An Introduction to Emerging Web Technologies

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An Introduction to Emerging Web Technologies
Dr. Ronald J. Vetter Professor and
Chair Department of Computer Science University
of North Carolina at Wilmington
2
Overview

• Historical Perspective of the Web
• Current Specifications and Practices
• Evolution to the Object Web
• Web Services
• Concluding Remarks

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The Web a radical technology!

• A radical technology is one that will cause a
  fundamental change in the way organizations do
  business.
• How is the Web evolving and what changes can we
  expect to occur in the next 5 years?

4
Challenges Facing the Web

• Prevalence of poor markup practices
• Weak implementations of style sheet support
• New kinds of browsers digital TVs, handheld PCs,
  phones, and cars
• Pressure to subset HTML for simple clients
• Pressure to extend HTML for richer clients

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Challenges Facing the Web, cont.

• Improvements to HTML Forms
• new kinds of input (microphones, cameras,
  scanners, pen-based, etc)
• regional variations for currency, phone numbers,
  dates, and postal addresses
• Rapid growth
• Standardization

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XML - Extensible Mark-up Language

• Ratified in 1998 - very important standard
  mark-up language - a simplified SGML.
• Developed to represent textual information in a
  structured manner that could be read and
  interpreted by a computer.
• A foundation for web services and grid services.

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Some key aspects of XML

• Tags always used in pairs delineate information
  to make it easy to process. (There is an
  exception, when the body between the tags holds
  nothing.)
• Tags can be nested. They can have attributes.
• The names of tags can be defined broadly at
  will. (In HTML, tags are predefined.)

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XML - The Extensible Markup Language

• XML is a method for putting structured data in a
  text file (enables data sharing over the Web).
• XML looks a bit like HTML but isn't HTML.
• XML is text, but isn't meant to be read.
• XML is a family of technologies.
• XML is verbose, but that is not a problem.
• XML is new, but not that new.
• XML is license-free, platform-independent and
  well-supported.

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What does XML look like?

• Traditional HTML
• ltulgt
• ltligt Vetter, R., Ward, D., and Lugo, G.
  ltemgtH/PCs Ignore the Hypelt/emgt,
• RDG Publishing Inc., 2003. lt/ligt
• lt/ulgt

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What does XML look like?

• XML
• ltBookgt
• ltAuthorgtVetter, R.lt/Authorgt
• ltAuthorgtWard, D.lt/Authorgt
• ltAuthorgtLugo, G.lt/Authorgt
• ltTitlegtH/PCs Ignore the Hypelt/Titlegt
• ltPublishergtRDG Publishing Inc.lt/Publishergt
• ltYeargt2003lt/Yeargt
• lt/Bookgt
• Note HTML is layout-oriented, while XML is
• structure-oriented.

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Example A Bibliography Entry

• lt?xml version1.0 encodingUTF-8?gt
• lt!DOCTYPE Document SYSTEM bibliography.dtdgt
• lt!- This is an example bibliography. -gt
• ltBIBgt
• ltBOOK nicknameMade-up bookgt
• ltAUTHOR idvettergtVetter, R.lt/AUTHORgt
• ltAUTHOR idwardgtWard, D.lt/AUTHORgt
• ltAUTHOR idlugogtLugo, G.lt/AUTHORgt
• ltTITLEgtH/PCs Ignore the Hypelt/TITLEgt
• ltPUBLISHERgtRDG Publishing, Inc.lt/PUBLISHERgt
• ltYEARgt2003lt/YEARgt
• lt/BOOKgt
• ltBOOK nicknameMy Second Bookgt
• ltAUTHOR idrefvetter/gtltTITLEgt lt/TITLEgt
• lt/BOOKgt
• lt/BIBgt

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A DTD for the Bibliography Example

• lt!DOCTYPE bib
• lt!ELEMENT BIB (BOOK)gt
• lt!ELEMENT BOOK (AUTHOR, TITLE, PUBLISHER?,
  YEAR?)gt
• lt!ATTLIST BOOK
• isbn CDATA IMPLIED
• nickname CDATA IMPLIEDgt
• lt!ELEMENT AUTHOR (PCDATA)gt
• lt!ATTLIST AUTHOR
• id ID IMPLIED
• idref IDREF IMPLIEDgt
• lt!ELEMENT TITLE (PCDATA)gt
• lt!ELEMENT PUBLISHER (PCDATA)gt
• lt!ELEMENT YEAR (PCDATA)gt
• gt
• Note A DTD defines a grammar
  for documents.

