XMLAn Introduction

1
XML-An Introduction

• The eXtensible Markup Language (XML) created by
  the World Wide Web Consortium (W3C) in 1996 to
  address limitations of HTML
• XML a language similar to HTML, but more
  extensible
• Supports user defined tags that allow both data
  and metadata (i.e. data about data) to be
• stored in a single document
• At the same time, presentation aspects remain
  decoupled from data representation

2
A Brief History

• HTML and XML are like children of the same
  parent, Standardized General Markup Language
  (SGML).
• SGML, made a standard of the ISO in 1986
• SGML originated in IBM, which wanted a
  means of publishing document content in
  different ways.
• The result of the standards process A rich
  document markup language, allowing authors to
  separate logical content from its presentation
• SGML, a series of commands understood by another
  program.

3
Why Another Markup Language?

• The question to be asked is What's Wrong With
  SGML or HTML?
• SGML is very large, powerful and COMPLEX.
• SGML used in industry, for commercial purposes
  for over a decade.
• SGML too complex to program for a Web environment

4
Why Another Markup Language? contd

• HTML can be thought of as a small application of
  the SGML used on the web
• HTML defines a very simple class of report-style
  documents, with section headings,paragraphs,
  lists, tables, and illustrations etc.
• It was the first computer language that could be
  understood and used by the masses. It gave the
  Web to the common person.
• HTML is said to be static, one can do limited
  things with HTML

5
Advantages of XML over HTML
6
XML

• XML allows users to
• Bring multiple files together to form compound
  documents
• Identify where illustrations are to be
  incorporated into text files, and the format used
  to encode each illustration
• Provide processing control information to
  supporting programs, such as document validators
  and browsers
• Add editorial comments to a file

7
XML Components

• XML is based on the concept of documents composed
  of a series of entities
• Each entity can contain one or more logical
  elements
• Each of these elements can have certain
  attributes (properties) that describe the way in
  which it is to be processed

8
XML Few Important Points

• Tag names are case sensitive
• Every opening tag must have a corresponding
  closing tag
• A nested tag pair cannot overlap another tag
• Attribute values must appear within quotes
• Every document must have a root element

9
XML Editor

• XML documents are raw text documents
• Any simple text editor can be used as an XML
  editor
• For eg., Windows users can use windows notepad or
  Wordpad
• Microsoft XML editor Microsoft XML notepad
• Java based XML editor

10
XML Document

• ltexampledocgt - the root element of the document.
• lteqgt - a question and its associated answers.
• question a question.
• a the first possible answer to a question.
• b the second possible answer to a question
• c the third possible answer to a question.

11
XML Document (contd)

• lt?xml version 1.0?gt
• ltexampledocgt
• lteq answer agt
• ltQuestiongt
• In 1994, a man had an accident
  while robbing a pizza restaurant in Akron, Ohio,
  that resulted in his arrest. What happened to
  him?
• lt/Questiongt

12
XML Document (contd)

• ltAgt he slipped on a patch of grease on the
  floor and knocked himself out. lt/Agt
• ltBgthe backed into a police car while
  attempting to drive off. lt/Bgt
• ltCgthe choked on a breadstick that he had
  grabbed as he was running out. lt/Cgt
• lt/ttgt
• lt/exampledocgt

13
Viewing XML Document

• Style sheet is the best way to view an XML
  document.
• Style sheet is a series of formatting
  descriptions that determines how elements are
  displayed on a web page.
• In simple english, a style sheet controls how a
  web page content looks like in a web browser.

14
A CSS for Example doc XML Document

• CSS for eq tag
• eq
• Display block
• Width 750px
• Padding 10px
• Margin-bottom 10px
• Border 4px double black
• Background color silver

15
Style Sheets (contd)

• In the absence of a style sheet, internet
  explorer or any browser just displays the XML
  code
• To attach the style sheet to the document, add
  the following line of code just after the XML
  declaration for the document
• lt?xml-stylesheet type text/css
  hrefexampledoc.css?gt

16
Is XML a Database?

• XML and its surrounding technologies constitute a
  "database" in the looser sense of the term i.e.
  database management system (DBMS).
• XML provides many of the things found in
  databases storage (XML documents), schemas
  (DTDs, XML schema languages)
• Query languages (XQuery, XPath, XQL, XML-QL,
  QUILT, etc.), programming interfaces (SAX, DOM,
  JDOM) etc.

