XOM API for Processing XML with Java

[Elliotte Harold <elharo AT metalab.unc.edu>]

Wolfgang Hoschek wrote:


> Any good ideas should be welcome. If one can figure out how to 
> effectively bound the cache and maintain high hit ratio it would be 
> interesting.

A synchronized HashSet would let us have O(1) insertion and lookup, but 
I'm not sure what the constant time performance would be like.

Bounding the set is tricky. We could just pick some number like 1024 for 
the set's upper bound, and clear it every time that value is reached. Or 
maybe allow it to be set by a system property, or some such.

The real question is whether the constant time retrieval from the set 
would be larger than just checking the names manually. Namespace URLs 
are expensive to check because:

1. They're quite long
2. The algorithm for checking them is quite involved, and creates lots 
of temporary strings.

Element names, in practice, are much shorter than namespace URIs and the 
algorithm for checking them is much simpler, and does not create any 
temporary objects. It just blasts through the string checking each 
character against a lookup table.

My gut feeling is that a cache would not be faster here, but I could be 
wrong about that.

--
Elliotte Rusty Harold  elharo AT metalab.unc.edu
XML in a Nutshell 3rd Edition Just Published!
http://www.cafeconleche.org/books/xian3/
http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim