[sword-devel] [Wiki Frontend comparison] Proximity searches

[DM Smith]

On Feb 28, 2009, at 8:30 PM, Matthew Talbert wrote:

>>
>> Bible Desktop/JSword (thus AlKitab and FireBible) have proximity  
>> searches
>> across verse boundaries. The syntax is reminiscent of Lucene, but a  
>> bit
>> different.
>> Aaron ~3 Moses will find all verses with Aaron within 3 verses of  
>> Moses.
>
> If I may ask, how do you implement this with lucene? Is it totally
> separate from the indexed search?


We build it on top of Lucene.

In JSword, search result (and partial search results) are expressed as  
bitmaps, with Gen 1:1 being bit 1 and Gen 1:2, being bit 2 and so  
forth. (actually, we have several representations, but this is  
conceptually the easiest to understand).

If the term ~n (where n is a number is present), the request is split  
into two parts (before and after). These are searched separately.

We "blur" a second bitmap (the one with Moses) by 3 so that bits  
within 3 of the current bits are added in. Then we take the  
intersection of the two.

I've left out a couple of details, but you can see all the details in  
org.crosswire.jsword.index.query.BlurQuery and the routines it calls.

Another feature JSword layers on Lucene is range restriction.
A search preceded by [passage range list] will return verses in that  
range. If it is preceded by -[range] it will return verses that are  
not in that range.
The passage range list can be anything that JSword understands as a  
list of passage ranges, such as Gen-Ex, Matt 5, Rev 2:3.

This simply builds a bitmap for the range and intersects it with the  
result of the search following the range.


In Christ,
	DM