[jsword-devel] Lucene index help

[Martin Denham]

Hi,

It took a while to digest all that.  I hadn't really used Lucene very much
until a few months a go so it is still new to me.

*Bless/Blessed Issue*
The version of BibleDesktop I was using to generate indexes was 1.6 so I
presume that BibleDesktop version 1.6 did not include stemming.  I ran
bridge.BookIndexer on my pc to recreate the ESV indexes and copied them down
to my Android mobile and the bless/blessed test now passes and blessed
returns lots of results.  I am not sure which other tests I should run with
different language modules.  I tried 'god love world' but Jn 3:16 was not
returned but 'God loved world' obviously did return Jn 3:16.  Is that
correct?

*Build of of JSword for Android*
I have not been very thorough in versioning JSword for And Bible builds but
have just done whatever necessary to get And Bible to work.  I took a copy
of jsword from svn a few months ago (I need to refresh it) and that is what
I have been including with And Bible, with a few small changes.  However
Android specify that you have to use JDK 5 or 6 so I built jsword and common
using jdk 6.  Unfortunately some of the jars required by jsword are built
with jdk 1.4 and cause various warnings to be produced but work okay apart
from that.  If there is any move to update jsword to jdk 5 or 6 then Android
developers would support it.  Also updating the jars which were built with
jdk 1.4 to later versions would be great.  However, I have not seen any
errors caused by the current versions so can see no rush to upgrade
versions.

*Index Repository*
I see there are many issues around the compatibility of any pre-built
indexes for remote download but creating indexes on mobile phones has been
an issue and has caused a fair amount of adverse comments so it will make a
lot of people happy if an index download repository is provided.  Initially
I believe it would only be And Bible that would use the repository and the
users seem a fairly forgiving set of people on the whole.  We could start by
putting indexes into a folder with a v1 in the url and also have a time of
testing before general release.  Are you thinking of a more extensive index
repository structure?  I wonder if in the future a method could be added to
JSword that attempted to check the compatibility of the installed index and
allow the ui to warn the user if it had become incompatible due to a
software upgrade.

Thanks for all your efforts on JSword.  It is a great library.  I am getting
to know it a bit better month by month.

Best regards
Martin

On 4 November 2010 19:20, DM Smith <dmsmith at crosswire.org> wrote:

