The idea here (lumberjack and CEE) is to support and encourage the applications (including the kernel) to create structured logs so that the data that you are referring to as the 'data' section is easier (and thus more reliable) to deal with.
the first step is to have the normal message just stuck in the 'data' section, and the lumberlog library ( http://algernon.github.com/libumberlog/umberlog.html ) is designed to do just that. It can be LD_PRELOADed for any application and it modifies the syslog() call to log a structured log (JSON structure with added metadata). It then allows the application programmer to change syslog() calls to ul_syslog() calls and add additional name-value pairs.
the next step is to create a more complete logging API that allows the application programmer to more easily create structured logs. Debate over how that could/should work is ongoing.