When designing an XML feed for structured data, what is good practice, and what anti-patterns are there?
I’d like answers that cover XML structure and content, and/or transport mechanisms.
Transport Mechanisms
With current technologies is FTP/SFTP a good technology? Are there cases where it is the best fit as a solution?
Generally I prefer HTTP pull feeds, but what weaknesses does using HTTP have?
What other feed mechanisms should be considered with their pros and cons?
XML Structure Content
When there is no suitable existing DTD/schema that exists, what practices can be followed to come up with a good XML design?
Two anti-patterns for this I have already given in my answer below.
But what should I be doing when designing a feed? I’d like to hear about tags vs attributes, how relational data (esp. many-to-many relationships) should be conveyed in XML, etc.
Note: I have completely rewritten the question, as even with the bounty offered it wasn’t getting a lot of love. (The old version is in the edit history if you want to see it. This version should be pertinent to the answers already given)
A good feed has
1) A schema, because that way you can check it programatically and you know when it’s been changed – saves lots of arguements
2) Tells you when it’s down
3) Works consistently
4) Will handle stops, starts, pause, rewind gracefully
5) Has a test service that fully exercises all the existing feed features
6) Has a new features service for sand box development
Realistically I’ve only worked with feeds that deliver 1 and sometimes 2, but we can dream.