Understanding XML and Its Impact on the Enterprise

1
Understanding XML and Its Impact on the Enterprise
2
Outline

• Why XML is the cornerstone of the Semantic Web
• Why XML has achieved widespread adoption and
  continues to expand to new areas of information
  processing
• How XML works and the mechanics of related
  standards like namespaces and XML schema
• The impact of XML on the enterprise
• Why XML itself is not enough

3
Introduction

• Currently, primary use of XML is for data
  exchange between internal and external
  organizations (interoperability)
• XML may become the primary syntax for all
  enterprise data
• As XQuery and XML Schema achieve greater maturity
  and adoption

4
Why Is XML a Success?

• XML creates application-independent documents and
  data
• It has a standard syntax for meta data
• It has a standard structure for both document and
  data
• XML is not a new technology (not a 1.0 release)

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XML creates application-independent documents and
data

• Plaintext in human-readable form
• Binary formats lock into applications for the
  life of your data
• Encoding XML as text allows any program to open
  and read the file
• By using an open, standard syntax and verbose
  descriptions of the meaning of data, XML is
  readable and understandable by everyone not
  just the application and person that produced
• Critical underpinning of the Semantic Web,
  because you cannot predict the variety of
  software agents and systems that will need to
  consume data on Web
• XML can be searched as easily as Web pages

6
XML has a standard syntax for meta data

• Meta data data about data (meaning of data
  values)
• Data is the raw context-specific value and the
  meta data denotes the meaning or purpose of those
  values
• XML standardizes a simple, text-based method for
  encoding meta data
• XML provides a simple yet robust mechanism for
  encoding semantic information, or the meaning of
  data

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Comparing Data to Meta Data
ltNamegt Joe Smith lt/NamegtltAddressgt222 Happy
Lanelt/AddressgtltCitygtSierra Vistalt/CitygtltStategtAZ
lt/StategtltZipgt85645lt/Zipgt
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XML has a standard structure for both documents
and data

• XML standardize a structure suitable to express
  semantic information for both documents and data
  fields
• The structure XML uses is a hierarchy or tree
  structure
• Allow the user to decompose a concept into its
  component parts in a recursive manner

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person.xml

• ltpersongt
• ltnamegt
• ltfirst_namegtAlanlt/first_namegt
• ltlast_namegtTuringlt/last_namegt
• lt/namegt
• ltprofessiongtComputer Scientistlt/professiongt
• ltprofessiongtMathematicianlt/professiongt
• ltprofessiongtCryptographerlt/professiongt
• lt/persongt

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A Tree Diagram for person.xml
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XML is not a new technology

• SGML (Standardized Generalized Markup Language)
• Invented in 1969
• XML is an abbreviated version of SGML
• Omit more complex and less-used parts of SGML
• Easier to define new document types
• Easier to write program to handle XML documents
• More suited to delivery and interoperability over
  WWW
• XML is more SGML-- rather than HTML
• XML is SGML for the Web

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What is XML?

• XML eXtensible Markup Language
• XML is NOT a set of tags that you can apply to
  documents
• XML is a a set of syntax rules for the creating
  semantically rich markup languages in a
  particular domain (eXtensible)
• XML does not define the tag (element) names YOU
  DO
• XML is NOT a programming language like C
• XML is NOT a network transport protocol like
  HTTP, FTP
• XML is NOT a database
• A database can contain XML data, but the database
  itself is not an XML document
• You can store XML data into a database or
  retrieve XML data from a database, but you need
  to run software written in a real programming
  language such as C and Java

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Why Should Documents Be Well-Formed and Valid?

• A well-formed XML document complies with all the
  W3C syntax rules of XML like naming, nesting, and
  attribute quoting
• Guarantee that an XML processor can parse the
  document (break into identifiable components)
  without error
• A valid XML document references and satisfies a
  schema
• A schema is a separate document whose purpose is
  to define the legal elements, attributes, and
  structure of an XML instance document. Ex. DTD,
  XML Schema
• Think of a schema as defining the legal
  vocabulary, number, and placement of elements and
  attributes in your markup language
• A schema defines a particular type or class of
  documents

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Why Should Documents Be Well-Formed and Valid?

