The Airline Ticket Consolidators and Bucket Shops FAQ is fun reading if you're ever wondering about how airline fares work, specifically for flights between the US and the rest of the world. Edward Hasbrouck knows his stuff, though he's got some errors regarding the CRS companies (for instance, even at the time of the last update, Galileo was not majority owned by airlines).

This brings me to my main point of this post (took me long enough!).  I've said in the past to be extensible with your service interfaces, but to draw the line in the sand with your schema.  Use it to your advantage!  Use the great features of XML-Schema (like parameter value ranges, optional elements, substitution, etc.) which aren't readily available when defining interfaces in other ways.  And as long as you have the CPU cycles to spare, validate the requests against the schema.[Greg Reinacker's Weblog]

We've gone round and round about this at work.  Our problem is that some of our services have huge schemas and validation is just too expensive.  The solution the developers took is to validate, but not using schemas.  The problem now is that your validation is disconnected from your schema.

I work with an individual who habitually sends subjectless emails. This used to not bother me much, but now with my inbox filling with blank subjects, I decided to write an Outlook rule to autorespond with something like "I won't read this unless you put a subject on it". No such luck, Outlook will key off a particular word in a subject, but has no way to select messages without a subject. Foiled again!