As I have said in the other article XML is the abbreviated form of Extensible Markup Language and it describes a class of data objects called XML documents and partially describes the behaviour of computer programs which process them. Once knew the meaning and how it works, let’s start listing some of its goals:

XML shall be straightforwardly usable over the Internet.
1. XML shall support a wide variety of applications.
2. XML shall be compatible with SGML.
3. It shall be easy to write programs which process XML documents.
4. The number of optional features in XML is to be kept to the absolute minimum, ideally zero.
5. XML documents should be human-legible and reasonably clear.
6. The XML design should be prepared quickly.
7. The design of XML shall be formal and concise.
8. XML documents shall be easy to create.
9. Terseness in XML markup is of minimal importance.

The terminology used to describe XML documents is defined in the body of this specification. The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when EMPHASIZED, are to be interpreted as described in RFC 2119. For example, MUST means that the definition is an absolute requirement of the specification or MUST NOT/ SHALL NOT, mean that the definition is an absolute prohibition of the specification. I list some of the terminology used:

• Error: A violation of the rules of this specification; results are undefined. Unless otherwise specified, failure to observe a prescription of this specification indicated by one of the keywords MUST, REQUIRED, MUST NOT, SHALL and SHALL NOT is an error.

• At user option: Conforming software MAY or MUST (depending on the modal verb in the sentence) behave as described; if it does, it MUST provide users a means to enable or disable the behavior described.

• Well-formedness constraint: A rule which applies to all well-formed XML documents. Violations of well-formedness constraints are fatal errors.

• For compatibility: Definition: Marks a sentence describing a feature of XML included solely to ensure that XML remains compatible with SGML.

The list could continue, but i will just finish by saying that the future is already among us and we had better get ready for the IT advances that are to come.

 

Sources:

• http://www.ietf.org/rfc/rfc2119.txt
• http://www.w3.org/TR/xml11/#sec-xml11