• W3C-compliant XML processors check for
  well-formedness but may not check for validity
• Validation is often a feature that can be turned
  on or off in an XML parser
• Validation is time-consuming and not always
  necessary
• It is generally best to perform validation either
  as part of document creation or immediately after
  creation

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XML NameSpace

• http//www.w3.org/TR/REC-xml-names

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Motivation

• XML is extensible
• But, extensibility does not come free
• Extensibility must be managed to avoid conflicts
• Namespaces is a solution to help manage XML
  extensibility
• Example two people extend the same document in
  incompatible ways
• bookmark.xml
• star_rating.xml
• pa_rating.xml
• star_pa_rating.xml

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Motivation (Cont.)

• Problems in star_pa_rating.xml
• Software designed to operate with PA rating would
  be lost
• How to do with 4 stars rating?
• Ignore?
• No way to differentiate PA rating with Star
  rating
• Brute-force solution Use different names for the
  two rating
• qa_pa_rating.xml

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Motivation (Cont.)

• Documents that contain multiple markup (meta
  data) vocabularies pose problems of recognition
  and collision.
• Software modules need to be able to recognize the
  tags and attributes which they are designed to
  process, even in the face of "collisions"
  occurring when markup intended for some other
  software package uses the same element type or
  attribute name.
• These considerations require that document
  constructs should have universal names, whose
  scope extends beyond their containing document.
  This specification describes a mechanism, XML
  namespaces, which accomplishes this.

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Declaration

• ltelement xmlnsprefixnamespace_urigt
• lttitle xmlnsdchttp//purl.org/dcgt
• Default namespace
• ltelement xmlnsnamespace_urigt
• lttitle xmlnshttp//purl.org/dcgt
• Example namespace_bookmark.xml
• ltqaratinggt5 stars lt/qaratinggt
• A prefix is added before each element name
• A colon separates the name and the prefix
• The prefixes of default namespace can be omitted.

URI is unique!!!
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Definition

• An XML namespace is a collection of names,
  identified by a URI reference, which are used in
  XML documents as element types and attribute
  names.
• URI references which identify namespaces are
  considered identical when they are exactly the
  same character-for-character.
• Note that URI references which are not identical
  in this sense may in fact be functionally
  equivalent.
• Examples include URI references which differ only
  in case, or which are in external entities which
  have different effective base URIs.

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Names from XML NameSpaces

• Names from XML namespaces may appear as qualified
  names, which contain a single colon, separating
  the name into a namespace prefix and a local
  part.
• The prefix, which is mapped to a URI reference,
  selects a namespace.
• The combination of the universally managed URI
  namespace and the document's own namespace
  produces identifiers that are universally unique.
• Mechanisms are provided for prefix scoping and
  defaulting.
• An attribute-based syntax described below is used
  to declare the association of the namespace
  prefix with a URI reference
• Software which supports this namespace proposal
  must recognize and act on these declarations and
  prefixes.

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Namespaces and Schemas

• Namespaces are not fully compatible with DTDs
• The current markup definition languages, like XML
  Schema, fully support namespaces
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt

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XML Schema

• http//www.w3c.org/XML/Schema

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XML Schema

• A definition language that enables you to
  constrain conforming XML documents to a specific
  vocabulary and a specific hierarchical structure
• Element types, attribute types, complex types
• Two types of documents a schema document and
  multiple instance documents that conform to the
  schema
• A schema definition is a blueprint (template) of
  a type and each instance is an incarnation of
  that template
• Two roles that a schema can play
• Template for a form generator to generate
  instances of a document type
• Validator to ensure the accuracy of documents

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Schema and Instances
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XML Schema (Cont.)

• Both the schema document and the instance
  document use XML syntax (tags, elements, and
  attributes)
• Each instance document must declare which schema
  it adhere to
• Use a special attribute attached to the root
  element called"xsinoNamespaceSchemaLocation"
  or"xsischemaLocation"
• Depend on whether your vocabulary is defined in
  the context of a namespace
• XML Schemas allow validation of instances to
  ensure the accuracy of field values and document
  structure at the time of creation
• Field types, legal element and attribute names,
  correct number of children, and required
  attributes

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What do Schemas Look Like?

