships between two or more resources. Extended Pointers (XPointer) provide a method of locating resources within a body of data, without the need for that resource being identified with an ID attribute.