Developing Web Architecture

Overview

20 minutes

• Architecture issues and topics: top down, bottom up
• Background: Principles, Axioms
• Dos and Don'ts

discuss: how do folks learn Web Architecture? how will the TAG disseminate its results?

Issues List

13 issues so far, including:

• w3cMediaType-1 : Should W3C WGs define their own media types?

  pretty easy: yes...

• customMediaType-2 : What commonality should there be among W3C media types?

  not too messy...

• nsMediaType-3 : Relationship between media types and namespaces?

  we're likely to chew on this one for a while.

Outline: Categories of Issues

The Web is a medium for people and machines to communicate using shared space...

1. What does a URI identify?

   what does it not say?

2. How do we convey information?

   (languages, documents, ...)

3. Representational State Transfer (REST)

   identity, state, and GET

4. What does a message mean?

   message passing and share state

for details: architectural categorization.

Context

The TAG is not starting from scratch...

• Existing specs (RFCs, RECs)
• Engineering Principles
• Web design notes

Principles: motherhood & software engineering

• "Keep it simple, stupid"
• Modularity

discuss: what balances the tendencies of large design groups in the W3C process?

discuss: coordination costs of modular work?

Principles: Internet Scale

• Constant change
• Tolerance: "be conservative in what you produce, and liberal in what you consume"
• Decentralization

further reading: RFC1958, Carpenter, 1996

discuss: the costs of tolerance

Principles: Web Design

• Test of Independent Invention
• Principle of Least Power

  declarative markup

• Downhill steps
• Fractal Design

further reading: Design Principles, TimBL, 1998

Section 3: REST: Identity, State and GET

some rules well-documented, some not so:

• Users cannot be held accountable for GET effects

  in HTTP 1.1

• Anything which does not have side-effects must use GET

  else N>1 Webs

Do: use GET to wander around the space

• to query a database
• to read a file
• to ask a question

large scale result: search services like google

Don't: hold users accountable for GET

"If you agree, follow this link..."

• what about cache accelerators?

• links can come from anywhere, not just the page with the license terms

Use PUT/POST to leave your mark.

further reading: from Documents to Deeds in UI Desing Issues, section 9.1.1 Safe Methods in HTTP 1.1