XML

Submitted BY : Alsnabani Aleem 48Almaqashi Saleem 49Ameeta 50

• Structure of XML Data• Xml Querying and Transformation• Storage of XML Data• XML Applications

Abstraction .

Introduction• XML: Extensible Markup Language• Defined by the WWW Consortium (W3C)• Derived from SGML (Standard Generalized Markup

Language), but simpler to use than SGML • Documents have tags giving extra information about

sections of the document– E.g. <title> XML </title> <slide> Introduction

…</slide>• Extensible, unlike HTML

– Users can add new tags, and separately specify how the tag should be handled for display

Con…..• The ability to specify new tags, and to create nested tag

structures make XML a great way to exchange data, not just documents.– Much of the use of XML has been in data exchange applications,

not as a replacement for HTML

• Tags make data (relatively) self-documenting – E.g.

<bank> <account>

<account_number> A-101 </account_number> <branch_name> Downtown </branch_name> <balance> 500 </balance>

</account> <depositor>

<account_number> A-101 </account_number> <customer_name> Johnson </customer_name>

</depositor> </bank>

XML: Motivation• Data interchange is critical in today’s networked world

– Examples:• Banking: funds transfer• Order processing (especially inter-company orders)• Scientific data

– Chemistry: ChemML, …– Genetics: BSML (Bio-Sequence Markup

Language), …– Paper flow of information between organizations is being

replaced by electronic flow of information• Each application area has its own set of standards for

representing information• XML has become the basis for all new generation data

interchange formats

Structure of XML Data• Tag: label for a section of data• Element: section of data beginning with <tagname> and

ending with matching </tagname>• Elements must be properly nested

– Proper nesting• <account> … <balance> …. </balance>

</account> – Improper nesting

• <account> … <balance> …. </account> </balance>

– Formally: every start tag must have a unique matching end tag, that is in the context of the same parent element.

• Every document must have a single top-level element

Cont…..• Mixture of text with sub-elements is legal in XML.

– Example: <account>

This account is seldom used any more. <account_number> A-102</account_number> <branch_name> Perryridge</branch_name> <balance>400 </balance></account>

– Useful for document markup, but discouraged for data representation

Attributes• Elements can have attributes

<account acct-type = “checking” > <account_number> A-102 </account_number> <branch_name> Perryridge </branch_name> <balance> 400 </balance>

</account>• Attributes are specified by name=value pairs inside the

starting tag of an element• An element may have several attributes, but each

attribute name can only occur once<account acct-type = “checking” monthly- fee=“5”>

Complex Example of XML<States> <State> <Name>NewJersy</Name> <Number>1</Number> </State> <State> <Name>NewYork</Name> <Number>2<Number> </State> <Gov> <Location>Washington</Location> </Gov></States>

Tree Representation of XML

N e w Je rsy

N a m e

1

N u m b er

S ta te

N e w Y o rk

N a m e

2

N u m b er

S ta te

W a sh ing ton

L o ca tion

G ov

S ta tes

XML Document Schema• Database schemas constrain what information can be

stored, and the data types of stored values• XML documents are not required to have an associated

schema• However, schemas are very important for XML data

exchange– Otherwise, a site cannot automatically interpret data

received from another site• Two mechanisms for specifying XML schema

– Document Type Definition (DTD)• Widely used

– XML Schema • Newer, increasing use

Document Type Definition (DTD)• The type of an XML document can be specified using a

DTD• DTD constraints structure of XML data

– What elements can occur– What attributes can/must an element have– What subelements can/must occur inside each

element, and how many times.• DTD does not constrain data types

– All values represented as strings in XML• DTD syntax

– <!ELEMENT element (subelements-specification) >– <!ATTLIST element (attributes) >

Importance of XML• Extensible Markup Language (XML) is fast emerging

as the dominant standard for representing data on the Internet.

• Most organizations use XML as a data communication standard.

• All commercial development frameworks are XML oriented (.NET, Java).

• All modern web systems architecture is designed based on XML.

XML Querying

• XPath– An XPath expression returns a collection of element

nodes that satisfy certain patterns specified in the expression.

– The names in the XPath expression are node names in the XML document tree that are either tag (element) names or attribute names, possibly with additional qualifier conditions to further restrict the nodes that satisfy the pattern

XPath

– There are two main separators when specifying a path:

• single slash (/) and double slash (//)– A single slash before a tag specifies that the tag

must appear as a direct child of the previous (parent) tag, whereas a double slash specifies that the tag can appear as a descendant of the previous tag at any level.

– It is customary to include the file name in any XPath query allowing us to specify any local file name or path name that specifies the path.

– doc(www.company.com/info.XML)/company => COMPANY XML doc

XQuery

– XQuery uses XPath expressions, but has additional constructs.

– XQuery permits the specification of more general queries on one or more XML documents.

– The typical form of a query in XQuery is known as a FLWR expression, which stands for the four main clauses of XQuery and has the following form:

• FOR <variable bindings to individual nodes (elements)>

• LET <variable bindings to collections of nodes (elements)>

• WHERE <qualifier conditions>• RETURN <query result specification>

Storage of XML Data

• XML data can be stored in

– Non-relational data stores• Flat files

– Natural for storing XML• XML database

– Database built specifically for storing XML data, supporting DOM model and declarative querying

– Currently no commercial-grade systems

– Relational databases• Data must be translated into relational form• Advantage: mature database systems• Disadvantages: overhead of translating data and

queries

Applications of XML• XML has a variety of uses for Web, e-business, and

portable applications.• The following are some of the many applications for

which XML is useful:• Web publishing: XML allows you to create interactive

pages .• Metadata applications: XML makes it easier to

express metadata• Web searching and automating Web tasks: XML

defines the type of information contained in a document, making it easier to return useful results when searching the Web: in a portable, reusable format.

• HTML , WML . .. etc

Advantages of XML• XML is an open standard. • It is human readable and not cryptic like a machine

language.• XML processing is easy.• It can be used to integrate complex web based

systems(using XML as communication).

Conclusion

• XML is more than just a text format for describing documents. It is a mechanism for describing structured and semi-structured data, which provides access to a rich family of technologies for processing such data. Powerful abstractions like the XML Information Set open the door to processing non-textual data such as file systems, the Windows® registry, relational databases and even programming language objects using XML technologies. XML brings us one step closer to universal data access.

REFRENCES

"XML Media Types, RFC 3023“ -• http://web.archive.org/web/20110514120305/http://

diveintomark.org/archives/2004/01/08/postels-law

• ^ "XML and Semantic Web W3C Standards Timeline“

 • ^ "Extensible Markup Language (XML) 1.0 (Fifth

Edition)“

• ^ "W3C I18N FAQ: HTML, XHTML, XML and Control Codes"

Thank You !!