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Standards For Building Web Sites

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XLink, XPointer and XSL. XLink will provide sophisticated. hyperlinking ... XSL stylesheet language will provide extensibility and transformation facilities ... – PowerPoint PPT presentation

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Title: Standards For Building Web Sites


1
Standards For Building Web Sites
  • Brian Kelly Email Address
  • UK Web Focus B.Kelly_at_ukoln.ac.uk
  • UKOLN
  • University of Bath
  • http//www.ukoln.ac.uk/

UKOLN is funded by Resource The Council for
Museums, Archives and Libraries, the Joint
Information Systems Committee (JISC) of the
Higher Education Funding Councils, as well as by
project funding from the JISC and the European
Union. UKOLN also receives support from the
University of Bath where it is based.
2
Contents
  • Introduction
  • Web Standards Overview
  • Web Standards
  • Data Formats
  • Transport
  • Addressing
  • Metadata
  • Deployment Issues
  • Questions
  • Aims of Talk
  • To describe standards bodies involved with the
    Web
  • To review key Web standards
  • To report on developments to Web standards
  • To briefly address implementation models

3
UK Web Focus / W3C
  • UK Web Focus
  • JISC funded post based at UKOLN (Bath Univ)
  • Advises UK HE community on web issues
  • Represents JISC on W3C
  • UKOLN
  • UK Office for Library and Information Networking
  • Applied research (e.g. JISC and EU-funded
    projects) and dissemination
  • W3C (World Wide Web Consortium)
  • International consortium, with headquarters at
    MIT, INRIA and Keio University (Japan)
  • Coordinates development of web protocols and
    file formats

4
Standards, Architectures, Applications, Resources
  • This talk is concerned primarily with the
    standards used to develop web services

Architectures models for implementing systems
Standards concerned with protocols and file
formats
NT / Unix File system / database application HTML
tools / content management
Open standards vs. Proprietary HTML / XML vs.
PDF CSS / XSL vs. HTML
Applications software products used to implement
systems
Resources financial and staff costs needed to
implement systems
Apache / IIS FrontPage / Dreamweaver Oracle /
SQLServer
Development vs. Migration costs Use of in-house
expertise In-house vs. out-sourced Licensed vs.
open source
5
Standards
  • Need for standards to provide
  • Platform independence
  • Application independence
  • Avoidance of patented technologies
  • Flexibility ("evolvability" - Tim Berners-Lee)
  • Architectural integrity
  • Long-term access to data
  • Ideally look at standards first, then find
    applications which support the standards
  • Difficult to achieve this ideal!

6
Standardisation
  • Other
  • Standards bodies such as ECMA
  • Community groups which can agree on, say, profiles

HTML extensions PDF and Java?
  • Proprietary
  • De facto standards
  • Often initially appealing (cf PowerPoint)
  • May emerge as standards
  • W3C
  • Produces W3C Recommendations on Web protocols
  • Managed approach to developments
  • Protocols initially developed by W3C members
  • Decisions made by W3C, influenced by member and
    public review

PNG HTML Z39.50 Java?
  • ISO
  • Produces ISO Standards
  • Can be slow moving and bureaucratic
  • Produce robust standards
  • IETF
  • Produces Internet Drafts on Internet protocols
  • Bottom-up approach to developments
  • Protocols developed by interested individuals
  • "Rough consensus and working code"

HTTP URN whois
PNG HTML HTTP
7
The Web Vision
  • Tim Berners-Lee's vision for the Web
  • Automation of information management If a
    decision can be made by machine, it should
  • All structured data formats should be based on
    XML
  • Migrate HTML to XML
  • All logical assertions to map onto RDF model
  • All metadata to use RDF

A useful overview of Tim Berners-Lee's vision for
the Web is given in his book Weaving The Web.
8
Web Protocols
  • Web initially based on three simple protocols
  • Data Formats HTML (HyperText Markup Language)
    provides the data format for native documents
  • Addressing URLs (Uniform Resource Locator)
    provides an addressing mechanism for web
    resources
  • Transport HTTP (HyperText Transfer Protocol)
    defines transfer of resources between client and
    server

Transport HTTP
9
HTML History
  • HTML 1.0 Unpublished specification. DTD
    developed by Tim Berners-Lee (CERN).
  • HTML 2.0 Spec. based on innovations from NCSA
    (forms and inline images!)
  • HTML 3.0 Proposed spec. (renamed from
    HTML). Very comprehensive Failed to complete
    IETF standardisation Little implementation
    experience
  • Proprietary Introduction of proprietary HTML
    elements by Netscape and Microsoft (browser wars)
  • HTML 3.2 Spec. based on description of mainstream
    innovations in marketplace
  • HTML 4.0 Current recommendation

