There aren't many compatibility issues at the moment and preserving the
name as the interface would be better compatibility anyway. IMO The
interface name is more important then implementation name so I think
that it gets priority.
1/ shall we make the interface PrefixMap, and call current PrefixFix
PrefixFixStd, and have a factory?
Other future implementations include one for XML-valid prefixing for
example as Turtle and XML are diverging.
The cost of finding a perfect Turtle one vs fast may become significant
as well. There are escapes in the local par tof a prefix name in
Turtle-1.1.
The abbrevKey used in FastPrefixMap is the URI upto the last '#' or
failing that '/'.
This is a prefix look up only when two prefix URI abbrevKeys share a prefix.
This is rare (I claim!). I added some tests to
AbstractTestLightweightPrefixMap to investigate ...
and the two implementations differ here. The FastPrefixMap does not
abbreviate where the old code does.
2/ In the general purpose PrefixMapStd class, we could keep a Map from
registered URI string to prefix to speed up that common case.
A Map is smaller than the Trie (which has a map at each level, so
http:// is 7 maps). It does not optimize cases where one prefix
possibility is a prefix of another, and it falls back to brute force
here. Does this case matter? (Using the abbrevKey and stripping back
the possibilities would be a possibility.)
This all gets a lot more complicated for RDF 1.1 where the local part
can have escaped / and # in it.
Over-engineering 1:
Delay the Tries creation until the first call of abbrev or at the end of
parsing (the case of many small files concatenated might have had a lot
of prefixes)
Or build the Trie during output only? if there is an abbrevKey, find
the abbreviate old style, and install it. This is using in a cache fashion.
Otherwise the suggestion of OutputPrefixMap looks good.
Over-engineering 2:
I thought a bit about two interfaces - one for parsers, one for writers
but it seem to be quite complicated for little or no value. What's more
a prefix map may start by being used for parsing and then used for
writing (if and when old PrefixMapping gets sorted which would be good
at Jena3 - it's XML centric).
I'm happy to put time in to help with changes.
Andy
