XML little guide
On the surface, XML looks like HTML. Both are derived from the Standard
Generalized Markup Language (SGML). Tools that generate HTML can often be reused
to generate XML.
Both HTML and XML use <, >, and & to create element and attribute
structures. While HTML browsers accept or ignore mangled markup language, XML
parsers, and applications built on those parsers, are less forgiving. Errors in
XML syntax halt document processing, and users or applications receive error
messages.
-
XML tags and attributes are case sensitive. This
means that <NODE> <and <Node> are seen as a completely different
tags.
- All tags must closed. All open
tag need a closing tag. You can specificy unique tags using / character this
way: <BR/>
- Elements in XML documents cannot overlap. If the start
tag for an element appears within another element, it must end within the same
containing element.
- All attribute values must be quoted, whether or not they
contain spaces. You still have the option of single - or double - quotes
- You cannot use the characters <, >, or
& within the text of your documents
. Use the built-in entities
<,
>, or &
XML has several key advantages:
- XML allows developers to create their own labeled structures for storing
information.
- XML parsing is well-defined and widely-implemented, making it possible to
retrieve information from XML documents in a variety of environments.
- Applications can rely on XML parsers to do some structural validation, as
well as data type checking (when schemas are used).
- XML formats are text-based, making them more readable, easier to document.
- XML documents can use much of the infrastructure
already built for HTML, including the HTTP protocol and some
browsers.