1 Web Developments Related To Metadata Brian Kelly UK Web Focus UKOLN University of Bath

2 Contents PICS Digital Signatures XML Web Collections Other Developments Conclusions

3 Background to PICS PICS: Platform for Internet Content Selection Developed in response to concerns about pornography on Internet, especially the US Communications Decency Act Developed in response to US 1st amendment guaranteeing freedom of speech Content selection handled on client based on PICS ratings No censoring of materials - filtering managed by client managers - e.g. parent, organisation

4 PICS and Metadata What has PICS (a rating scheme) to do with metadata? Compare: "Filter all films containing excessive violence" and "Find all films containing excessive violence " Conclusions: PICS ratings are a form of metadata Is it sensible to have multiple ways of representing metadata?

5 PICS/NG Support for strings: PICS/1.1 supports numeric data: (PICS-1.1 labels on " T08: " until " T23: " for " ratings (suds 0.5 density 0 color/hue 1)) PICS/NG supports strings: author="Salmon Rushdie" Likely to be implemented in XML: PICS/1.1 has lisp-like syntax

6 Digital Signatures Trust mechanisms on Web are poor: Is it really? Can I trust them? Are these course details legally binding? Digital Signature Initiative (DSig) aims to provide a trust architecture: SignaturesThis page really is from x AssertionsThis assertion is legally binding DSig will be implemented in PICS

7 XML XML: Extensible Markup Language A lightweight implementation of SGML designed for network use Developed by SGML community Products emerging from SGML tool vendors and others "Internet Explorer version 4.0 will support a few XML applications (such as CDF). Microsoft will be supporting XML in future versions of Internet Explorer " see xml-f.htm

8 XML Applications Various XML applications are being developed: CML (Chemical Markup Language) - see /vsms/java/cml/tutorial.html MathML - see WD-math/ CDF (Channel Data Format) Home grown applications (Intranet) Various metadata-related proposals (PICS/NG, Web Collections, MCF, …)

9 Web Collections Various proprietary ways of visualising web sites are available (e.g. MAPA, WebCutter) Need a standard for defining relationships between web pages, to provide application independence get/PAPER40.html

10 Web Collections Web Collections: Defines relationships between groups of Internet resources Relationships include: Next, Previous, Glossary, Home, Parent, Sibling,... Can be used for: PrintingOff-line browsing IndexingNavigational aids... Web Collections specification being written in XML

11 MCF MCF (Meta Content Format): Developed by Apple, and now being promoted by Netscape A language for representing relationships between information on a Web site Represented using XML Application available such as HotSauce (fly-though metadata space)

12 WebDAV Web designed for collaborative authoring (many authors) Implemented as a publishing system (few authors, many readers) Need for protocol developments to facilitate application and platform independent collaborative authoring Work being carried out by IETF WebDAV (Web Distributed Authoring and Versioning) group Web document User 2 User 1 Need to handle: file locking authorisation Related to metadata

13 Content Negotiation Resources may be available in different formats: HTML, Word, Adobe PDF, … English, French, German Resources may use different features: Tables, Frames, Javascript,... User selection of appropriate resources is inelegant and prone to errors: Click here for HTML version, here for PDF Click here in your browser supports frames Transparent Content Negotiation addresses these issues

14 Transparent Content Negotiation Transparent Content Negotiation (TCN): In HTTP spec from start Not widely used Can be used to deploy new graphics formats: Variant list describes alternative formats: {"paper.html.en" 0.9 {type text/html} {language en}}, {"paper.html.fr" 0.7 {type text/html} {language fr}} ACCEPT image/png image/gif GET logo If client supports PNG and file.png exists, serve it else serve file.gif HTML document Request from client Server logic

15 Confused? DC, PICS, PICS/NG, XML, DSig, TCN, MCF. Are there too many metadata activities? I'm confident that things are coming together. In fact, I'm quite excited to see some of these issues finally approaching closure after the web community has struggled so long to address them. I hope things will become more clear to you and everybody else as things develop. Dan Connolly, W3C Architecture Domain Leader. Posted to www-html list on 28 May 1997 There is a need for these metadata activities Consider the metadata requirements for, say, a University prospectus

16 Metadata Architecture Metadata - the missing architectural component from the initial implementation of the web Addressing URL Data format HTML Transport HTTP Metadata PICS, TCN, MCF, DSig, DC,...

17 Conclusions Metadata is important! Various metadata protocols under development Dublin Core, PICS/NG and XML look important Clear need for communications between protocol developers (e.g. through W3C) Clear need for communications amongst online communities Need for careful planning in metadata management until protocols stabilize and mature tools are deployed

18 Further Information PICS: XML: SGML/Activity Web Collections: TR/NOTE-XMLsubmit.html DSig: DSig/Overview.html TCN: MCF: 0,4,11470,00.html WebDAV: authoring/