[jsword-devel] Extending Lucene Indexes and stemming in particular

Fri Apr 18 01:23:26 MST 2014

On 18 April 2014 01:40, DM Smith <dmsmith at crosswire.org> wrote:

>
> On Apr 17, 2014, at 12:09 PM, Chris Burrell <chris at burrell.me.uk> wrote:
>
> Hello
>
> STEP uses stemming to improve search results, in some queries (whether on
> Sword modules or otherwise).
>
>
> Stemming is very useful. On occasion, there is a need for a non-stemmed
> search. Especially for theological purposes. But for general purpose
> searching it should be the default.
>
> Are you suggesting we have 'heading' being the stemmed search and
fullHeading (or something like that) being the non-stemmed? I do think that
by default however, we should have the normal search. We experimented with
stemming in STEP by default and it can be quite confusing to look for a
particular word and hit others. Stemming doesn't always work the way you
expect.

> I've some times thought it'd be good to double index: stemmed and full
> word.
>
> Double indexing is a need if you want both. The stem for genealogy
resolves to genealogi (because of the plurals) which is why my search
wasn't hit. We can't use the same field.

>
> There are currently 2 limitations in JSword, both of which could easily be
> fixed. Please let me know if you have concerns around me implementing both.
>
> a- the frontend can't extend/control the use of indexes. I'm suggesting we
> add a registerFieldIndexer(fieldIndexer) with a simple interface:
> indexField(doc, osis). This would allow frontends to specify its own
> indexing. This would allow a frontend to index new things, or enable term
> vectors / store fields, etc.
>
>
> I'd really rather that we didn't go down this route. I don't mind plugin
> architecture as a way to experiment with different techniques, but I'd
> really rather that we all benefit from the changes.
>
> Fine.

>
> b- Extend the LuceneIndex to have a stemmed version of the heading. We
> could replace the existing index, but that would mean all frontends will
> require re-indexing.
>
>
> I think the same manner that we index the main verse text should be
> applied to all text: intro, heading and verse text.
>
> Happy to do the change for all three.

>
> c- Had JSword been configured to 'STORE' the content of some fields, I
> would have used that for headings. For example, if the headings is stored
> in the index, STEP would not need to do an osis extract and XML transform
> to display to the user. It could come straight from the index. Two
> possibilities here: change the existing index field configuration, or
> duplicate into a different field.
>
>
> I think we should make store an option, possibly the standard.
>
What I don't want to happen is end up in a situation where the Index is
shared in different configurations by different apps. That would break the
frontend. Even if you can ask, 'do you support', that's unnecessary
complexity, that means that a user will have to re-index each book he has
to support different front-ends. It also means that if a frontend forgets
to ask whether some fields are indexed in a particular way, then he's going
to have broken functionality in the frontend due to another frontend
overriding the defaults. At this stage, I'd rather have app-specific
indices.

>
> Right now the way we do the index prevents us from using Lucene to
> highlight the search hit. If that is STORE, then I'd be in favor of making
> STORE standard. I wonder if our stripping the text to no include OSIS
> before indexing will frustrate this change.
>
> Store is a requirement for highlighting (
http://lucene.472066.n3.nabble.com/Highlighting-for-non-stored-fields-td1773015.htmland
http://wiki.apache.org/lucene-java/LuceneFAQ).

It still should be an option for the sake of devices that are disk limited.
>
> d- the other side of c- is that ideally multiple headings should be stored
> in multiple entries to the same field, rather than a concatenation of the
> field (doesn't much matter if it's only ANALYZED)
>
>
> Some verses have headings in the middle of the verse. Don't make the
> mistake of assuming an order of heading. Or that heading contains only
> pre-verse material or all pre-verse material.
>
> I'm not making that mistake... All I'm saying is that headings should be
stored in different entries in the same field.
doc.add(fieldName, heading1);
doc.add(fieldName, heading2);
doc.add(fieldName, heading3);

This means that you could retrieve one of the headings you want, rather
than all. i.e. Psalm 3.1 Non-canon-heading Canon-heading could have 3
separate fields.

>
> *I only need one of a- or b- to be able to progress. Happy to do either. I
> don't need c- because I've worked around, but it would have been nice to
> have some control over that. *
>
> pros & cons:
> a- more extensible in the future, other frontends don't benefit from
> enhancements
> b- solves an immediate problem, but impacts all frontends (i.e. space used
> in index).
>
> The only other bit in my mind is whether we need to ensure
> index-cross-application compatibility. I suspect some of this will tie in
> with the good work that Sijo has done on index management.
>
>
> The index management will be more critical with such a change. I've talked
> about having a manifest which defines the characteristics of the index. If
> we share an index created by two different systems, it will be important to
> "know" what an index supports.
>
> as described above, I'd like to avoid this. I don't think a frontend
should have to worry about other frontends 'corrupting' the index (i.e.
redefining fields, changing the store status, etc.). I'd rather my own
index at that point.

> One of the changes that is being worked on is the update to a more recent
> version of Lucene. This affects how stemming is done. The way we are doing
> it now is deprecated and dropped.
>
>
> Let me know what your preferences are.
>
>
> Progress not perfection. Shared, configurable changes.
>
> Chris
>
> _______________________________________________
> jsword-devel mailing list
> jsword-devel at crosswire.org
> http://www.crosswire.org/mailman/listinfo/jsword-devel
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.crosswire.org/pipermail/jsword-devel/attachments/20140418/2ea1724d/attachment.html>