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Deploying New Web Technologies

Brian Kelly Email AddressUK Web Focus B.Kelly@ukoln.ac.ukUKOLN URLUniversity 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• Background• Web Developments:

• Data Formats• Transport• Addressing• Metadata

• Deployment Issues• Questions

Aims of Talk• To give an overview of

the Web architecture and Web standardisation

• To review new web developments

• To address implementation models

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Web and 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

•UK membersinclude JISC,UKERNA,Southampton andBristol

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)• May emerge as

standards

PNGHTMLZ39.50Java?

PNGHTMLHTTP

HTTPURN

HTML extensionsPDF and Java?

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The Web VisionTim Berners-Lee's (and W3C'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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Web ProtocolsWeb initially based on three simple protocols:• Data Formats

HTML (HyperText Markup Language) provides the data format for native documents

• AddressingURLs (Uniform Resource Locator) provides an addressing mechanism for web resources

• TransportHTTP (HyperText Transfer Protocol) defines transfer of resources between client and server

Data FormatHTML

AddressingURL

TransportHTTP

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HTML HistoryHTML 1.0 Unpublished specification. 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

HTML 3.2 Spec. based on description of mainstream innovations in marketplace

HTML 4.0 Current recommendation1998

1994

1997

1994-5

1995

1992

DilemnaProprietary extensions

cause problems.But experiments

are needed

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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

CSS 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 (DHTML)

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HTML LimitationsHTML 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) not storage 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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XMLXML:

• 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.)• Various XML DTDs already agreed (MathML, CML)• Support in Netscape 5 and IE 5

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XML DeploymentAriadne issue 14 has an 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/

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XLink, XPointer and XSLXLink 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 databasesXPointer will provide access to arbitrary portions of XML resource.Interesting IPR issues!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>

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AddressingURLs (e.g. http://www.bristol-poly.ac.uk/depts/music/latest.html) have limitations:• Lack of long-term persistency

– Organisation changes name– Department shut down / 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 - SolutionsDOIs (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

Further information:<URL: http://www.ukoln.ac.uk/metadata/resources/urn/><URL: http://hosted.ukoln.ac.uk/biblink/wp2/

links.html>

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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 used object-oriented technologies Undergoing trials Gradual transition (using proxies)

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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

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Metadata ExamplesDSig (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 userNote that discussions about additional rights management metadata are currently taking place

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RDFRDF (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• Based on a formal data model (direct label graphs)• Applications include:

– cataloging resources – resource discovery– electronic commerce – intelligent agents– digital signatures – content rating– intellectual property rights – privacy

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Browser Support for RDFMozilla (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/

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Deployment IssuesVarious interesting new technologies have been outlinedHow can they be deployed in our environment?Should we:

• Ignore them?

• Accept them fully?

• Accept them partly?

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Ignore New DevelopmentsWe can chose to ignore new developments, and continue to use HTML 3.2:

Safe option, with no new training, support or software costs

Experience in effectiveness, limitations, etc. Fails to address current performance problems Fails to address accessibility problems Fails to provide new functionality Service likely to look "old-fashioned" compared

with competition

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Fully Accept New DevelopmentsCan chose to more fully to, say, HTML 4.0 and CSS 2.0:

Can be exciting to be at leading edge Performance benefits Accessibility benefits Based on open-standards Provides motivation for users to upgrade browsers Likely to be solution at some point (cf. Gopher)

Backwards compatibility problems with old browsers Costly to deploy new authoring news, training, .. Likely to be bugs and incompatibilities with new tools

and browsers

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Implement "Safe" SolutionsAn alternative is to use "safe" technologies which are backwards compatible and avoid major browser bugs

Attractive sounding compromise position Lose some functionality, but not all

Can be difficult or expensive to find "safe" options (does .margin-left work on IE on SGI?)

Tools may not allow safe options to be chosen Lack of validation tools for checking conformance

with restricted set of specificationNote See <URL: www.webreview.com/guides/style/insafegrid.htm> for unsafe CSS 2.0 properties

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Decision TimeWhich would you opt for?

Stick with current technologiesCheap, default option. Continuation of performance and accessibility problems. Unlikely to be long term solution.

Deploy new technologiesMore expensive option. Functionality, performance and accessibility benefits. Access problems for old browsers.

