Transcript WWW 7 Trip Report

New Standards
on the Web
Brian Kelly
UK Web Focus
UKOLN
University of Bath
1
Email Address
[email protected]
URL
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.
Contents
• Introduction
• Web Standards Overview
• Web Standards:
• Data Formats
• Transport
• Addressing
• Metadata
• Deployment Issues
2
Aims of Talk
• To give brief overview
of web architecture
• To describe
developments to web
standards (especially
those relevant to
library community)
• To briefly address
implementation models
Due to lack of time, talk will
not cover some new
standards, such as:
• Graphics
• Multimedia
• e-commerce
Standardisation
HTML
Proprietary
extensions
• De facto standards
PDF and Java? • Often initially appealing
(cf PowerPoint, PDF)
W3C
PNG
•
May
emerge
as
• Produces W3C
HTML
ISO
standards
Recommendations
• Produces ISO Z39.50
on Web protocols
Java?
Standards
• Managed approach to
• Can be slow moving
developments
and bureaucratic
• Protocols initially
• Produce robust
IETF
developed by
standards
W3C members
• Produces Internet
• Decisions made by
Drafts on Internet protocols
W3C, influenced by
• Bottom-up approach to developments
member and public
• Protocols developed by
HTTP
review
interested
individuals
PNG
URN
•
"Rough
consensus
and
working
HTML
whois++
code"
HTTP
3
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>
4
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
Problems
• Changes during CSS development
• Netscape & IE incompatibilities
• Continued use of browsers with
known bugs
5
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
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:
6
– Find all memos copied to John Smith
– How many unique tracks on Jackson Browne CDs
XML
XML Extensible Markup Language):
• A lightweight SGML designed for network use
• Addresses HTML's lack of evolvability
• Arbitrary elements can be defined (<STUDENTNUMBER>, <PART-NO>, etc)
• Agreement achieved quickly - XML 1.0 became
W3C Recommendation in Feb 1998
• Support from industry (SGML vendors, Microsoft,
etc.)
• HTML is being described in HTML - see <URL:
http://www.w3.org/TR/WD-html-in-xml/>
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XML Support
XML document with no
style sheet - XML tree displayed
XML support:
• Can be provided at backend
• (Partial) XML support in IE 5
• Also in Netscape 5?
XML document with style sheet
8
http://www.xml.com/1999/03/ie5/first-x.xml
XLink, XPointer and XSL
XLink will provide sophisticated
England
hyperlinking missing in HTML:
France
• 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
<commentary xml:link="extended" inline="false">
• Link databases
<locator href="smith2.1" role="Essay"/>
<locator href="jones1.4" role="Rebuttal"/>
XPointer will provide
<locator href="robin3.2" role="Comparison"/>
access to arbitrary
</commentary>
portions of XML resource
XSL stylesheet language will provide extensibility and
transformation facilities (e.g. create a table of contents)
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Addressing
URLs 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)
Solutions:
• Unique identifiers possible, but resolution difficult
• Solutions include DOIs, PURLs, etc.
• "URLs don’t' break - people break them". Think
about URL persistency and naming guidelines
10
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:




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Radical redesign using object-oriented technologies
Undergoing trials
Gradual transition (using proxies)
Integration of application (distributed searching?)
Metadata
Metadata - the missing architectural component
from the initial implementation
of the web
Addressing
URL
Metadata Needs:
12
•
•
•
•
•
•
Resource discovery
Content filtering
Authentication
Improved navigation
Multiple format support
Rights management
Transport Data format
HTTP
HTML
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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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:
–
–
–
–
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cataloging resources
electronic commerce
digital signatures
intellectual property rights
– resource discovery
– intelligent agents
– content rating
– privacy
• See <URL: http://www.w3.org/
Talks/1998/0417-WWW7-RDF>
RDF Model
RDF Data Model
RDF:
• Based on a formal
data model (direct
label graphs)
• Syntax for
interchange of data
• Schema model
page.html
Cost
Resource
Property
PropName
Cost
15
Value
Property
page.html
£0.05
PropObj
InstanceOf
PropertyType
Value
ValidUntil
23-Mar-99
Cost
£0.05
ValidUntil
23-Mar-99
Browser Support for RDF
Trusted
Mozilla (Netscape's
3rd
source code release) Party
provides support for Metadata
RDF.
Mozilla supports site
maps in RDF, as well
as bookmarks and
history lists
Embedded
See Netscape's or
Metadata
HotWired home page e.g.
sitemaps
for a link to the RDF
file.
Image from http://purl.oclc.org/net/eric/talks/www7/devday/
16
RDF Conclusion
 RDF is a general-purpose framework
 RDF provides structured, machineunderstandable 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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Deployment Issues
How can new technologies be deployed?
• Expect (hope) everyone will move to
new browsers
• Use technologies in backwardscompatible manner
• Develop additional protocols e.g.
– Transparent Content Negotiation
– CC/PP
• User-Agent Negotiation
• Use of proxy intermediaries
18
Deployment Issues
More sophisticated deployment techniques can be
adopted to overcome deficiencies in simple model
Original Model
HTML
resource
Web
server
browser
Sophisticated Model
HTML /
XML /
database
resource
Intelligent
Web
server
Intermediaries can provide
functionality not available at client:
• DOI support
• XML support / format conversion
19 • Authentication
Web server simply sends
file to client
File contains redundant
information (for old
browsers) plus client
interrogation support
Client
proxy
browser
Server
proxy
Example of an intermediary
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 may have a role to play in deploying
standards-based solutions
• Intelligent servers likely to be important
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