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Latest revision as of 19:08, 3 January 2009
XHTML-REST
The purpose of this presentation is to describe and justify a proposal for using microformants to constrain REST implementations.
Web Services: RPC vs. REST
- RPC: Remote Procedure Calls
- REST: Representational State Transfer
Advantages of REST over RPC/SOAP
- Much simpler to design
- Easy to identify appropriate nouns
- Don't need to define methods (verbs)
- Don't need a complete object model
- Easier to learn/invoke
- Always know what a URI means
- Need not 'tunnel' XML inside XML
Challenges of REST
- Discoverability
- No standard way to find services
- Interoperability
- Too many incompatible ways to encode links, data
- Extensability
- What if your schema isn't 100% right?
- Comprehensability
- What the heck does "state transfer" mean?
Solution, Part I-A: XHTML
- Use XHTML Basic instead of XML
- Don't need a rigid schema
- No namespaces; free to extend as needed
- Everyone (in this space) can write it
- Everything (in the world) can read it
Solution, Part I-B: XHTML Microformats
- microformats: Add 'semantic salt' to XHTML
- Annotate existing XHTML tags with meaning
- Machine-parseable yet human-readable
- Links as <a href=> and <form action=>
- Lists as XOXO: eXtensible Open XHTML Outlines
- ol, dl, ul
- Work like Mac OS X property lists
- CSS classes to reflect semantics
Solution, Part II: Browser clients
- Makes testing & documentation trivial
- The API is the documentation is the format
- Use subset of REST supported by browsers
- GET http://host/uri
- GET http://host/uri?query=string...
- POST http://host/uri?key=value...
- encode input data in urls, not XML docs
Solution, Part III-A: Web as database
- CRUD: Create, Retrieve, Update, Delete
- Structured URLs vs. Opaque URIs
- Note: need not reflect actual database
- Synthetic "user model" for public API purposes
- But, an easy way to start (cf. Ruby on Rails)
Solution, Part III-B: Web as database
- base: defines service
- GET base?query # search across all tables
- table: collection of URLs with same schema
- GET table?query # search across this table
- URIs become primary keys for joins!
- record: individual item, user, cart, etc.
- POST table?data # update record
Solution, Part III-C: Web as database
- Special conventions
- GET http://host/uri?view=edit # API as editable forms
- GET http://host/uri?view=api # API as dt/dd descriptions
- GET http://host/uri?view=list # key-value as dt/dd
- GET http://host/uri?view=table # key-value as th/td
- Other verbs become queries
- POST table?data # create a new record [vs. PUT]
- POST table?delete=yes # flag for remove [vs. DELETE]
The 0.8% Solution for Web Services
- (80% of benefit/20% of effort)^3
- XHTML vs. XML: 80/20
- GET/POST vs. REST: 80/20 x 80/20 = 64/4
- Database vs. freeform URIs: 80/20 x 64/4 = 51.2/0.8
- Half the benefit for 1% of the effort!
- Maybe not everything, but the basics easily
- Power comes from how much you can ignore
Implications
- The 'missing link' for REST?
- The 'killer app' for Ruby on Rails?
- The "tipping point" for web services?
- Looser than XML => easier compatibility
- Tighter than REST => better interoperability
- Simpler than SOAP => greater adoption
Examples (TBD)
- ?view=api (dictionary of valid requests)
- {base,table}?query (OpenSearch)
- base/ (home page)
- table/ (section page)
- table?view=edit (record creation forms)
Examples - Records (TBD)
- record/ (default view)
- record?view=edit (record update)
- record?view=list (dt/dd list)
- record?view=table (th/td row)
But Wait, There's More!
- Not just for web services
- Do your whole website this way!
- CSS classes + styles => prettified XHTML
- Don't Repeat Yourself (DRY): website == API
- Perfect solution for AJAX
For More Information
- Microformats http://microformats.org
- What are Microformats? http://tantek.com/presentations/2005/06/what-are-microformats/
- Discussion Lists http://microformats.org/discuss/
- XOXO: http://microformats.org/wiki/xoxo
- XHTML-REST
- research: http://microformats.org/wiki/rest-examples
- blog: http://www.opendarwin.org/~drernie/
- This presentation: http://microformats.org/wiki/rest-proposal-preso