XML : eXtensible Markup Language :: About XML Document

• Structure of XML Document?
• Steps for Building XML Document
• Rules governing the elements
• Data Vs Markup
• Comments in XML
• Character Data [ CDATA vs PCDATA]
• Entities
• XML Document Scope and Application

• Composed of sets of “entities” identified by unique names.
• Begin with a “root” or document entity.
• SAMPLE of XML Document.

• State an XML declaration
• Mention a root element
• Then Define the XML code

XML document consists of data and the markup that describes the data.

• Rules followed while using comments
• “- -” should not be included within the text of the comment
• A comment should never be placed within a tag
• A comment should never be placed inside an entity declaration or before the XML declaration.
• Comments can be used to comment tag sets
• Comments cannot be nested

• The text between the start and end tags is defined as “character data”.
• Character data may be any legal (Unicode) character with the exception of “<“.

• Storage units of XML.
• Used within a document to avoid typing long pieces of text repeatedly.
• Some of the predefined entities representing characters

Type of Entity

• General Entity
• Parameter Entity

1. General Entity

Entities that can appear anywhere in an XML document

Example for general Entity

Type of General Entity

• Internal : Exist in the document where they were declared
• External : Refer to a storage unit outside the document

<!ENTITY ADDRESS "text that is to be represented by an entity">

2. Parameter Entity

• Parameter entity is used when entities and entity references are required to appear only in the DTD.
• Parameter entities, either internal or external, are only used within the DTD.
• It includes “%” specifier.

Example for Parameter Entity

<! ENTITY % ADDRESS "text that is to be represented by an entity">

Pre-defined Entity

• Valuable both to the Internet and large corporate intranet environments.
• Provides interoperability using a flexible, open, standards-based format.
• Applications can be built more quickly.
• Easier to maintain
• Can easily provide multiple views of the structured data using different style sheets
• Examples for the use of XML: Chemical Markup Language [ CML ]