[Nepomuk] [RFC] Better Full text search

Thu May 9 09:51:02 UTC 2013

Hi,

I see several problems with this implementation: performance, reliability
and maintenance.

Variable string fields are not designed for performance, only to store
variable size text, so I'm a little bit worried about performance when
there is a large data stored in it. If we are trying to create something
like an index, an oversized index it's not a good solution. Someone
suggested to ask Virtuoso developers and this is a good idea because they
can confirm, or not, this point.

Reliability it's another problem because, what information are you planning
to store?. In my case I'm using extensively nao:altLabel to locate
resources: Hyo Jung Kim, Hyolin, Hyolyn, Hyorin, 김효정, 효린 are all valid
names for nco:fullname 효린 (Hyorin). With music there is a lot of
information available that could be interested when you are searching:
album artist, director, lyricist or composer so you must add this
information or full text search will be limited to the indexed values.
Other example are comments, I'm using it sometimes to search photographs,
because it's easy to handle with Dolphin so probably others are doing the
same with photos or with other stuff. By the way, you need to add tags
label too or full text search will fail. In brief, if you add large data
performance will be affected but if you add few data reliability will be
affected.

Maintenance is the thirth problem and this could be a big problem if there
are many information stored in this field because every time you updated a
resource you must rebuild, because it's unformated, this field for all
resources involved so you can't use this ontology to store any manual
information. Actually Bangarang and Nepoogle allow update resources, a
common feature for a database, so if you are storing album artist and I
update the nco:Contact you must update all music pieces related to this
album artist or full text search will fail.

I read some comments about Nepomuk it's not a data store that concern me.
I'm using Nepomuk as a data store extensively, tags, comments, rating and
other stuff using Nepoogle, because without it Nepomuk less more useful for
me and, honestly, I can't understand it without this functionality. Some
time ago some effort was spend explaining that Nepomuk it's not a file
search so don't transform it in a resources search tool.

Finally, about lyrics stuff, seems like nie:plainTextContent is the right
place to store text representation of an audio, and probably will be the
right place to store video subtitles, both as a cache and as a method to
search so seems like this ontology will be like Marx Brothers cabin scene
in A Night at the Opera :).

An as usual sorry for my Engrish :).

On Sat, May 4, 2013 at 7:09 PM, Vishesh Handa <me at vhanda.in> wrote:

>
>
>
> On Sat, May 4, 2013 at 9:18 PM, <phreedom at yandex.ru> wrote:
>
>> On Суббота 04 мая 2013 20:14:37 Vishesh Handa wrote:
>> > On Sat, May 4, 2013 at 7:47 PM, Ivan Čukić <ivan.cukic at kde.org> wrote:
>> > > > <res> nie:plainTextContent "title artist album whatevereElse" .
>> > >
>> > > For me, the plainTextContent of a song would be the lyrics. This seems
>> > > like a
>> > > misuse of the property. With a very good reason behind it, but still a
>> > > misuse.
>> > >
>> > > I remember when I wanted to keep all activities in one string
>> property as
>> > > a \n
>> > > terminated list to make it speedy :D
>> > >
>> > > I'd say go for it, but only as a last resort.
>> >
>> > I would not like Nepomuk to be a data store. It's not the place to store
>> > your lyrics to fetch them later, same for emails and files. It is a
>> place
>> > to store structured data.
>> >
>> > In the case of lyrics, the main reason we are storing them is to be
>> able to
>> > be search through them, not to display them to the user. So we can
>> > potentially append other data.
>>
>> Yes and no.  Until discardable graphs were introduced, there was even no
>> distinction between primary storage and cached stuff. The real life is
>> even
>> more complicated, you can have local data indexed, you can have  remote
>> data
>> indexed(and it would be very very nice to have it cached) and for some
>> tuff
>> nepomuk is used as the primary storage.
>>
>> The reason people are trying to stuff nepomuk with their blobs is very
>> simple:
>> there's a very real demand for this functionality and nepomuk ontologies
>> as-is
>> already allow you to store your whole filesystem, including all byte
>> streams/file contents, so it looks like a very reasonable approach,
>> especially
>> since nobody actually offers an alternative. Ok akonadi is the only
>> exception
>> which provides caching of remote data but it's domain-specific.
>>
>> Imagine a user finding a music video by its lyrics, opening the video
>> only to
>> discover that (s)he can't see any lyrics, because nepomuk got its lyrics
>> from
>> some web extractor. Thus the motivation to use nepomuk at least as a
>> cache of
>> data, not only for search purposes.
>>
>
> You do have a point. In this case they should be able to access the lyrics.
>
>>
>> There's no primary storage for user-generated rdf at all, so the data is
>> stored in nepomuk and users are disappointed when something breaks or
>> disappears.
>>
>
> If we treat Nepomuk as a data store, then you have to deal with keeping
> the store up to date. Specifically in the case of Akonadi - what are
> applications supposed to use? Nepomuk or Akonadi? And then we also need a 2
> way sync to keep both the databases up to date.
>
> So I prefer treating Nepomuk as a cache just for searching, but I get that
> it isn't in the case of tags, and ratings, and other specific rdf. So it's
> weird.
>
>
>> I'm currently experimenting with solutions to some of these issues, but I
>> can't do it fast due to time constraints. I don't expect anything worth
>> going
>> public with in the next couple of months at least and that's if I'm lucky
>> :(
>>
>
> Could you elaborate?
>
>
>> _______________________________________________
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>> Nepomuk at kde.org
>> https://mail.kde.org/mailman/listinfo/nepomuk
>>
>
>
>
> --
> Vishesh Handa
>
> _______________________________________________
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>
>

-- 
Best wishes,
Ignacio
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