At work yesterday we discussed how backwards compatibility over time leads to so many layers that there might actually be careers for programmer archaeologists.
Our conversation started with our organization's move towards IPv6 (start early, learn early, act as a consultant for those who waited, and profit!) and got into the details of a life of a packet for a person using IPv4 to access a resource we might host over IPv6 only. Someone pointed out how a 6to4 outbound relay server would help us as recommended by Geoff Huston.
We then tried to imagine the same transaction occurring for a web app where javascript requests XML (you do this every time you click a message in gmail) and just how much has to happen. The XML was generated on the server side by a script, which ran on top of a JVM (running on top of Xen or KVM (which was live migrating via a CLVM-based cluster)) which queried a database, which was using the ext3 file system, which retrieved blocks through a fibre switch to get it from a SAN, which distributed the data over 120 SATA disks using RAID-X.... all the way back and up down through OSI but cranked back through a 6to4 Relay Service and finally applied to the DOM in a browser with more lines of code than a Unix kernel (a relic left over from the browser wars for backward compatibility with invalid HTML)... and we had to laugh... Glad I learned to deal with abstraction early.
Someone mentioned the book A Deepness in the Sky to bring up the concept of a programmer archaeologists which I found rather funny. As per the wikipedia:
"An interesting feature of the Qeng Ho's computer and timekeeping systems is the advent of "programmer archaeologists"[1]: the Qeng Ho are packrats of computer programs and systems, retaining them over millennia, even as far back to the era of Unix programs (as implied by one passage mentioning that the fundamental time-keeping system is the Unix epoch, retained for backwards compatibility). This massive accumulation of data implies that almost any useful program one could want already exists in the Qeng Ho fleet library, hence the need for computer archaeologists to dig up needed programs, work around their peculiarities and bugs, and assemble them into useful constructs."
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