XML Engr. Faisal ur Rehman CE-105T Spring 2007

Definition XML-EXTENSIBLE MARKUP LANGUAGE: provides a format for describing data. Facilitates the Precise declaration of content and meaningful result across multiple platforms. XML separates Presentation from data. This separation of data from presentation enables the integration of data from diverse sources. Customer information, purchase orders, research results, bill payments, medical records, catalog data, and other information can be converted to XML.

Explanation HTML tags describes formatting while xml tag describe data like city name, temperature and barometric pressures. XML uses a set of tags to delineate elements of data. Each element encapsulates a piece of data that may be very simple or very complex. You can define an unlimited set of XML tags. For example, you might define XML tags to declare pieces of data from a purchase order, such as the price, tax, shipping address, billing address, and so on. As XML tags are adopted throughout an organization and across organizations, data from all kinds of different data stores will be easier to exchange and manipulate.

Explanation XML uses Extensible stylesheet Language (XSL) and cascading style sheets (CSS) to present data in browser. XML is a subset of SGML that is optimized for delivery over the Web. It is defined by the World Wide Web Consortium (W3C). This standardization ensures that structured data will be uniform and independent of applications or vendors.

XML vs HTML The following are a few important points to keep in mind about the relationship between XML and HTML: XML is not a replacement for HTML; in fact, XML can be considered a complement to HTML. XML and HTML have different goals: HTML is designed to display data and is focused on how data looks, while XML is designed to describe data and to focus on what data is. Like HTML, XML does not do anything. While XML tags can be used to describe the structure of an item such as a purchase order, it does not contain any code that can be used to send that purchase order, process it, or ensure that it is filled. Other people must write code to actually do these things with your XML-formatted data. Unlike HTML, XML tags are defined by the author of a schema or document and are unlimited. HTML tags are predefined; HTML authors can only use tags that are supported by the current HTML standard.

Uses of XML XML is an extremely flexible way to pass around data. The following are all examples where XML can be used: An ordinary document A structured record, such as an appointment record or purchase order Internet/intranet Web applications that move data An object with data, such as the persistent format of an object or ActiveX control A data record, such as the result set of a query Meta-content about a Web site, such as Channel Definition Format (CDF) Graphical presentation, such as an application's user interface Links between information and people on the Web C# code, which can be documented with XML Discovery documents used to locate available XML Web services

XML Advantages The following lists several advantages XML has over other formats when storing information: XML formats are text-based, making them more readable, easier to document, and sometimes easier to debug. XML documents can use much of the infrastructure already built for HTML, including the HTTP protocol and some browsers. HTTP allows XML to be transferred across firewalls. XML parsing is well defined and widely implemented, making it possible to retrieve information from XML documents in a variety of environments.

XML Advantages Applications can rely on XML parsers to do some structural validation, as well as data type checking (when schemas are used). XML is built on a Unicode foundation, making it easier to create internationalized documents. XML is not appropriate for every situation, however. XML documents tend to be more verbose than the binary formats they replace. They take up more network bandwidth and storage space, or require more processor time for compression. XML parsing can be slower than parsing highly optimized binary formats and can require more memory. However, careful application design can avoid some of these problems.

Further Info XML Resources If you are familiar with HTML, you can learn to create XML documents, requiring only that they be valid and well formed. For more information about XML, see the XML SDK and MSDN Online XML Developer Center Web site ( For more information, see the World Wide Web Consortium (W3C) Specification for XML (

XML Schema XML Schemas are documents that are used to define and validate the content and structure of XML data, just as a database schema defines and validates the tables, columns, and data types that make up a database. An XML Schema defines and describes certain types of XML data by using the XML Schema definition language (XSD). XML Schema elements (elements, attributes, types, and groups) are used to define the valid structure, valid data content, and relationships of certain types of XML data. XML Schemas can also provide default values for attributes, and elements. For more information, see the World Wide Web Consortium (W3C) Web site (

XML Schema You use an XML Schema to guarantee consistency among certain types of XML data that is shared between applications and organizations. An XML Schema can be used as a contract for data exchange between two applications. Organizations can publish schemas that describe the format of the XML their applications produce and consume. Other organizations and applications that wish to exchange data can then build their applications around these schemas so their xml messages will be understood. For example, a purchase order represented in XML can be validated with an XML Schema before it is sent between buyer and seller. This validation verifies that all of the elements (individual pieces) of data exist, are in the expected sequence, and are all of the correct data type. This ensures that the recipient of the purchase order will be able to interpret the data correctly when it is received.

Q & A Define XML, CSS, XSL and XSD. Define XML schema. Write points for XML vs HTML Write points for Advantages and Uses of XML

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