17
Is XML a Database? Contd..

• But lacks many of the things found in real
  databases efficient storage, indexes,
  security,transactions and data integrity,
  multi-user access, triggers, queries across
  multiple documents
• Use XML documents as database in environments
  with small amounts of data, few users, and modest
  performance requirements.
• Fails in an environment, with many users, strict
  data integrity requirements, and the need for
  good performance.

18
XML And Databases

• XMLs proliferation raises questions how is data
  transferred by XML documents to be read, stored
  and queried.
• In other words how do DBMSs handle XML
  documents???
• Two ways to look at XML Documents Data-Centric
  and Document Centric documents.

19
Data Centric Documents

• Data-Centric documents use XML as a data
  transport
• Such documents usually are found in
  business-to-business applications
• Examples Buyer-supplier trading automation,
  Sales orders, Flight Schedules, Scientific data
• Data-centric documents have a regular structure
• Data originates both in the database (in which
  case we want to expose it as XML) and outside the
  database (in which case we want to store it in a
  database)

20
Example - Data Centric Document
ltEmployeesgt ltEmployee JobCode"A1"gt ltDept
No"1"/gt ltEmpNogt1234lt/EmpNogt
ltFirstNamegtJohnlt/FirstNamegt
ltLastNamegtDoelt/LastNamegt ltHireDategt1998-02-11lt
/HireDategt lt/Employeegt ltEmployee
JobCode"B3"gt ltDept No"2"/gt
ltEmpNogt5678lt/EmpNogt ltFirstNamegtJoylt/FirstNamegt
ltLastNamegtBlacklt/LastNamegt
ltHireDategt1998-03-09lt/HireDategt
lt/Employeegt lt/Employeesgt
21
Data Centric Documents

• To manage Data-Centric documents, there need to
  be data extraction as well as data formatting
  services
• Data Extraction Receive XML documents from a
  network, and extract structured data from them,
  to be stored in a DBMS
• To support data extraction, a mapping must be
  defined between XML documents and the DBMS data
  model
• Data extracted stored in a table, follows a
  predefined schema. (that is why called a
  structured representation)
• The original XML documents structure is not
  maintained in this case

22
Example Data Extraction
ltclientsgt ltrowgt ltnumbergt 7369 lt/numbergt ltfirstname
gt Paul lt/firstnamegt ltlastnamegt Smith
lt/lastnamegt lt/rowgt ltnumbergt 7000
lt/numbergt ltfirstnamegt Steve lt/firstnamegt ltlastname
gt Adam lt/ lastnamegt lt/rowgt lt/clientsgt

• Number First Name Last Name
• Steve Adam
• 7369 Paul Smith

23
Data Centric Documents

• Data Formatting XML encoding software, takes
  result of a query expressed in a DBMS Query
  language, and encode the resulting data in an XML
  document to be transferred over the network.
• To support data formatting, implement a sort of a
  reverse formatting with respect to data
  extraction
• After a set of tuples is selected from the
  database with a database query, data formatting
  services transform it into an XML document

24
Data Formatting - Data centric document
Select FirstName, LastName From Clients Where
number 7369
Table Clients
Xml document ltclientsgt ltrowgt ltfirstn
amegt Paul lt/firstnamegt ltlastnamegt Smith
lt/lastnamegt lt/rowgt lt/clientsgt
25
Document Centric Documents

• In this view, XML documents are
  application-relevant objects, i.e. new data
  objects to be stored and managed by a DBMS
• The meaning of the XML document depends on the
  document as a whole.
• Structure is more irregular, and data are
  heterogeneous
• Examples books, email, advertisements
• Unlike data-centric documents, they usually do
  not originate in the database

26
Document Centric Documents

• Document centric documents are application-relevan
  t objects
• The meaning of the XML document depends on the
  document as a whole.
• Structure is more irregular, and data are
  heterogeneous
• Unlike data-centric documents, they usually do
  not originate in the database

27
Example - Document Centric Documents
ltProductgt ltIntrogt The ltProduct NamegtTurkey
Wrench lt/Product Namegt from ltDevelopergtFull
Fabrication Labs, Inc.lt/Developergt is
ltSummarygtlike a monkey wrench, but not as
big.lt/Summarygt lt/Introgt ltDescriptiongt ltParagtThe
turkey wrench, which comes in ltigtboth right- and
left-handed versions (skyhook optional)lt/igt,is
made of the ltbgt finest stainless steellt/bgt. The
Ready-grip rubberized handle quickly adapts to
your hands your hands, even in the greasiest
situations. Adjustment is possible through a
variety of custom dials.lt/Paragt ltParagtYou
canlt/Paragtltlistgt ltItemgtltLink URL"Order.html"gtOrd
er your own turkey wrenchlt/Linkgtlt/Itemgt lt/listgt lt/
Descriptiongt lt/Productgt
28
Document Centric Documents