10
Problems with Extensions
  • Device Dependency
  • Resources are dependent on a particular browser
  • Platform dependency
  • Costs
  • Read costs in supporting multiple architectures
  • Potential costs in re-engineering
  • Architecture
  • Proprietary innovations have been flawed
  • Merging content and appearance
  • Maintenance of resources
  • Accessibility problems
  • Poor support for access by disabled
  • But
  • Experiments are needed

11
HTML 4.0, CSS 2.0 and DOM
  • HTML 4.0 used in conjunction with CSS 2.0
    (Cascading Style Sheets) and DOM 1.0 provides an
    architecturally pure, yet functionally rich
    environment
  • HTML 4.0
  • Improved forms
  • Hooks for stylesheets
  • Hooks for scripting languages
  • Table enhancements
  • Better printing
  • CSS 2.0
  • Support for all HTML formatting
  • Positioning of HTML elements
  • Multiple media support
  • DOM 1.0
  • Document Object Model
  • Hooks for scripting languages
  • Permits changes to HTML CSS properties and
    content
  • CSS Problems
  • Changes during CSS development
  • Netscape IE incompatibilities
  • Continued use of browsers with known bugs

12
HTML Limitations
  • HTML 4.0 / CSS 2.0 have limitations
  • Difficulties in introducing new elements
  • Time-consuming standardisation process (ltABBREVgt)
  • Dictated by browser vendor (ltBLINKgt, ltMARQUEEgt)
  • Area may be inappropriate for standarisation
  • Covers specialist area (maths, music, ...)
  • Application-specific (ltSTUD-NUMgt)
  • HTML is a display (output) format
  • HTML's lack of arbitrary structure limits
    functionality
  • Find all memos copied to John Smith
  • How many unique tracks on Jackson Browne CDs

13
XML
  • XML
  • Extensible Markup Language
  • A lightweight SGML designed for network use
  • Addresses HTML's lack of evolvability
  • Arbitrary elements can be defined
    (ltSTUDENT-NUMBERgt, ltPART-NOgt, etc)
  • Agreement achieved quickly - XML 1.0 became W3C
    Recommendation in Feb 1998
  • Support from industry (SGML vendors, Microsoft,
    etc.)
  • Support in Netscape 6 (?) and IE 5

14
XML Concepts
  • Well-formed XML resources
  • Make end-tags explicit ltligt...lt/ligt
  • Make empty elements explicit ltimg ... /gt
  • Quote attributes ltimg src"logo.gif" height"20"
  • Use consistent upper/lower case
  • Valid XML resources
  • Need DTD
  • XML Namespaces
  • Mechanism for ensuring unique XML elements
  • lt?xmlnamespace ns"http//foo.org/ 1998-001"
    prefix"i"gt
  • ltpgtInsert ltiPARTgtM-471lt/iPARTgtlt/pgt

15
XLink, XPointer and XSL
  • XLink will provide sophisticated hyperlinking
    missing in HTML
  • Links that lead user to multiple destinations
  • Bidirectional links
  • Links with special behaviors
  • Expand-in-place / Replace / Create new window
  • Link on load / Link on user action
  • Link databases
  • XPointer will provide access to arbitrary
    portions of XML resource
  • XSL stylesheet language will provide
    extensibility and transformation facilities (e.g.
    create a table of contents)

ltcommentary xmllink"extended" inline"false"gt
ltlocator href"smith2.1" role"Essay"/gt
ltlocator href"jones1.4" role"Rebuttal"/gt
ltlocator href"robin3.2" role"Comparison"/gt
lt/commentarygt
16
More XML Developments
  • Momentum behind XML is driving additional
    standardisation developments
  • XML Path A language for addressing parts of an
    XML document, designed to be used by XSLT and
    XPointer
  • XML Schemas (Ii) Defining the nature of XML
    schemas and their component parts
  • XML Schemas (II) Facilities for defining
    datatypes to be used in XML Schemas and other XML
    specifications
  • XSLT A language for transforming XML documents
    into other XML documents
  • XML Infospace An abstract data set containing the
    information available from an XML document

17
XHTML
  • XHTML
  • Extensible Hypertext Markup Language
  • HTML represented in XML
  • Some small changes to HTML
  • Elements in lowercase (ltpgt not ltPgt)
  • Attributes must be quoted (ltimg src"logo"
    height"50"gt
  • Elements must be closed (ltpgt..lt/pgt)
  • Empty elements must be closed (ltimg src"logo" ..
    /gt)
  • Gain benefits from XML
  • Tools available (e.g. HTML-Kit from
    http//www.chami.com/html-kit/)
  • See lthttp//www.webreference.com/xml/ column6/gt
    and lthttp//www.builder.com/ Authoring/Xhtml/gt

