Transcript Powerpoint 97 format

The Latest Web
Developments
Brian Kelly, UK Web Focus
UKOLN
University of Bath
Bath, BA2 7AY
http://www.ukoln.ac.uk/
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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
Data Formats
• HML 4.0
• Dynamic HTML
• CSS 2.0
• XML
Transport
• HTTP/1.0
• HTTP/1.1
• HTTP/NG
• URNs
• DOIs
• Dublin Core
• RDF
Addressing
• URLs
Metadata
• PICS
Implications
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Web Protocols
The web was originally
based on 3 protocols:
• Data Format
(user interface):
HTML
• Transport:
HTTP
• Addressing:
URLs
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Data
format Transport
Addressing
HTML
HTML:
•
•
•
•
Defines structure
SGML application
Platform and application independent
Simple and therefore easy to create
but:
• Netscape / Microsoft browser wars began
• HTML extensions appeared
• (Proprietary) scripting languages add new
functionality and also complexity
• Universal access begins to be lost
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HTML Develops
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During 1997 recognition of dangers of HTML
wars
Netscape and Microsoft began working with
W3C on development of new protocols
HTML 4.0
• W3C recommendation
• Primarily defines structure
• Layout tags for backwards compatibility
CSS 2.0
• W3C draft
• Used to define appearance
CSS 1
CSS level 1:
• W3C recommendation in December 1996
• Partly supported in IE 3.0
• Early designs attempts confirmed power of CSS
but highlighted backwards compatibility issues
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CSS 2
CSS level 2:
• Provides richer functionality
• Addressed backwards compatibility issues
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http://www1.shore.net/~straub/
wprmultb.htm
Making HTML Dynamic
DOM:
• Document Object Model
• W3C activity
• Enables client-side scripting languages to
manipulate HTML and CSS elements and
their content
• Sometimes referred to as dynamic HTML
But:
• Netscape's implementation is nonstandard
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DHTML Example - 1
Making documents "collapsible" is very easy:
on mouseclick in heading
set visibility and display of body off
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DHTML Example - 2
Dynamic HTML can be used to develop improved
user interfaces.
In this example an expanded menu is provided.
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DHTML Example - 3
DHTML can be used to provide interactive
systems - e.g. for CBL, simulation
In this example the
pieces can be moved.
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Compatibility Issues
Compatibility with old browsers / other
browsers can be provided by:
• Using safe, backwards
compatible features
• Checking for browser
type by client-side
scripting language
• Checking for browser
type by server
Alternatively ignore backwards compatibility
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The End for HTML?
HTML 4.0 and CSS 2.0 provide a rich
environment for describing document structure
and appearance
But:
• Standardisation of new elements is slow
• Supporting communities with specific needs
(e.g. Maths) will result in large, complex HTML
• Applications have specific needs (e.g.
<STUDENT-NUMBER>
• HTML 5, 6, … does not appear to resolve
these issues
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XML
XML:
• Extensible Markup Language
• Can be regarded as a lightweight SGML
• Supported by SGML community
• Some support in Internet Explorer 4.0
• Netscape promising support in future
• XML 1.0 became a W3C recommendation
in Feb 1998
• See <URL:http://www.w3.org/XML/>
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XML Applications
MML / CML
Scientific communities have defined Math and
Chemical Markup Languages
CDF
Channel Definition Format provides a proposed
standard for push technologies
RDF
Resource Description Framework provides a
proposed standard for a metadata architecture
...
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CDF Example
NewsAgent:
• an eLib project
• evaluating potential
for CDF for pushing
information
Software to create CDF
becoming available e.g. FrontPage 98
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http://newsagent.ukoln.ac.uk/channel/
<CHANNEL HREF="http://newsagent.ukoln.ac.uk/channel/top.cdf">
<LASTMOD="1998-03-05T00:39" />
<SCHEDULE>
<INTERVALTIME DAY="1"/>
</SCHEDULE >
<ITEM HREF="http://newsagent.ukoln.ac.uk/channel/Events.html">
<TITLE>Events</TITLE>
Typical CDF File
</ITEM>
Transport
HTTP 1.0
 Widely used
 Inefficient
 Cache unfriendly
HTTP/1.1
 Addresses deficiencies in HTTP/1.0
 Cache-aware
 Available now (e.g. latest version of
Apache)
 Browser support?