• An XML Schema uses XML syntax to declare a set of
  simple and complex type declarations
• A type is named template that can hold one or
  more values
• Simple types hold one value
• Complex types are composed of multiple simple
  types
• A type has two key characteristics a name and a
  legal set of values
• Simple type an element declaration that includes
  its name and value constraints
• ltxsdelement name"author" type"xsdstring" /gt
• ltauthorgt Mike Daconta lt/authorgt

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Common XML Schema Primitive Data Types
You can define custom data types
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Define Custom Data Types
ltxsdsimpleType name"skuType"gt
ltxsdrestriction base"xsdstring"gt
ltxsdpattern value"\d 3 -A-Z 2 "/gt
lt/xsdrestrictiongt lt/xsdsimpleTypegt
ltxsdsimpleType name"stateType"gt
ltxsdrestriction base"xsdstring"gt
ltxsdenumeration value"AK"/gt
ltxsdenumeration value"AL"/gt
ltxsdenumeration value"AR"/gt ...
lt/xsdrestrictiongt lt/xsdsimpleTypegt

ltxsdsimpleType name"poIdType"gt
ltxsdrestriction base"xsdinteger"gt
ltxsdminExclusive value"10000"/gt
ltxsdmaxExclusive value"100000"/gt
lt/xsdrestrictiongt lt/xsdsimpleTypegt
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What do Schemas Look Like? (Cont.)

• Complex type an element that either contains
  other elements or has attached attributes
• ltxsdelement name"book" ltxsdcomplexTypegt
  ltxsdattribute name"title" type"xsdstring" /gt
  ltxsdattribute name"pages" type"xsdint" /gt
  lt/xsdcomplexTypegtlt/xsdelementgt
• ltbook title"More Java Pitfalls" page"453" /gt

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What do Schemas Look Like? (Cont.)

• Another example of Complex type
• ltxsdelement name"product" ltxsdcomplexTypegt
  ltxsdsequencegt ltxsdelement
  name"description" type"xsdstring"
  minOccurs"0" maxOccurs"1" /gt ltxsdelement
  name"category" type"xsdstring"
  minOccurs"1" maxOccurs"unbounded" /gt lt/xsd
  sequencegt ltxsdattribute name"id"
  type"xsdID" /gt ltxsdattribute name"title"
  type"xsdstring" /gt ltxsdattribute
  name"price" type"xsddecimal" /gt
  lt/xsdcomplexTypegtlt/xsdelementgt

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What do Schemas Look Like? (Cont.)

• ltproduct id"P01" title"Wonder Teddy"
  price"49.99"gt ltdescriptiongt The best selling
  teddy bear of the year. lt/descriptiongt
  ltcategorygt toys lt/categorygt ltcategorygt stuffed
  animals lt/categorygtlt/productgt
• ltproduct id"P02" title"RC Racer"
  price"89.99"gt ltcategorygt toys lt/categorygt
  ltcategorygt electronic lt/categorygt ltcategorygt
  radio-controlled lt/categorygt
• lt/productgt

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What do Schemas Look Like? (Cont.)

• Let's Look at a more complex Schema po.xsd

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Purchase Order Schema
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Reusability

• Basic reusability mechanisms address the problems
  of using existing assets in multiple places.
• Element references
• Content model groups
• Attribute groups
• Schema includes
• Schema imports
• Advanced reusability mechanisms address the
  problems of modifying existing assets to serve
  needs that are perhaps different from what they
  were originally designed for
• Exploit object-oriented idea
• Extension and Restrictions

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Is Validation Worth the Trouble?

• Validation, and the tool support for it, is still
  evolving
• Until the schema languages mature, validation
  will be a frustrating process that requires
  testing with multiple tools
• Validation is a critical component of your data
  management process, because
• XML is intended to be shared and processed by a
  large number and variety of applications
• A source document may be broken up into XML
  fragments and parts reused ? the cost of errors
  in XML must be multiplied across all the programs
  and partners that rely on that data
• The chief difficulties with validation data
  types, namespace support, and type inheritance

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Document Object Model (DOM)
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What is the DOM?