18
Addressing
  • URLs (e.g. http//www.bristol-poly .ac.uk/depts/mu
    sic/) have limitations
  • Lack of long-term persistency
  • Organisation changes name
  • Department scrapped
  • Directory structure reorganised
  • Inability to support multiple versions of
    resources (mirroring)
  • URNs (Uniform Resource Names)
  • Proposed as solution
  • Difficult to implement (no W3C activity in this
    area)

19
Addressing - Solutions
  • DOIs (Document Object Identifiers)
  • Proposed by publishing industry as a solution
  • Aimed at supporting rights ownership
  • Business model needed
  • PURLs (Persistent URLs)
  • Provide single level of redirection
  • Cache support
  • National caches could provide simple URN support
  • For further information see
  • ltURL http//www.ukoln.ac.uk/metadata/ resources/u
    rn/gt
  • ltURL http//hosted.ukoln.ac.uk/biblink/ wp2/links
    .htmlgt

20
Transport
  • HTTP/0.9 and HTTP/1.0
  • Made the Web popular
  • Design flaws and implementation problems caused
    poor performance
  • HTTP/1.1
  • Addresses some of these problems
  • 60 server support, client proxy support
    beginning
  • Performance benefits! (optimised implementation
    reduces packet traffic by 2/3)
  • Is acting as fire-fighter
  • Poor usage counting
  • Not sufficiently flexible or extensible

21
HTTP/NG
  • HTTP/NG
  • Ideas for next generation of HTTP
  • Produced various studies and reports
  • No longer being developed within W3C
  • Work now being coordinated by the IETF

22
Metadata
  • Metadata - the missing architectural component
    from the initial implementation of the web
  • Metadata Needs
  • Resource discovery
  • Content filtering
  • Authentication
  • Improved navigation
  • Multiple format support
  • Rights management

23
Privacy
  • P3P (Platform for Privacy Preferences)
  • Example of a metadata application
  • Privacy concerns are a current barrier to Web
    development (esp. in US)
  • P3P project developing methods for exchanging
    Privacy Practices of Web sites and user
  • Documents on architecture and vocabulary
    available
  • See ltURL http//www.w3.org/TR/P3P/gt

24
Digital Signatures
  • DSig (Digital Signatures initiative)
  • Key component for providing trust on the web
  • DSig 1.0 is based on PICS
  • DSig 2.0 will be based on RDF and will support
    signed assertion
  • This page is from the University of Bath
  • This page is a legally-binding list of courses
    provided by the University
  • See lthttp//www.w3.org/DSig/gt

25
RDF
  • RDF (Resource Description Framework)
  • Highlight of WWW 7 conference
  • Provides a metadata framework ("machine
    understandable metadata for the web")
  • Based on ideas from content rating (PICS),
    resource discovery (Dublin Core) and site mapping
    (MCF)
  • Applications include
  • cataloging resources resource discovery
  • electronic commerce intelligent agents
  • digital signatures content rating
  • intellectual property rights privacy
  • See ltURL http//www.w3.org/RDF/gt

26
RDF Model
RDF Data Model
  • RDF
  • Based on a formal data model (direct label
    graphs)
  • Syntax for interchange of data
  • Schema model

PropertyType
Resource
Value
Property
page.html
Cost
0.05
Cost
ValidUntil
page.html
0.05
11-May-98
PropObj
InstanceOf
Value
Property
ValidUntil
PropName
11-May-98
Cost
27
RDF Example
  • Example of Dublin Core metadata in RDF

ltRDF xmlns"http//www.w3.org/1999/02/22-rdf-synta
x-ns" xmlnsDC"http//purl.org/dc/elements/1.0/"
gt ltDescription about"http//www.w3.org/folio.html
"gt ltDCtitlegtThe W3C Folio 1999lt/DCtitlegt ltDCcre
atorgtW3C Communications Teamlt/DCcreatorgt ltDCdate
gt1999-03-10lt/DCdategt ltDCsubjectgtWeb
development, World Wide Web Consortium,
Interoperability of the Weblt/DCsubjectgt lt/Descrip
tiongt lt/RDFgt
See lthttp//www.w3.org/Metadata/Activity/gt
RDF has been used to express data about the W3C
Folio. The basic concept is that metadata about
this item on the Web is described through a
collection of properties called an RDF
Description. Notice that RDF uses the familiar
XML syntax. This example also illustrates XML
Namespaces.
28
RDF Conclusion
  • RDF is a general-purpose framework
  • RDF provides structured, machine-understandable
    metadata for the Web
  • Metadata vocabularies can be developed without
    central coordination
  • RDF Schemas describe the meaning of each property
    name
  • Signed RDF is the basis for trust

