Extensible markup language takes the best features of standard generalized markup language and combines it with some features of hyper text mark up language and adds rest of the features from successful applications of both. Extensible markup language takes its major frame work from standard generalized mark up language.
It is commonly called subset of standard generalized mark up language but in technical terms it is an application profile of standard generalized markup language where as hyper text mark up language uses standard generalized markup language and is an application of standard generalized markup language, extensible markup language is just standard generalized markup language on a very small scale. Extensible markup language inherits the use of web address from hyper text mark up language.
Extensible markup language also adds a list of features that make it far more suitable than either standard generalized markup language or html for use on web. Html appears to have no document type definition. There is an implied document type definition hard coded into web browsers. Standard generalized markup language has a limitless number of document type definitions on the other hand, but there is only one for each type of document. Extensible markup language enables user to leave the document type definition all together combines multiple fragments of either extensible markup language instance or separates document type definitions into one compound instance. Extensible markup language’s powerful linking mechanism slows user to link to material without requiring the link target to physically present in the object that is extensible markup language opens possibilities fro linking together things like material to which accessing compact disc read only memory, library catalogues, the result of database queries is not required.
Further it allows user to store the links separately from the object they link. Apart from linking extensible markup language introduces a very superior way of including link targets in the current instance. This opens a new doorway towards composite documents that is documents composed of fragments of other documents that are automatically assembled to form what is displayed at that particular moment. Both hypertext mark up language and standard generalized markup language sing foreign characters whereas xml is based on Unicode and requires all xml software to support Unicode as well, Unicode enables xml to handle not just western accented characters but also Asian languages. Traditional computer storage allows one byte of storage for each character. However this only works out to allowing two hundred and fifty six choices of characters. The first one hundred and twenty eight characters are typically the same and the last hundred and twenty eight characters vary based on the character set. Unicode is a way to allow a computer to keep two bytes per character.