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Deploying New Web Technologies

Deploying New Web Technologies. Brian Kelly Email Address UK Web Focus B.Kelly@ukoln.ac.uk UKOLN URL University of Bath http://www.ukoln.ac.uk/.

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Deploying New Web Technologies

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  1. Deploying New Web Technologies 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.

  2. 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

  3. Web and Standardisation 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 • UK membersinclude JISC,UKERNA,Southampton andBristol 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" PNG HTML HTTP HTTP URN

  4. The Web Vision • Tim 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>

  5. Data Format HTML Addressing URL Web Protocols • Web initially based on three simple protocols: • Data FormatsHTML (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 Transport HTTP

  6. HTML History Dilemna Proprietary extensions cause problems. But experiments are needed • HTML 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 recommendation 1992 1994 1994-5 1995 1997 1998

  7. HTML 4.0, CSS 2.0 and DOM • HTML 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 • DOM : W3C-Rec • Document Object Model • Hooks for scripting languages • Permits changes to HTML & CSS properties and content (DHTML) • CSS Problems • Changes during CSS development • Netscape & IE incompatibilities • Continued use of browsers with known bugs

  8. 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) 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

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

  10. XML Deployment • Ariadne 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/

  11. England France 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.Interesting IPR issues! • XSL stylesheet language will provide extensibility and transformation facilities (e.g. create a table of contents) <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>

  12. Addressing • URLs (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)

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

  14. Transport • HTTP/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)

  15. URNs, DOIs AddressingURL Metadata / RDFPICS, TCN, MCF, DSig, DC,... TransportHTTP Data formatHTML HTML 4.0, CSS, XML HTTP/1.1, HTTP/NG 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

  16. 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

  17. 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 • 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

  18. Browser Support for RDF Trusted 3rd Party Metadata • 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. Embedded Metadata e.g. sitemaps Image fromhttp://purl.oclc.org/net/eric/talks/www7/devday/

  19. Deployment Issues • Various interesting new technologies have been outlined • How can they be deployed in our environment? • Should we: • Ignore them? • Accept them fully? • Accept them partly?

  20. Ignore New Developments • We 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

  21. Fully Accept New Developments • Can 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

  22. Implement "Safe" Solutions • An 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 specification Note See <URL: www.webreview.com/guides/style/insafegrid.htm> for unsafe CSS 2.0 properties

  23. Decision Time • Which would you opt for? Stick with current technologies Cheap, default option. Continuation of performance and accessibility problems. Unlikely to be long term solution. Deploy new technologies More expensive option. Functionality, performance and accessibility benefits. Access problems for old browsers. Use "safe" new technologies May require home-grown tools and support. Avoids some of the problems of other solutions

  24. An Alternative • An 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"

  25. Intelligent Server Software • Simple 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 information • This is referred to as browser-sniffing or user-agent negotiation • Note that server support is now available in Apache and in server add-ons such as PHP/FI and MS Active Server Pages (ASP)

  26. W3C CSS Gallery • W3C 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 {font-family: Tahoma, ... font-size-adjust: .53; margin-top: 1.33em; font-weight: 500; ...} H1, H2, H3, H4, H5, H6, .. {color: black; background: white} Portion of CSS file for Netscape Total 169 lines Portion of CSS file for IE Total 797 lines

  27. Java Intermediaries • Netscape and Internet Explorer don't support MathML • Who cares? MathML Java renderers are available • This 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/

  28. Deploying URNs • Problem 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

  29. Intermediaries • Intermediaries: • 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/>

  30. Web Applications • An 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

  31. Examples http://www.ukoln.ac.uk/web-focus/webwatch/services/url-info/ • Examples 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://wheel.compose.cs.cmu.edu:8001/cgi-bin/browse/objweb

  32. Content Negotiation • Transparent Content Negotiation (TCN): • Method of deploying new formats Client: 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

  33. Fourth and Fifth Ways • Several 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/>

  34. Conclusions • To 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

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