• This type of document requires a DBMS enhanced
  with new data types for representing XML data
  types
• New capabilities for querying and managing the
  documents
• Two types of data types devised are
• Unstructured representation
• Hybrid representation

29
Document Centric Documents (Unstructured)

• Unstructured representation
• A single data field inside the DBMS is managed by
  the DBMS
• A single data field outside the DBMS, but linked
  to the DBMS. In this case the operating system
  manages it
• For unstructured XML documents, DBMSs extend
  query languages with XML based selection
  conditions

30
Example - Unstructured
ltclientsgt
ltrowgt 10 ltnumbergt 7369
lt/numbergt ltfirstnamegt Paul lt/firstnamegt ltlastnamegt
Smith lt/lastnamegt lt/rowgt ltrowgt ltnumbergt 7000
lt/numbergt ltfirstnamegt Steve lt/firstnamegt ltlastname
gt Adam lt/lastnamegt lt/rowgt lt/clientsgt
XML Document ltclientsgt ltrowgt ltnumbergt
7369 lt/numbergt ltfirstnamegt Paul
lt/firstnamegt ltlastnamegt Smith lt/lastnamegt lt/rowgt lt
rowgt ltnumbergt 7000 lt/numbergt ltfirstnamegt Steve
lt/firstnamegt ltlastnamegt Adam lt/lastnamegt lt/rowgt lt/
clientsgt
Id
10
31
Document Centric Documents --Hybrid

• Hybrid Representation
• Combination of Structured and unstructured type.
• Useful while mixing types, such as structural
  information about a book, but unstructured
  information consisting of the contents or
  chapters of the book.

32
Example -- Hybrid
33
Commercial Support In Databases

• Oracle 8i
• Has extended architecture with tools to manage
  XML documents
• Supports structured, unstructured and hybrid
  representation of XML documents
• XML-SQL utility supports data extraction and data
  formatting for data-centric documents
• Document-centric data stored using CLOB
  (character large object)

34
Commercial Support In Databases

• IBM DB2
• The XML Extender provides features to store and
  manage XML documents
• Handles structured, unstructured as well as
  hybrid types
• Data centric documents stored in a set of
  relational tables containing data extracted from
  XML documents
• The Extender supports storage and access methods
  to compose an XML document from existing data or
  decompose data from an XML document

35
Commercial Support In Databases

• Document-centric documents stored as either
  XMLClob or XMLVarChar or XML File
• Microsoft SQL Server
• Data-centric The OpenXML function extracts data
  from XML document and stores it in a relational
  database
• Extending the Select-From-Where statement with
  the FOR XML clause provides XML formatting of a
  query language
• Permits construction of XDR Schemas Schemas that
  generate views of the database in XML format,
  which can be queried with XPath.

36
Data-centric and Document-centric

• In practice, the distinction between data-centric
  and document-centric documents is not always
  clear.
• For example, a data-centric document, such as an
  invoice, might contain irregularly structured
  data, such as a part description.
• An otherwise document-centric document, such as a
  user's manual, might contain regularly
  structured data (often metadata), such as an
  author's name and a revision date.

37
Document Schema,Database Schema

• A schema is a set of rules that defines the
  structure of any document or database
• Database schema describes over all structure of
  the database.
• Document schema describes exact elements and
  attributes available with in a given markup
  language along with association between
  attributes and elements and relationship between
  elements
• The schema will allow XML documents to be
  validated for accuracy

38
Document schemas

• There are two different approaches for creating
  schemas in XML documents
• Document Type Definition(DTD)
• XML Schema Definition(XSD)
• A DTD describes vital information about the
  structure of XML document i.e, it lists element
  types,attributes and their relationships to each
  other
• It sets out what names are to be used for the
  different types of element, where they may occur,
  and how they all fit together

39
Limitations of DTD

• Non XML syntax
• No data-type facility
• Employs a closed-data model which does not allow
  much flexibility to extend markup languages

40
XML Schema

• XSDs are not only significant in defining XML
  structures but also in providing data type
  capabilities to XML
• Coded in XML tags
• Supports Integrity constraints such as Primary
  and foreign keys etc.
• Represents an open-ended data model allowing to
  extend custom markup languages and establishing
  complex relationships between elements

41
Mapping Document Schemas to Database
Schema

• Two mappings used commonly Table-based mapping
  and Object-relational mapping
• The data transfer software is built on top of
  this mapping.
• Use an XML query language (such as XPath, XQuery,
  or a proprietary language)
• OR
• Simply transfer data according to the mapping
  (the XML equivalent of SELECT FROM Table).

