Lookup tables or equivalent

[David Carlisle]

> The solutions we've seen have all more than likely been linear searches 
> (an implementation could do better but I think it's unlikely)

That was one reason I sugested switching to elements rather than string
sequences as (perhaps) it is more likely that they get indexed (in xslt
you could force indexing with xsl:key) but I didn't mention that as it's
not clear which processeors would index what, especially if the actual
data only has length 12.

David