Logic Bag concerns

I hate to lob this into the discussion so shortly before IETF, and
particularly when I haven't had time yet to finish looking at HTTP/1.1,
but....

I'm troubled by Logic Bags (3.11), which apparently have been added to
support the Unless header and byte ranges.  My particular concern is
how to implement the relational operators, such as "gt".  It seems to
me that their implementation is header-dependent.  "gt" for
Last-Modified is different from "gt" for Content-Length and from "gt"
for "Content-Version".  Now, it's easy to state, on a case by case
basis, what the correct behavior should be.  But what should a server
do in the face of unfamiliar headers?  Example:

I get header Foobar: 100.  My bag says {gt {Foobar "AX"}}.  How do I
compare them?  Lexicographically?  Numerically?  (What base?)

Dave Kristol