Protocols are hard: Cowpaths accommodated
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This document discusses the challenges of creating protocols and ensuring they are self-describing so users understand how to use them. It notes that protocols need to accommodate unexpected uses or "cowpaths" to be sufficiently flexible. Examples of photos are provided to illustrate the points about protocols.
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Protocols are hard: Cowpaths accommodated
Editor's Notes
- Protocols are hard, because distributed systems are hard, and interoperability is hard.
- Part of my day job is fielding questions for developers who have trouble with HTTP.
- Questions like "why isn't my page caching?" "why isn't gzip working?" "what does this mean?"
- Many issues can be found by inspecting responses, and observing how a resource behaves.
- RED is the Resource Expert Droid -- an automated tool for testing HTTP resources, whether they're Web pages or RESTful Web Services.
- [ screenshot showing interface for a basic response]
- [ screenshot showing interface calculating cacheability of response ] 
- [ screenshot showing interface validating resource ]
- [ screenshot showing interface verifying proper operation of partial response ]
- [ screenshot showing interface verifying gzip content negotiation ]
- RED can find common errors like a Content-Length that's incorrect or a header with incorrect syntax.
- And it also catches issues like headers that are too big, URIs that are too long, and URIs that contain illegal characters.
- You can drill down on any problem and get a complete explanation of the issue and its impact.
- RED can also tie-in to other tools: HTML / Atom / RSS / CSS validation. In time, it will have more knowledge of common payload formats.
- I have a hidden agenda with this tool -- encouraging RESTful design.
- If your message is self describing (E.g., Allow header, Link header), RED can navigate them and give you a richer experience.
- OTOH, if you use non-standard headers or your messages aren't self-describing, it won't work as well with RED.
- RED can, in time, support extension protocols like OAuth, OpenID, AtomPub and others. 
- Under the covers, RED is asynchronous, event-driven Python, from sockets up. GPL License.
- See [URL] to use, download or contribute. Work is still in progress.