Web Architecture

Addressing and Data Formats

Dan Connolly
W3C

WAPForum Meeting
February 1998
Fort Worth, TX

Overview

• Architecture
• Addressing: URIs
• Data Formats: XML
• Q&A...

Web Architecture

1. Addressing: URIs
2. Protocols: HTTP, ...
3. Data Formats: HTML, XML, ...

notes from '91

Addressing: URIs

• Jun '94: URI spec Informational
  (RFC 1630)
• Dec '94: URL Proposed Standard
  (RFC 1738, 1808)
• Aug '98: Common Syntax to Draft Standard
  (RFC 2396)

Addressing: Issues

• Parsing, extensibility bugs
• Maintenance of the list of URI schemes
  guidelines
• Persistence (URNs, DOIs, rights management)
• Integrating TV, telephone

Addressing: Opportunities

1st class objects vs.

• overuse of POST
• MIME x-types
• mailto: misnomer

"value of the network varies with the square of the number of resources"

Data Formats

• HTML, plain text
• GIF, JPEG, ...
• Style Sheets: CSS, XSL
• XML

Format Negotiation

• In Theory: Client advertises capabilities
  Server optimizes response
• In Practice: Client advertises product codes
  Server kludges around bugs

Format Negotiation

• Lesson: evolution of capability list

W3C Data Format Architecture: XML

• Self-evident, self-similar structure
  no tag inference
• Make HTML components usable by reference

XML: past, present, future

• Fall 1996: 1st Draft at SGML Conference
• Nov 1997: Proposed Recommendation
• Feb 1998: Recommendation
• June 1998: Continuing Work on XML
• Jan 1999: Namespaces Recommendation

XML Applications

• HTML Math (MathML)
• Synchronized Multimedia Integration Language (SMIL)
• Resource Description Framework (RDF)
• Scalable Vector Graphics (SVG)

XML Namespaces

• Address tag name collisions, ambiguity
• Namespaces are 1st class (addressable) resources

RDF

metadata infrastructure for...

• Automated contract exchange
• Web structure analysis
• Bibliographic records (Dublin Core)
  • Persistence (availability guarantees, rights management)

XML Activity

1. XML Schema WG
2. XML Linking WG
3. XML Fragments WG
4. XML Syntax WG
5. XML Infoset WG

XML Schemas

• Provide DTD facilities in self-similar syntax
• Provide 1st-class module facility
• Integrate with modern data stores?
• Integrate with modern software development?

XML Linking

• modularize HTML linking
• link services, annotations, ...
• bring the web into the '70s

XML Fragments

• deal with fragments out of context
• update-grams?
• packaging?

XML Syntax

• profile
• maintenance

XML Infoset

• make the implicit data model explicit