Use "safe" new technologiesMay require home-grown tools and support. Avoids some of the problems of other solutions

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An AlternativeAn alternative approach to deploying new technologies is available:

• Use more intelligent server-side software• Use "proxies" to address limitations of

browser technologies. The term intermediary was used in a paper [1] at the WWW 7 conference to describe this approach

• Protocol solutions, such as Transparent Content Negotiation (TCN)

[1] "Intermediaries: New Places For Producing and Manipulating Web Content"

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Intelligent Server SoftwareSimple model:

• Server receives request for resource• Server delivers resource to client

More sophisticated model:• Server receives request for resource • Server processes header information from client• Server delivers resource to client based on client

informationThis is referred to as browser-sniffing or user-agent negotiationNote that server support is now available in Apache and in server add-ons such as PHP/FI and MS Active Server Pages (ASP)

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Portion of CSS file for IETotal 797 lines

W3C CSS GalleryW3C have a link to a core style sampler service.The service provides 8 core style sheets which can be freely linked to.The style sheets use "browser sniffing". Different style sheets are delivered to different browsers.

H1, H2, H3, H4, H5, H6, .. {color: black; background: white} Portion of CSS file for NetscapeTotal 169 lines

H1 {font-family: Tahoma, ... font-size-adjust: .53; margin-top: 1.33em; font-weight: 500; ...}

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Java IntermediariesNetscape and Internet Explorer don't support MathMLWho cares? MathML Java renderers are availableThis concept can be generalised to deploying support for other new markup languages.For example see the Displets work at http://www.cs.unibo.it/~fabio/displet/

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Deploying URNsProblem

Today's browsers can't process URNs, such as:urn:doi:10.1000/1

Possible Solution• A separate program could resolve URNs into URLs• Andy Powell (UKOLN) has demonstrated use of

Netscape's autoproxy to pass on URNs of the format above to Squid for resolution [1]

• Example of use of an intermediary to deploy new technologies not supported by current browsers

[1] "Resolving DOI Based URNs Using Squid" at http://mirrored.ukoln.ac.uk/lis-journals/dlib/dlib/dlib/june98/06powell.html

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IntermediariesIntermediaries:

• Enable new functionality to be introduced to the web without extending the client or the server

• Intermediaries can be implemented using proxies• Intermediaries can be used for applications such as

web personalisation, document caching, content distillation and protocol extension

• Demonstration available using WBI (Web Browser Intelligence)

• See <URL: http://wwwcssrv.almaden.ibm.com/wbi/>

• Another example for web accessibility at <URL: http://www.inf.ethz.ch/department/IS/ea/blinds/>

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Web ApplicationsAn Example

• We're familiar with HTML validation services (e.g. HENSA mirror)

• We can "go there" and use the service• We can also have a link from the page which will run

the service (rather than just go to the form)• Consider:

– Web page is in Bath– User is in Sheffield– Application is in Kent

• An example of a web (intermediary?) application

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ExamplesExamples of remote web applications include:

• Link checking• Website analysis• Document format

conversion• Accessibility support

Imagine an intermediary service which called an XML - HTML conversion service if the browser agent didn't support XML

http://www.ukoln.ac.uk/web-focus/webwatch/services/url-info/

http://wheel.compose.cs.cmu.edu:8001/cgi-bin/browse/objweb

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Content NegotiationTransparent Content Negotiation (TCN):

• Method of deploying new formatsClient:

ACCEPT image/gif, image/png

Server:If foo.png exists, send, else foo.gif

• Used for logos on W3C website• Not widely deployed

Transparent Feature Negotiation:• Proposal for deploying new HTML elements• Over-engineered? Requires naming authority

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Fourth and Fifth WaysSeveral other options for deploying new web technologies (e.g. on low spec PCs):

Run Browser on Server• Use Windows Terminal Server, Citrix, etc.• Browser runs on NT server

Deploy JavaPC (e.g. for DOS)• Use the JavaPC and run HotJava browser (min.

spec 486 PC with 8Mb)Opera

• Supports CSS, Frames, … on 486 PCs (8Mb)• See <URL: http://www.operasoftware.com/>

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ConclusionsTo conclude:• New web protocols are still being developed• Deployment of new technologies can be expensive

or time-consuming, but is likely to be needed• Various deployment models:

Don't implement Implement fully Implement via proxy Others (thin

clients, …)• We can't do it all ourselves• Experience in developing (wide-area) web

applications will help in developing intermediaries