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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
(http://msdn.microsoft.com/xml/default.asp).
• For more information, see the World Wide Web
Consortium (W3C) Specification for XML
(http://www.w3.org/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 (http://www.w3.org/).
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
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Define XML, CSS, XSL and XSD.
Define XML schema.
Write points for XML vs HTML
Write points for Advantages and Uses of
XML
Lab + Assign
• VDO Lecture 10 ABS Beginner Series
• Assignment = Exercise in Register copy
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