29
Deployment Issues
  • What part of the spectrum are you closest to?

Must support standards
Go with the marketplace
30
I Support Standards
  • But
  • You probably use PowerPoint, don't you?
  • Software vendors will subtly suck you into use of
    proprietary features
  • Home-grown solutions can be expensive (where are
    all the good Perl / C programmers willing to work
    on short-term contracts for a pittance in
    Universities?)
  • Standards may not take off remember Coloured
    Book network protocols?
  • Proprietary solutions may become standardised
  • Standards may not yet be available (or finalised)
  • Do users want standards? Will "We support
    standards" conflict with "Our services are based
    on user requirements"?

31
I Follow The Marketplace
  • Good New Labour philosophy, but
  • Can you trust your software vendor?
  • Will your software vendor be around in a few
    years time ("I only buy Rover")
  • Will your system be interoperable?
  • What happens when you want to interwork with
    partners or your organisation merges / is taken
    over?
  • What happens when you want to extend your system
    beyond the limits set by your software vendor?

32
Some Difficulties
  • We should acknowledge some difficulties in a
    standards-based approach
  • Keeping up-to-date (look at nos. of documents at
    http//www.w3c.org/TR/ and size of
    http//www.diffuse.org/standards.html)
  • Spotting the winning standards
  • Implementing the standard in a timely way
  • Dealing with the problems of the software vendor
  • Resources!

33
Is It Worth It?
  • Has the Web stabilised?
  • Are you thinking about WAP services?
  • Will you want to (be forced to) make your web
    service accessible?
  • Will you want to deploy personalised interfaces
    (e.g. My.Oxford.ac.uk)
  • Will your web service move from information
    provision to e-business?
  • Do you want your University web site to use
    business-to-business (B2B) protocols to automate
    transfer of link and news items to HERO (neé HE
    Mall)?

34
What Should I Do?
  • What approaches should I use?
  • Storing information in a structured format makes
    subsequent redevelopment easier
  • Be driven initially by standards and
    architectural considerations, not by applications
  • Consider use of more sophisticated web management
    tools, rather than HTML authoring tools
  • An organisational standards guidelines document
    (part of a Web Strategy document) may be useful
  • Don't work in isolation
  • Monitor standards development (e.g. W3C)
  • Listen to others in your community
  • Talk and discuss issues within your community

35
Architectural Models
  • There is a need for more intelligent software
    which can process structured resources or
    reformat unstructured ones

Web server simply sends file to client File
contains redundant information (for old browsers)
plus client interrogation support
HTML resource
Web server
HTML / XML / database resource
Intelligent Web server
Client proxy
Server proxy
  • Intermediaries can provide functionality not
    available at client
  • DOI support
  • XML support
  • Format conversion

36
Architectural Models e.g. XML Deployment
  • Ariadne issue 14 has article on "What Is XML?"
  • Describes how XML support can be provided
  • Natively by new browsers
  • Back end conversion of XML - HTML
  • Client-side conversion of XML - HTML / CSS
  • Java rendering of XML
  • Examples of intermediaries

See http//www.ariadne.ac.uk/issue15/what-is/
37
Conclusions
  • To conclude
  • Standards are important, especially for large
    organisation and national initiatives
  • Proprietary solutions are often tempting because
  • They are available
  • They are often well-marketed and well-supported
  • They may become standardised
  • Solutions based on standards may not be properly
    supported by applications
  • Intermediaries may have a role to play in
    deploying standards-based solutions

38
Further Information
  • W3C web site lthttp//www.w3.org/gt
  • W3C Tech Reports lthttp//www.w3.org/TR/gt
  • "The Development Of Web Protocols And
  • Formats", Exploit Interactive issue 1,
    lthttp//www.exploit-lib.org/issue1/web/gt
  • "Wilde's WWW Technical Foundations of the World
    Wide Web", Erik Wilde, ISBN 3-540-64285-4
  • Diffuse Project web site lthttp//www.diffuse.org
    /gt
  • "On Julius Caesar, Queen Eanfleda, and the
    lessons from time past" Brian Meek, KCL
    lthttp//www.kcl.ac.uk/kis/support/cc/staff/ brian/
    caesar.htmlgt

39
Community Information
  • Discuss standards, architectures and applications
    on various mailing lists
  • website-info-mgt Mailbase list
  • web-support Mailbase list
  • See lthttp//www.mailbase.ac.uk/gt
  • Participate in the Institutional Web Management
    workshop (Bath University, 7-9th Sept) details
    will be announced on website-info-mgt Mailbase
    list

40
Question Time
  • Any questions?
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