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XML Schema for the Bibliography Example

• ltxsdschema xmlnsxsdhttp//www.w3c.org/1999/XMLS
  chemagt
• ltxsdelement nameBOOK typeBOOK_TYPE/gt
• ltxsdcomplexType nameBOOK_TYPEgt
• ltxsdelement nameAUTHOR typexsdstring
• minOccurs1 maxOccursunbounded/gt
• ltxsdelement nameTITLE typexsdstring/gt
• ltxsdelement namePUBLISHER
  typexsdstring
• minOccurs0 maxOccurs1/gt
• ltxsdelement nameYEAR typexsddecimal
• minOccurs0 maxOccurs1/gt
• ltxsdattribute nameisbn typexsdstring/gt
• ltxsdattribute namenickname
  typexsdstring/gt
• lt/xsdcomplexTypegt
• lt/xsdschemagt
• Note A XML Schema defines a grammar for
  documents.

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XML.ORG Registry

• An open repository of hundreds of industry schema
  definitions (e.g., financial services,
  healthcare, construction, retail, insurance, real
  estate, etc.)
• See http//www.xml.org/xml/registry.jsp

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Evolution to the Object Web
Client-Side versus Server-Side Programming

• On the Client
• Javascript, ActiveX Controls, Java Applets
• On the Server
• Perl, C, Unix Shell, Java Servlets, Active Server
  Pages (ASP), Coldfusion, Java Server Pages (JSP),
  XML Server Pages (XSP), and other proprietary
  languages (e.g., Lotus Dominos scripting
  language).

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Evolution to the Object Web

• Static Web Pages HTML
• Web Pages with CGI scripts HTML Programming
  Language X (e.g., Perl or C)
• Dynamic HTML XML CSS Programming Language X
  (e.g., Javascript) DOM
• Database-Driven Web Pages HTML Programming
  Language X ODBC/JDBC
• Web Services
• Java-Based Initiatives XML SOAP WSDL UDDI
  Java J2EE
• Microsofts .Net XML SOAP WSDL UDDI C
  .NET

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The Object Web

• The following three figures were taken from the
  article CORBA, Java, and the Object Web, by R.
  Orfali, D. Harkey, and J. Edwards, Byte
  Magazine, October 1997.
• Reference
• www.byte.com/art/9710/sec6/art3.htm

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Web Services Computing Model

• Web services enables interoperability via a set
  of open standards, which distinguishes it from
  previous network services such as Javas Remote
  Method Invocation (RMI) or Corbas Internet
  Inter-ORB Protocol (IIOP).
• Web services are platform independent.

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Web Services Computing Model

• HTTP transport
• SOAP (Simple Object Access Protocol) message
  carrying XML documents
• WSDL (Web Services Description Language) used to
  describe message syntax for invoking a service
  and its response.
• UDDI (Universal Description, Discovery and
  Integration) used as web service discovery
  mechanism.

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Simple Object Access Protocol (SOAP)

• A communication protocol for passing XML
  documents. Provides mechanisms for
• Defining communication unit - a SOAP message
• Error handling
• Extensions
• Data representation
• Remote Procedure Calls
• Document-centric approach for business
  transactions
• Binding to HTTP

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Web Service Description Language (WSDL)

• A W3C standard XML document that describes three
  fundamental properties of a service
• What it is - operations (methods) it provides.
• How it is accessed - data format, protocols.
• Where it is located - protocol specific network
  address.

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Universal Description, Discovery, and Integration
(UDDI)

• UDDI is the name of a group of web-based
  registries that expose information about a
  business or other entity and its technical
  interfaces (or APIs).
• These registries are run by multiple Operator
  Sites, and can be used by anyone who wants to
  make information available about one or more
  businesses or entities, as well as anyone that
  wants to find that information.

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Web Services Computing Model

• Client needs to
• Identify the location of the required service.
• Know how to communicate with the service to get
  it to provide the actions required.
• Uses service registry - a third party.

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Service-Oriented Architecture

• Steps
• Services published in a Service registry.
• Service requestor asks Service Registry to locate
  service.
• Service requestor binds with service provider
  to invoke service.

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Service-Oriented Architecture
Service registry
1. Publish
2. Find
3. Bind
Service requester
Service provider
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Web Services Computing Model
1
2
3
4
5
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From http//www.globus.org
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Hosting Environments for Web Services

• Microsoft .NET
• IBM Websphere
• Apache Axis - http//xml.apache.org/axis

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Concluding Remarks

• The Web is moving from providing simple file
  services to interactive client-server
  applications.
• XML, SOAP, WSDL, UDDI, Java, C, EJB, and .NET
  are the emerging technologies of the Web.
• The complete Object Web involves an incredible
  mix of products and protocols.

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References

• http//www.w3c.org
• http//www.microsoft.com/net/
• http//www.webdeveloper.com
• http//www.w3.org/TR/wsdl
• http//www-3.ibm.com/services/uddi/
• http//www.w3.org/TR/SOAP/
• This PowerPoint presentation is located at
• http//people.uncw.edu/vetterr/acm2004.ppt