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Web Standards

Brian Kelly Email Address

UK Web Focus B.Kelly@ukoln.ac.uk

UKOLN URL

University of Bath http://www.ukoln.ac.uk/

UKOLN is funded by the British Library Research and Innovation Centre, the Joint Information Systems Committee of the Higher Education Funding Councils, as well as by project funding from the JISC’s Electronic Libraries Programme and the European Union. UKOLN also receives support from the University of Bath where it is based.

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Contents

• Introduction

• Web Standards Overview

• Web Standards:• Data Formats• Transport• Addressing

• Metadata

• Distributed Searching

• Deployment Issues

Aims of Talk• To give brief overview

of web architecture• To describe

developments to web standards

• To briefly address implementation models

Aims of Talk• To give brief overview

of web architecture• To describe

developments to web standards

• To briefly address implementation models

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About UK Web Focus

UK Web Focus:

• JISC-funded post

• Advises UK HE community on web developments

• Represents JISC on World Wide Web Consortium (W3C)

• Organises events (e.g. national web managers workshop)

• Dissemination of information (e.g. see Web Focus column in Ariadne - http://www.ariadne.ac.uk/)

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Why Care About Standards?

This talk covers development of web standards, not web applications

An understanding of web standards is needed:• To appreciate when solutions are proprietary• To provide flexibility and interoperability• To avoid developing home-grown application solutions, when

protocol solutions are in the offing

The seminar is aimed at:• Web applications developers (e.g. CBL)• Developers of components of the Distributed National

Electronic Resource (DNER)• Web researchers• Other interested parties

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Standardisation

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

IETF• Produces Internet

Drafts on Internet protocols• Bottom-up approach to developments• Protocols developed by

interested individuals• "Rough consensus and working

code"

ISO• Produces ISO

Standards• Can be slow moving

and bureaucratic• Produce robust

standards

Proprietary• De facto standards• Often initially appealing

(cf PowerPoint, PDF)• May emerge as

standards

PNGHTMLZ39.50Java?

PNGHTMLZ39.50Java?

PNGHTMLHTTP

PNGHTMLHTTP

HTTPURNwhois++

HTTPURNwhois++

HTML extensionsPDF and Java?

HTML extensionsPDF and Java?

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The Web Vision

Tim Berners-Lee's vision for the Web:• Evolvability is critical • 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

See keynote talk at WWW 7 conference at <URL: http://www.w3.org/Talks/1998/0415-Evolvability/slide1-1.htm>

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HTML 4.0, CSS 2.0 and DOMHTML 4.0 used in conjunction with CSS 2.0 (Cascading Style Sheets) and the DOM provides an architecturally pure, yet functionally rich environment

HTML 4.0 - W3C-Rec• Improved forms• Hooks for stylesheets• Hooks for scripting

languages• Table enhancements• Better printing

CSS 2.0 - W3C-Rec• Support for all HTML

formatting • Positioning of HTML

elements• Multiple media support

Problems• Changes during CSS development• Netscape & IE incompatibilities • Continued use of browsers with

known bugs

Problems• Changes during CSS development• Netscape & IE incompatibilities • Continued use of browsers with

known bugs

DOM - W3C-Rec• Document Object Model• Hooks for scripting

languages• Permits changes to

HTML & CSS properties and content

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HTML Limitations

HTML 4.0 / CSS 2.0 have limitations:• Difficulties in introducing new elements

– Time-consuming standardisation process (<ABBREV>)

– Dictated by browser vendor (<BLINK>, <MARQUEE>)

• Area may be inappropriate for standarisation:– Covers specialist area (maths, music, ...)– Application-specific (<STUD-NUM>)

• 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

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XML

XML:• Extensible Markup Language• A lightweight SGML designed for network use• Addresses HTML's lack of evolvability• Arbitrary elements can be defined (<STUDENT-NUMBER>, <PART-NO>, etc)

• Agreement achieved quickly - XML 1.0 became W3C Recommendation in Feb 1998

• Support from industry (SGML vendors, Microsoft, etc.)

• Support in Netscape 5 and IE 5

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XML Deployment

Ariadne issue 15 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/See http://www.ariadne.ac.uk/issue15/what-is/

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XLink, XPointer and XSL

XLink will provide sophisticated hyperlinking missing in HTML:

• Links that lead user to multiple destinations• Bidirectional links• Links with special behaviours:

– 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)

EnglandFrance

<commentary xml:link="extended" inline="false"> <locator href="smith2.1" role="Essay"/> <locator href="jones1.4" role="Rebuttal"/> <locator href="robin3.2" role="Comparison"/> </commentary>

<commentary xml:link="extended" inline="false"> <locator href="smith2.1" role="Essay"/> <locator href="jones1.4" role="Rebuttal"/> <locator href="robin3.2" role="Comparison"/> </commentary>