• The DOM is a platform- and language-neutral data
  model and application programming interface (API)
  that will allow programs to dynamically
  manipulate the content, structure and style of
  XML and HTML documents
• DOM is a object-oriented data model, using
  objects, to represent an XML or HTML document
• Status of DOM
• DOM Level1 W3C recommendation, 1 Oct. 1998.
• DOM Level2 W3C recommendation, 13 Nov. 2000.
• DOM Level3 W3C candidate recommendation, 7 Nov.
  2003

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The DOM structure model

• DOM is as a set of classes that allow you to
  create a tree of objects in memory that represent
  a manipulable version of an XML or HTML document
• DOM presents documents as a hierarchy of Node
  objects that also implement other, more
  specialized interfaces
• Everything in an XML document is a node object
• Some types of nodes may have child nodes of
  various types, and others are leaf nodes that
  cannot have anything below them in the document
  structure.

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Class and Objects
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A DOM as A Tree of Nodes
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A DOM as A Tree of Subclasses
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The DOM Interface

• The DOM has many interfaces to handle various
  node objects.
• Every interface has its Attributes and
  Methods.
• Compare with Object Oriented Programming (OOP).

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The DOM Interface Hierarchy
Fundamental Interface
DOMImplementation
NamedNodeMap
DOMException
NodeList
Node
Document
CharacterData
Comment
Attr
Text
Element
Extended Interface
DocumentType
CDATASection
Notation
Entity
EntityReference
ProcessingInstruction
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The Simple Hierarchy of An XML Document
Document
NodeList
Element
Node
NodeList
Node
Node
Comment
Node
Node
Text
Node
Node
Node
Attr


Node
Node
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The Hierarchy of An XML Document

• lt?xml version"1.0" encoding"big5"?gt
• ltMemberDatagt
• ltUserNamegtclavenlt/UserNamegt
• ltRealNamegt???lt/RealNamegt
• ltTELDatagt
• ltTELgt03-5712121lt/TELgt
• ltExtgt12345lt/Extgt
• lt/TELDatagt
• ltAddr typeOfficegt?????????lt/Addrgt
• lt/MemberDatagt

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The Simple Hierarchy of an XML Document
Document
NodeList
Element (root MemberData)
Node
NodeList
Node
Element (UserName)
Node
Element (RealName)
Node
Element (TELData)
Node
Element (TEL)

NodeList
Node
Element (Ext)
Node
Element (Addr)
NodeList
NodeList
Attr (type)
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The Relation Graph
Web Client side program (e.g. JavaScript) Web
Server side program (e.g. ASP) Console program
(e.g. C, Java)
DOM
Output
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An Example Most Frequently Used Interface, Node

• Attributes
• childNodes Return the child nodes in a NodeList
• nodeName Return the name of the node
• nodeValue Return the value of the node
• firstChild, lastChild, previousSibling,
  nextSibling, etc.
• Methods
• insertBefore, replaceChild, removeChild,
  appendChild, etc.

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DOM in Programming Languages

• Actually, most programming languages support DOM.
• Java, C, C, VB.Net, etc.
• And almost these programming languages supply
  more convenient attributes and methods than
  standard W3C DOM.

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Impact of XML on Enterprise IT

• Data exchange and interoperability
• By agreeing on a standard schema, organization
  can produce these text documents that can be
  validated, transmitted, and parsed by any
  application regardless of hardware or operating
  system
• The next Electronic Data Interchange (EDI)
• Easy data exchange is the enabling technology
  behind ebusiness and Enterprise Application
  Integration
• Ebusiness
• B2B revolves around the exchange of business
  messages to conduct business transactions
• Web services and Web service registries will
  increase the B2B trend by making it even easier
  to deploy such solutions

53
Impact of XML on Enterprise IT (Cont.)

• Enterprise Application Integration (EAI)
• EAI is the assembling of legacy applications,
  databases, and systems to work together to
  support integrated Web views, e-commerce, and ERP
• Open Applications Group (http//www.openapplicatio
  ns.org) defines standard for application
  integration
• EAI has proven to be the killer app for Web
  services
• Enterprise IT architectures
• Bridge between J2EE and .NET
• XSLT, XML config. files, XMLRDBMS, Native XML
  databases

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Impact of XML on Enterprise IT (Cont.)