42
Table Based mapping

• Used by many of the middleware products that
  transfer data between an XML document and a
  relational database
• It models XML documents as a single table or set
  of tables. That is, the structure of an XML
  document must be as follows
• ltdatabasegt
• lttablegt
• ltrowgt
• ltcolumn1gt...lt/column1gt
• ltcolumn2gt...lt/column2gt
• ...
• lt/rowgt
• ltrowgt
• ...
• lt/rowgt
• ...
• lt/tablegt
• lttablegt
• ...
• lt/databasegt

43
Table based mapping

• Advantages
• Its simplicity because it matches
  structure of tables and result sets in
  relational databases
• Mainly useful for transferring data
  between databases
• Disadvantages
• Applies to only limited set of XML documents
• It doesn't exploit ability of XML to
  represent hierarchies of data
• It doesnt preserve physical structure
  i.e., DTD

44
Object-relational mapping

• The object-relational mapping is used by all
  XML-enabled relational databases and some
  middleware products.
• It models the data in the XML document as a tree
  of objects that are specific to the data in the
  document.
• Objectrelational mapping is done in two steps
• An Document Schema( DTD) is mapped to object
  schema
• The object schema is mapped to database
  schema

45
Object-relational mapping Contd..

• In this model, element types with attributes are
  generally modeled as classes.
• The model is then mapped to relational databases
  using traditional object-relational mapping
  techniques
• i.e. Classes are mapped to tables, scalar
  properties are mapped to columns, and object
  valued properties are mapped to primary key /
  foreign key

46
Object-relational mapping - contd
For example , consider the following XML document
ltSalesOrdergt ltNumbergt1234lt/Numbergt
ltCustomergtABC Industrieslt/Customergt
ltDategt29.10.00lt/Dategt ltItem Number"1"gt
ltPartgt123lt/Partgt ltQuantitygt12lt/Quant
itygt ltPricegt10.95lt/Pricegt lt/Itemgt
ltItem Number"2"gt ltPartgt456lt/Partgt
ltQuantitygt600lt/Quantitygt
ltPricegt3.99lt/Pricegt lt/Itemgt lt/SalesOrdergt
47
Object-relational mapping Contd..
Which maps to the following objects
Object SalesOrder number 1234 Customer
ABC Industries orderdate 12.15.98 Items
ptrs to Item Objects
Object Item Number 2 Part 456 Quantity
600 Price 3.99
Object Item Number 1 Part 123 Quantity
12 Price 10.95
48
Object-relational mapping Contd..
and then to rows in the following tables
SaleOrders ---------- Number Customer
Date ------ --------------------
-------- 1234 ABC Industries
29.10.00 ... ... ...
... ... ...
Items ----- SONumber Item Part
Quantity Price -------- ----
---- -------- ----- 1234 1
123 12 10.95 1234
2 456 600 3.99 ... ...
... ... ...
49
Query Languages

• Use of XSLT or Integrate limited number of
  transformations into mappings
• Long TermImplementation of query languages that
  return XML
• Almost all of XML query languages (including
  XQuery 1.0) are read-only, so different means
  needed to insert, update, and delete data
• In the long term, XQuery will add these
  capabilities

50
Template-Based Query Languages

• Most of these languages rely on SELECT statements
  embedded in templates
• lt?xml version"1.0"?gt
• ltFlightInfogt
• ltIntroductiongtThe following flights have
  available
• seatslt/Introductiongt
• ltSelectStmtgtSELECT Airline, FltNumber, Depart,
  Arrive FROM
• Flightslt/SelectStmtgt
• ltFlightgt
• ltAirlinegtAirlinelt/Airlinegt
• ltFltNumbergtFltNumberlt/FltNumbergt

51
Template-based Query languages - contd

• The result of processing such a template might
  be
• lt?xml version"1.0"?gt
• ltFlightInfogt
• ltIntroductiongtThe following flights have
  available
• seatslt/Introductiongt
• ltFlightsgt
• ltFlightgt
• ltAirlinegtACMElt/Airlinegt
• ltFltNumbergt123lt/FltNumbergt
• ltDepartgtDec 12, 1998 1343lt/Departgt
• ltArrivegtDec 13, 1998 0121lt/Arrivegt
• lt/Flightgt ...