>  I thought I'd outline the variables that go into building an index that
> can be reliably searched.
>
> The unit of an index is called a Document. In our case, this is a verse, a
> dictionary entry, ..., anything that SWORD identifies as a keyed piece of
> information.
>
> A document consists of one or more fields having content. We have several:
> content, note, strong, ..., with content being the default. One specifies a
> field search as with:
>     strong:H3068
> If no field is specified, the default is searched.
>
> It is possible to have fields that are not searchable but merely store
> information. We do this with the key for the item. That way, we know what we
> have gotten back from a search.
>
> Each field is built independently from the others. Each has its own
> analyzer. Though two fields might have the same, it is best to ignore that.
> An analyzer consists of a tokenizer which splits up text into a stream of
> tokens and filters applied to that stream.
>
> Generally we think of tokens as words, but it is a bit more complicated
> than that. The StandardAnalyzer also tries to identify phone numbers,
> acronyms, URLs, and other common English constructs. It also uses white
> space as word delimiters and punctuation as a hint to word boundaries. SWORD
> uses the StandardAnalyzer, but JSword does not. It uses a variation of the
> SimpleAnalyzer, which uses white space and punctuation as boundaries.
>
> One of the complexities is that not all languages use the same rules for
> word boundaries. E.g. Chinese uses one glyph per word and spaces are not
> used to separate words. Thai does not use white space and it looks as if all
> the letters are run together. Ancient Greek also ran words together
> consisting of all capital letters. These need to be treated specially. The
> typical approach with Chinese, is to do bi-gram searching. That is, if
> looking for a single glyph, look for just that, but if looking for multiple
> glyphs, break it up into pairs and look for those pairs. For Thai, the
> typical approach is to use a dictionary and Unicode tables to break up the
> string of characters into words.
>
> Regarding Unicode, it has progressed over the years with several versions
> being released. And each version of Java implements a version of Unicode.
> Quoting the JLS: (
> http://java.sun.com/docs/books/jls/third_edition/html/lexical.html)
>
> Versions of the Java programming language prior to 1.1 used Unicode version
> 1.1.5. Upgrades to newer versions of the Unicode Standard occurred in JDK
> 1.1 (to Unicode 2.0), JDK 1.1.7 (to Unicode 2.1), J2SE 1.4 (to Unicode 3.0),
> and J2SE 5.0 (to Unicode 4.0).
>
> From what I understand Java 6 is also Unicode 4.0 and Java 7 is planned to
> be Unicode 5.1.
>
> Turns out that IBM's Java does not have the same implementation as Sun (now
> Oracle). I don't know about Android's Java, which seems to be a variant of
> Harmony.
>
> From a practical level this means that if there is a reliance on a specific
> version and comparable implementation of Unicode then one needs to stick
> with that. That is an index built with Java 1.4 may not be the same as one
> built with Java 5. And one built with Java 5 might not be the same as one
> built with Harmony/Android.
>
> This is especially true with Thai. IBM's Java does not have a decent break
> iterator while Sun's does. Who knows about Harmony? One way to get around
> this is to use ICU4J to do the analysis. And another is a UAX29Tokenizer,
> which tokenizes based on the Unicode tables (5.0 if I remember). With Lucene
> 3.0 and later, this is possible. And the code might be able to be back
> ported to 2.9.x series.
>
> Once tokens are identified, they are filtered. There are various filters
> that might be used (note, I'm doing this from memory so the names are a bit
> off. It will give the idea):
> LowercaseFilter - lower case the letters. Note, some languages don't have
> both upper and lower.
> FoldingFilter - removes accents, diacriticals, pointing and the like. There
> are some specific language foldings such as final sigma to sigma.
> CompoundWordFilter - splits compound words into parts. Very useful for
> German. Typically this is dictionary based.
> StopWordFilter - remove noise words such as a, the, in, ..., as provided in
> a list. From a theological perspective, "In Christ" might be an important
> find.
> *StemmingFilter - Converts word into their stem/root form. Note, this is
> language specific, thus the *. Generally this is rule based, but sometimes
> is dictionary driven.
> Note that the StandardAnalyzer filters stop words, but does no folding or
> stemming.
>
> ICU normalization generally needs to precede filtering. There are two basic
> forms: Composed (NFC) and decomposed (NFD). For each of these there is a
> canonical 'K' variant, NFKC and NFKD. Simplistically, with decomposed, the
> base character is followed by its decorations (e.g. accents). In composed
> form, they are combined into one. Our modules, in order to conserve space,
> typically do NFC.
>
> Some things to note:
> The order of filters may be important.
> The tables that the filters use are important.
>
> Each release of Lucene has varied one or more of these things. Typically,
> this is due to a bug fix.
>
> The goal is that a token stream for a field be the same for indexing as for
> searching. If they differ, results are unpredictable.
> So to put this together, if any of the following changes, all bets are off:
>     Tokenizer (i.e. which tokenizer is used)
>     The rules that a tokenizer uses to break into tokens.
>     The type associated with each token (e.g. word, number, url, .... We
> ignore this so it doesn't matter.)
>     Presence/Absence of a particular filter
>     Order of filters
>     Tables that a filter uses
>     Rules that a filter encodes
>     The version and implementation of Unicode being used (whether via ICU,
> Lucene and/or Java)
>     The version of Lucene (e.g. every version of Lucene has fixed bugs in
> these components.)
> And if we did highlighting:
>     The relative position of each token.
>
> What is planned is to record this along with the index in a manifest. If
> the manifest changes for a field that is exposed through the app, then the
> index should be rebuilt. It may be that JSword will be able to adapt to a
> particular manifest. For example, it is under programmers control whether
> stemming and/or stop filters are applied. (Right now, defaults are assumed.)
> If an index is built with stemming but not stop words, then the searching
> analyzer can be built to match. It won't matter that the list of stop words
> has changed.
>
> To have them on a server means that we need to keep versions around and to
> be able to request them. We need to support people who don't upgrade their
> app to match the latest index.
>
> Hope this is helpful.
>
> In Him,
>     DM
>
>
>
> On 11/04/2010 11:26 AM, Martin Denham wrote:
>
> Does anybody know any reason why a search for 'blessed' does not return any
> search results in ESV but searching for 'bless' work perfectly?
>
>  When I download  BibleDesktop (JSword) generated indexes to And Bible I
> have noticed that some searches like 'blessed' stop working but I can't
> figure out what the problem is and would appreciate some pointers as to
> areas to look.
>
>  I have checked that the correct Analyzer is being used but I am not sure
> what else to check or if the 'blessed'/'bless' issue might point to a
> specific problem area.
>
>  The plan is to download pre-created indexes to And Bible and in theory
> those indexes should be generated by JSword but currently And Bible can only
> use indexes it creates itself or which have been created by CLucene/Sword.
>
>  All advice, opinions, and comments are appreciated.
>
>  Many thanks
> Martin
>
>
>
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