NSPredicate

[Enrico Sersale]

I'm writing a Spotlight like search system. At the beginning I've started this 
project only as an experiment to see if a sqlite db could be efficiently used 
for an inverted text index, but, one by one, I've added other things and now 
I've a working system that can extract and store words and other attributes.
It is based on a sqlite db for storage and a tool, "gmds", that performs the 
queries and launches the extractor tasks.
At this point there are only two extractor bundles, plain text and jpeg, but 
there already are UTF8 stemmers for many languages.

All this stuff is already working; I've written a simple client that, for the moment, 
generates only simple queries for the text contents of type "foo AND bar"; it 
seems sufficiently fast.

I'm writing this mail because I don't want to use this thing as a new GWorkspace 
"feature"; I'm wondering if it would be better to use the gmds tools interfaced 
with the NSMetadataQuery class (something like NSDistributedNotificationCenter and gdnc).
I think that I could also write NSMetadataQuery, NSMetadataItem, 
NSMetadataQueryAttributeValueTuple and NSMetadataQueryResultGroup; this doesn't 
seem a very difficult task.
But NSMetadataQuery needs NSPredicate and I think that I can't write it.

So, the question is: is somebody working at NSPredicate (and at the other 
NSMetadata* classes)?