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XML Update

Data / SchemasXML-Data: Submitted to W3C Jan 98 (Obsolete?)Document Content Description: Submitted Aug 98XSchema: Independent effort

Programming InterfaceDOM level 1: W3C Recommendation, May 98

Style & PresentationCSS level 2: W3C Recommendation, May 98Extensible Style Language: Working Draft, Aug 98

Relationship to Other ResourcesXLink , XPointer: Working Drafts, Mar 98XML Namespaces: Working Draft, Aug 98

Query LanguagesXML Query Language: Submitted to W3C Aug 98XQL: Independent effort

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Addressing

URLs (e.g. http://www.bristol-poly.ac.uk/depts/music/) have limitations:

• Lack of long-term persistency– Organisation changes name– Department shut down or merged– 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)

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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

Pragmatic Solution:• URLs don't break - people break them• Design URLs to have long life-span

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TransportHTTP/0.9 and HTTP/1.0:

Design flaws and implementation problems

HTTP/1.1: Addresses some of these problems 60% server support Performance benefits! (60% packet traffic reduction) Is acting as fire-fighter Not sufficiently flexible or extensible

HTTP/NG: Radical redesign using object-oriented technologies Undergoing trials Gradual transition (using proxies) Integration of application (distributed searching?)

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MetadataMetadata - the missing architectural component from the initial implementation of the web

Metadata - RDF

PICS, TCN,

MCF, DSig,

DC,...

AddressingURL

Data formatHTML

TransportHTTP

Metadata Needs:• Resource discovery• Content filtering• Authentication• Improved navigation• Multiple format support• Rights management

Metadata Needs:• Resource discovery• Content filtering• Authentication• Improved navigation• Multiple format support• Rights management

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Metadata Examples

DSig (Digital Signatures initiative):• Key component for providing trust on the web• 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

P3P (Platform for Privacy Preferences):• Developing methods for exchanging Privacy Practices

of Web sites and user

Note that discussions about additional rights management metadata are currently taking place

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Sitemaps

Sitemaps provide navigational alternatives to browsing a site by following links.

Configurable site maps will enable end users to define hierarchies

http://www.elsop.com/linkscan/map.html

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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 <URL: http://www.w3.org/Talks/1998/0417-WWW7-RDF>

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RDF ModelRDF:

• Based on a formal data model (direct label graphs)

• Syntax for interchange of data

• Schema model

Resource ValuePropertyType

Property

page.html £0.05Cost

11-May-98

ValidUntil

RDF Data Model

page.html £0.05

11-May-98

Property

Cost

InstanceOf

ValidUntil

ValuePropObj

Cost

PropName

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Browser Support for RDF

Mozilla (Netscape's source code release) provides support for RDF.

Mozilla supports site maps in RDF, as well as bookmarks and history lists

See Netscape's or HotWired home page for a link to the RDF file.

Trusted 3rd

Party Metadata

Embedded Metadata

e.g. sitemaps

Image from http://purl.oclc.org/net/eric/talks/www7/devday/Image from http://purl.oclc.org/net/eric/talks/www7/devday/

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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

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Distributed SearchingDistributed searching important for the DNER (Distributed National Electronic Resource)

ROADS prototype provides cross-searching using whois++

ROADS prototype provides cross-searching using whois++

AHDS prototype provides cross-searching using Z39.50

AHDS prototype provides cross-searching using Z39.50

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Distributed Searching Issues

Providing access to resources by software rather than by humans raises several issues:• Loss of service visibility / value-added web services• Possible performance problems• Information overload• Finding the service

Solutions:• Giving visibility and pointers in results sets• Service metadata:

–Service only available for cross-searching by non AC.UK users outside peak hours

• Need for agreed metadata standards (profiles, rights issues, …)

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Deployment Issues

How can new technologies be deployed?• Expect (hope) everyone will move to new

browsers• Use technologies in backwards-compatible

manner• Develop additional protocols e.g.

– Transparent Content Negotiation– CC/PP (see http://www.w3.org/TR/NOTE-CCPP)

• User-agent negotiation• Use of proxy intermediaries

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Intermediaries can provide functionality not available at client:

• DOI support• XML support / format conversion• Authentication

Intermediaries can provide functionality not available at client:

• DOI support• XML support / format conversion• Authentication

Deployment IssuesMore sophisticated deployment techniques can be adopted to overcome deficiencies in simple model

HTML resource

browserWeb server

Web server simply sends file to clientFile contains redundant information (for old browsers) plus client interrogation support

HTML / XML /

databaseresource browser

Server proxy

Client proxy

Original Model

Sophisticated Model

IntelligentWeb server

Example of an intermediary

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Conclusions

To conclude:• Standards are important, especially for national

initiatives and other large-scale services• 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

• Metadata is big growth area• Intermediaries (brokers) likely to have a key role to

play in deploying standards-based solutions• Intelligent servers likely to be important