• Content Management Systems (CMS)
• CMS is a Web-based system to manage the
  production and distribution of content to
  intranet and Internet sites
• XML separates raw content from its presentation ?
  REUSE
• Content can be transformed on the fly via XSLT to
  browsers or wireless clients
• The ability to tailor content to user groups on
  the fly will continue to drive the use of XML for
  CMS systems
• Knowledge management and e-learning
• XML is driving the future of knowledge management
  in terms of knowledge representation (RDF),
  taxonomies, and ontologies
• XML is fostering e-learning with standard formats
  like the Instructional Management System (IMS)
  XML standards (http//www.imsproject.org)

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Impact of XML on Enterprise IT (Cont.)

• Portals and data integration
• A portal is a customizable, multipaned view
  tailored to support a specific community of users
• XML is supported via standard transformation
  portlets that use XSLT to generate specific
  presentations of content, syndication of content,
  and the integration of Web services
• A portlet is a dynamically pluggable application
  that generates content for one pane in a portal
• Syndication is the reuse of content from another
  site
• The most popular format for syndication is an
  XML-based format called the Resource Description
  Framework Site Summary (RSS)

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Impact of XML on Enterprise IT (Cont.)

• Customer relationship management (CRM)
• CRM systems enable an organization's sales and
  marketing staffs to understand, track, inform,
  and service their customers
• CRM involves portals, CMS, data integration, and
  databases
• XML is becoming the glue to tie all these systems
  together to enable the sales force or customers
  (directly) to access information when they want
  and wherever they are
• Databases and data mining
• All the major DB vendors support XML translation
  between relational tables and XML schemas
• XML as a native data type
• Native XML databases for the storage and
  retrieval of XML
• XQuery

57
Impact of XML on Enterprise IT (Cont.)

• Collaboration technologies and peer-to-peer (P2P)
• Collaboration technologies allow individuals to
  interact and participate in joint activities from
  disparate locations over networks
• P2P is a specific decentralized collaboration
  protocol
• XML is being used for collaboration at the
  protocol level, for supporting interoperable
  tools, configuring the collaboration experience,
  and capturing shared content
• Open source JXTA project (http//www.jxta.org)

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Why Meta Data Is Not Enough

• XML meta data is a form of description
• XML describes the purpose or meaning of raw data
  values via a text format to more easily enable
  exchange, interoperability, and application
  independence
• Meta data increases the fidelity and granularity
  of our data
• The current state of meta data is that we attach
  words (or labels) to our data values to describe
  it
• How about sentences, paragraphs
• The motivation for providing richer data
  description is to move data processing from being
  tediously preplanned and mechanistic to dynamic,
  just-in-time, and adaptive

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Why Meta Data Is Not Enough (Cont.)

• Scenario
• The more computers understand, the more
  effectively they can handle complex tasks
• We have not yet invented all the ways a
  semantically aware computing system can drive new
  business and decrease your operation costs
• But to get there, we must push beyond simple meta
  data modeling to knowledge modeling and standard
  know processing
• Simple meta data ? semantic levels ? rule
  languages ? inference engines

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Evolution in Data Fidelity
61
Semantic Levels

• Evolution of data fidelity required for
  semantically aware applications
• Level 1 (Things) XML Schema
• Describe singular concepts or objects
• Capture and process meta data about isolated data
  classes
• Level 2 (Knowledge about Things) RDF and
  taxonomies
• Enable to model statements both about
  relationships between Level 1 objects and about
  how those objects operate
• Level 3 (Worlds) ontologies
• High-fidelity, closed-world models allow you to
  know your customer better, respond faster,
  rapidly set up new business partners, improve
  efficiencies, and reduce operation costs

62
Rules and Logic

• The semantic levels of information provide the
  input for software systems
• The operations that a software system uses to
  manipulate the semantic information will be
  standardized into one or more rule languages
• A rule specifies an action if certain conditions
  are met
• If (x) then y

63
Inference Engines

• Applying rules and logic to our semantic data
  requires standard, embeddable inference engines
• These programs will execute a set of rules on a
  specific instance of data using an ontology

64
Why Meta Data Is Not Enough (Cont.)

• So, meta data is a starting point for semantic
  representation and processing
• The rise of meta data is related to the ability
  to reuse meta data between organizations and
  systems
• XML provides the best universal syntax to do that