52
SQL Based Query Languages

• SQL-based query languages use modified SELECT
  statements, the results of which are transformed
  to XML
• The simplest of these uses nested SELECT
  statements, which are transformed directly to
  nested XML according to the object-relational
  mapping

53
XML Query Languages

• Template-based query languages and SQL-based
  query languages can only be used with relational
  databases
• XML query languages can be used over any XML
  document
• To use with relational databases, the data in the
  database must be modeled as XML, thereby allowing
  queries over virtual XML documents
• There are different types of XML Query languages
  such as XQuery ,XPath etc .,

54
XQuery -- An Introduction

• XQuery is a functional language in which a
  query is represented as expression
• An XQuery expression leverages the capabilities
  of XML by allowing both specification of what is
  being selected and designation of output format.
• There are several types of expressions used in
  Xquery such as path expressions, element
  constructors, FLWR expressions, conditional
  expressions etc.,,

55
XQuery

• Either a table-based mapping or an
  object-relational mapping can be used
• If a table-based mapping is used, each table is
  treated as a separate document and joins between
  tables (documents) are specified in the query
  itself, as in SQL
• If an object-relational mapping is used,
  hierarchies of tables are treated as a single
  document and joins are specified in the mapping

56
Xpath - An Introduction

• XPath is a set of syntax rules for defining parts
  of an XML document
• XPath uses path expressions to identify nodes in
  an XML document
• These path expressions look very much like the
  expressions you see when you work with a computer
  file system

57
XPath

• An object-relational mapping is used to do
  queries across more than one table (Xpath does
  not support joins across documents)
• If the table-based mapping used, it is possible
  to query only one table at a time

58
Native XML Databases (NXD)

• A native XML database defines a logical model
  for an XML document-as opposed to data in that
  document-and stores and retrieves documents
  according to that model.
• The model must include elements, attributes,
  PCDATA and document order.
• Eg Xpath data model, the XML Infoset, and the
  most models implied by the DOM and the events in
  SAX.

59
NXDs (contd)

• It has an XML document as its fundamental unit
  of logical storage.
• Any particular underlying physical storage model
  is not required.
• An NXD does not really store the XML in true
  native form (i.e., text).

60
NXDs in Brief

• It is specialized for storing XML data and stores
  all components of XML model intact.
• An NXD may not actually be a standalone database.
• It does not represent a new low-level database
  model, and is not intended to replace existing
  databases.
• Is simply a tool intended to assist the developer
  by providing robust storage and manipulation of
  XML documents.

61
NXD Features

• XML Storage
• NXDs store XML documents as a unit and will
  create a model that is closely aligned with XML
  or one of XMLs technologies like the Infoset or
  DOM.
• Includes arbitrary levels of nesting and
  complexity.
• This model is automatically mapped by the NXD
  into the underlying storage mechanism.

62
NXD Features (contd)

• Collections
• NXDs manage collections of documents, allowing
  you to query and manipulate those documents as a
  set.
• Any XML document can be stored in the collection,
  regardless of the schema Schema-Independent
  functionality.
• In the future, it is likely that W3C XML Schema
  will emerge as the schema language of choice for
  NXDs.

63
NXD Features (contd)

• Queries
• XPath is the current NXD query language of
  choice.
• In order to function as a database query
  language, XPath is extended slightly to allow
  queries across collections of documents.
• XPath has several shortcomings which include lack
  of grouping, sorting, cross documented joints and
  support for data types.
• These issues can be resolved by XSLT and XQuery.

64
NXDs (contd)

• Native XML databases are the databases designed
  especially to store XML documents.
• Like other databases, they support features like
  transactions, security, multi user access, query
  languages etc.,
• They are mainly useful for storing
  document-centric documents.
• NXDs support XML query languages that execute
  complex queries which are not possible in sql.
• Eg.,In NXDs, data can be retrieved based on the
  structural information, which is not possible in
  SQL.

65
NXDs (contd)

• NXD offers XML-specific capabilities such as, XML
  query languages and will be faster at retrieving
  whole document.
• In NXDs we can store semi-structured data i.e.,
  documents that do not have DTDs, to increase
  retrieval speed.
• NXDs can store and understand any XML document
  without prior configuration.
• Eg., Web search engines where no single or set
  of DTDs apply to all documents.