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Transport
HTTP/1.1
• Evolutionary development
HTTP/NG
• The Next Generation
• Based on distributed object-oriented model
Issues:
• Browser support
• Server support
Note:
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About 40% of UK University central
websites servers support HTTP/1.1
Addressing
URLs:
• Provide addressing for the web
• Consider http://www.dec.com/internet/
applications/
• Problems:
– Company reorganises website
– Individual leaves
– Company is taken over!
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Solutions (1)
URNs:
Uniform Resource Names: make identification of
Internet documents possible.
URN identifiers are persistent and unique.
See <URL: http://www.ietf.org/
html.charters/urn-charter.html>
PURLs:
Persistent URLs: Point to a resolution services
rather than the resource itself.
See <URL: http://purl.oclc.org/>
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Solutions (2)
DOIs:
DOIs use CNRI's Handles
• Document Object Identifiers
• Costs $1,000 to register
http://hdl.handle.net/10.1016/
S1384107697000225
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hdl://cnri.dlib/august95-contents
Addressing: Conclusions
Conclusions:
• No clear technological winner
• Performance issues
• Is it just for "publishers"
• Business model uncertain
• Deployment and "real world citation"
issues
• Still need for information providers to
give careful thought to URL naming
schemes
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Metadata
Metadata:
• The missing architectural component of the Web
• Many developments in progress:
– PICS: "this resource contains bad language
rated as X"
– Dublin Core: the author's name is xxx and his
email address is yyy
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– Web Collections: these set of resources are
related and should be download together /
printed as a single document / …
– Distributed Authoring: the following can
update this document
– ...
RDF
Resource Description Framework (RDF):
• Too many ways of handling metadata
<META NAME="DC.creator"
CONTENT="(TYPE=name) UKOLN">
<META NAME="DC.creator.name" CONTENT="UKOLN">
...
<?xml:namespace
name="http://purl.org/metadata/
dublin_core#" as="DC"?>
• RDF provides
generic
<RDF:RDF>
<RDF:Description
infrastructure for
RDF:HREF="http://www.bar.com/some.doc"
metadata
RDF:BAGID="Statement_001">
<DC:Creator>John Smith</DC:Creator>
</RDF:Description>
• Based on XML
<RDF:Description
RDF:HREF="#Statement_001">
• See <URL:http://www. <DS:CreatedOn>1998-0206T14:00Z</DS:CreatedOn>
w3.org/PICS/>
<DS:CreatedBy>Jane
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Cooper</DS:CreatedBy>
</RDF:Description>
</RDF:RDF>
Web Architecture
Web architecture is:
• Growing in
complexity
• Maturing,
becoming
more robust
Must understand
architecture to
avoid:
• Escalating costs
• Degradation of
service quality /
functionality
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Data Transport
format
Address- Metadata
ing
Information Landscapes
Developments such as Web Collections will
enable metadata for groups of related
resources to be defined for:
• Providing enhanced user navigation
• Facilitating printing, off-line browsing,
...
• Facilitating indexing
• etc.
The term Information Landscapes has been
coined to refer to changing, configurable
views of networked resources
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Information Landscapes
Landscapes can be developed by / for:
• Institutions
• Service providers
• Groups (e.g. undergrads)
• ...
Information Landscapes can be used for
delivering information based on:
• Institutional needs and interests
• End user's technologies / interface preferences
Implications:
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• Ownership, legal and copyright issues
• Change control
• Visibility
• Maintenance
What demand is there?
Using The Technologies
How / when are new technologies to be
deployed?
• Use "safe" features to ensure backwards
compatibility
• Check for browser functionality at server
• Check for browser functionality at client
• Deploy on Intranet for access to internal
resources / external resources
• Use tools which can regenerate systems
when standards change / develop
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WebWatch
Nos. of hyperlinks
Project based at
UKOLN to monitor web
developments in UK
Analysed various
communities:
• University entry points
• eLib projects
• Public libraries
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Server software
File size (HTML)
Conclusions
To conclude:
• Underlying web protocols continue to
develop
• An understanding of development of
the web architectures is needed to:
– Exploit appropriate new developments
– Avoid going in wrong direction
• Automated tools are essential
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