[UPDATE: the old scan image of the luggage strip got lost. The image on the left is another strip, which makes the same point.. it is a flight from Singapore to Seattle, via Tokyo. I won;t change the text below, ’cause it was specific to PDC2003… but substitute LA with Singapore, Atlanta with Tokyo, Milan with Seattle and you’ll get the point 🙂 ]
Surprised once again by the incredible luck of being able to find my case actually arriving with me after 3 planes hops (despites of the horror stories I often hear: person in one emisphere, luggage in the other and so on), I stood in contemplation of that white sticky paper band that I usually ignore, leaving on the case until the next flight and I found it a very good real-world metaphor of WS-Addressing (though that would have fitted even better in the old WS-Routing). It’s not that I didn’t know its purpose since than: simply, I didn’t make the connection with the WS world.
That small piece of paper makes the magic possible: the big ultimate destination, Florence, has its own unique “qname” (FLR: incidentally it corresponds to one token of that mysterious SQL-like language that travel agencies girls are so fluent with) and it’s what really counts to make the luggage reach (eventually) the destination. Other info (like intermediaries qnames and flight number/time hints) are extremely useful to make the user (me!) experience smooth, making the case follow the owner in every hop (notice that those intermediary references share the same format of the ultimate receiver: airport id, flight and departure time): but at the end of the day, in line of principle they could be simply ignored and the route dynamically established in real time (workable in a distributed system, but God forbid in case shipping…).
The body element is, of course, all my laundry. And to push the analogy a little further, there was another header-like element attached to my case: a small orange strip of paper saying “Security: checked” or something similar. That means that the guy in L.A. didn’t trust me (or, with less paranoia, I was the lucky winner of a random inspection: the case was not completely full because I’ve foreseen the possibility, so there weren’t pityful scenes to close it back) but the guys in Atlanta or Milan did, or rather they trusted their L.A. colleague who attached to the case the token. I’ll let you guess at what WS-specification I’m referring now… 😉