niit pre xml

8/4/2019 Niit Pre XML

1/19


2/19

XML was designed to transport and storedata.HTML was designed to display data.


3/19

XML stands for Extensible Markup Language.XML is a markup language much like HTML.

XML was designed to carry data, not to display data.

XML tags are not predefined. You must define your owntags.

XML is designed to be self-descriptive.

XML is a W3C Recommendation.


4/19

XML and HTML were designed

with different goalsXML was designed to transport and store

data, with focus onwhat data is.

HTML was designed to display data, with

focus on how data

looks.HTML is about displaying information, while XML

is about carrying information. XML is not a

replacement for HTML.


5/19

Maybe it is a little hard to understand, but XML does not DO anything.

XML was created to structure, store, and transport information.

XML is Just Plain Text

XML is nothing special. It is just plain text. Software that can handle plain textcan also handle XML.

With XML You Invent Your Own Tags

The tags in the example above (like and ) are not defined in anyXML standard. These tags are "invented" by the author of the XML document

That is because the XML language has no predefined tags.


6/19

XML is a complement to HTMLIt is important to understand that XML is not a replacement forHTML.

In most web applications, XML is used to transport data, whileHTML is used to format and display the data.

EG:- XML is a software- and hardware-independent tool forcarrying information.


7/19

Clean Semantics -Any query languagefor XML must be able to express simple queries

simply. A good XML query language should be

usable by novice web-users, not just databaseexperts.

SELECT expr

FROM path

WHERE condOne possibility for a cleansemantics is to base the query language upon

the SQL select-from-wherestatement.


8/19

Path Expressions Since XML elements often contain childelements, the query language shouldsupport "path expressions," which allow the

writer easy access to nested elements.


9/19

Ability to Return an XMLDocumentThe standard behavior of most query languages is

to return a set of elements of some type.

For an XML query language the returned valueshould be an XML document


10/19

Ability to Query and Return XMLTags and Attributes -An XML data element contains data, a tag, and

optionally, attributes. It is imperative that an XML

query language be able to query the element tagsand attributes as well as the data.


11/19

Intelligent Type Coercion Since both textual and numeric data are

represented as strings in XML, the query language

should be intelligent enough in comparisonoperations to determine whether a stringcomparison is intended or if a coercion isrequired.


12/19

Handle Unexpected Data Data in XML does not have to conform to a fully-

structured DTD. Therefore, it is critical that an XML

query language "do the right thing" in the face ofunexpected data as much as possible.


13/19

Allow Queries When the DTD IsNot Fully Known It may often be the case with XML that the query

writer understands a part of the DTD, but not in itsentirety. The query language needs to support

wildcards in the path expressions to allow thequery writer to "skip past" parts of the documentstructure of which he or she is not aware.


14/19

Return Unnamed Attributes In restructuring information it is often useful to

express things like "return all child elements," or

"return all child elements except this one." An XMLquery language should support queries that returnelements even when their tags are unknown


15/19

Return Trees Instead of Sets-Although query languages usually return sets, when

restructuring an XML document it is likely that the user

will want to have the query return a more nestedstructure.


16/19

Preserve Order SGML documents have an implicit order, and XML

documents do as well. It is important for an XML

query language to be able to optionally guaranteethat the order of returned results is the same as in

the original document.


17/19

It is as easy as HTML.

XML is fully compatible with applications likeJAVA, and it can be combined with anyapplication which is capable of processing XML

irrespective of the platform it is being used on. XML is an extremely portable language to the

extent that it can be used on large networks withmultiple platforms like the internet, and it can be

used on handhelds or palmtops or PDAs. XML is an extendable language, meaning that

you can create your own tags, or use the tagswhich have already been created


18/19

It is a platform independent language

It can be deployed on any network if it is amicablefor usage with the application in use

If the application can work along with XML, thenXML can work on any platform and has noboundaries

It is also vendor independent and systemindependent. While data is being exchanged usingXML, there will be no loss of data even betweensystems that use totally different formats.


19/19

niit pre xml

Documents