66
Application Areas of NXD

• Any application area that uses XML can use NXD.
• In general, NXDs excel at storing
  document-oriented data (eg., XHTML or DocBlock).
• If the data is represented as XML and is kind of
  fuzzy, an NXD will probably be a good solution.
• An NXD might not be the best tool to for
  something like an accounting system where the
  data is very well-defined and rigid.

67
Application Areas (contd)

• Corporate Information Portals
• Catalog Data
• Manufacturing Parts Database
• Medical Information Storage
• Document Management Systems
• B2B Transaction Logs
• Personalization Databases.

68
XML Programming Interfaces

• Programming interfaces give developers a
  consistent interface for working with XML
  documents. There are four of the most popular and
  useful ones
• Document Object Model (DOM)
• Simple API for XML (SAX)
• JDOM
• Java API for XML Parsing (JAXP).

69
XML Parsers

• XML Parsers are programs which are able to read
  XML syntax and get information required out of
  it.
• There are two kinds of XML Parsers
• Non-valid. For e.g. LARK, XP and HEX etc
• Valid For e.g. IBM's XML Parser for Java which
  include DOM and SAX, Oracle XML parser,
  XMLbooster and DXP etc

70
Relationship Between XML Documents, Parsers and
Applications
XML parser
XML DTD (optional)
Application
Document
71
Document object Model

• DOM was created by the W3C, and is an Official
  Recommendation of the consortium.
• It is defined as a set of interfaces to the
  parsed version of an XML document.
• DOM provides a rich set of functions that you can
  use to interpret and manipulate an XML document
•  

72
Parse Get Info
XML Document
DOM
XML Parser
Application
73
DOM issues

• It requires a significant amount of memory.
• The DOM creates objects that represent everything
  in the original document, including elements,
  text, attributes, and white space.
• A DOM parser causes significant delays for large
  documents.

74
The Simple API for XML(SAX)

• To get around the DOM issues, the XML-DEV
  participants (led by David Megginson) created the
  SAX interface.
• A SAX parser is event based.
• A SAX parser doesn't create any objects at all,
  it simply delivers events to your application.
• A SAX parser starts delivering events as soon as
  the parse begins and the application starts
  generating results right away.

75
Parse Information
XML Document
XML Parser
Application
Event handlers
76
SAX issues

• SAX events are stateless
• SAX events are not permanent.
• SAX is not controlled by a centrally managed
  organization

77
JDOM

• Frustrated by the difficulty in doing certain
  tasks with the DOM and SAX models, Jason Hunter
  and Brett McLaughlin created the JDOM package
• JDOM is a Java based-technology, open source
  project that attempts to follow the 80/20 rule
• JDOM works with SAX and DOM parsers
• The main feature of JDOM is that it greatly
  reduces the amount of code

78
The Java API for XML Parsing(JAXP)

• There are still several things that DOM, SAX, and
  JDOM dont address. So, Sun has released JAXP,
  the Java API for XML Parsing.
• JAXP provides common interfaces for processing
  XML documents using DOM, SAX, and XSLT.

79
Which interface is right for you?

• Will your application be written in Java?
• How will your application be deployed?
• Once you parse the XML document, will you need to
  access that data many times?
• Do you need just a few things from the XML
  source?
• Are you working on a machine with very little
  memory?

80
Applications Of XML

• There are several applications of XML which are
• Wireless Markup Language (WML) It is an XML
  application which is designed specifically to
  support wireless communication networks.
• MathML It is an XML application which supports
  mathematical and scientific markups for the use
  on the web.
• Scalable Vector Graphics (SVG) It is an
  application of XML which is used for describing
  two-dimensional graphics in XML.

81
Applications Of XML (contd.)

• Resource Description Framework (RDF) A framework
  for metadata to assure interoperability between
  applications.
• Synchronized Multimedia Integration Language
  (SMIL) SMIL enables to integrates independent
  multimedia objects into synchronized multi media
  presentation.
• Web Services A tool to access the Web browser,
  such as SOAP, UDDI, WSDL, all these are XML based
  technologies.
• Other applications include VoiceML, VectorML and
  MusicML etc.

82
Conclusion

• Even though current DBMSs support XML, several
  problems remain to be investigated.
• Development of clustering algorithms for
  persistent XML documents
• Extension of support for XML query languages in
  commercial databases
• Development of access control models to provide
  more secure content based access to XML
  documents
• Development of ad hoc indexing structures for
  more efficient document access
• Data centric Architectures need flexible
  extraction and formatting mechanisms
• Architectural support for document-centric
  document management