[Nepomuk] [RFC] Better Full text search

Thu May 9 11:46:47 UTC 2013

On Thu, May 9, 2013 at 3:21 PM, Ignacio Serantes <kde at aynoa.net> wrote:

>
>> Yeah. I was just thinking about the file indexer. If you incorporate the
> web-miner, then it would be the web-miner's responsibility to update the
> full text index (or nie:plainTextIndex) for the resource who it attaches
> resources to.
>

You can't expect this. Nepomuk it's the middleware so this is a Nepomuk's
job and you can't trust that your clients follow right logic because logic
could change. For example, nepomuk webminer could be abandoned or some
users could still use Bangarang that seems abandoned. Even worse, some
distros could be packaging and old version without your required changes,
for example openSUSE still is packaging webminer but the old version.

You can use clients to process data (sorting, filtering, etc...) but all
business logic must be written in the middleware and never in the clients.

>
>> 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.
>>
>
> I was hoping it would be more of a full text + structured data storage
> tool. It is not a place to store plain text such as the file's contents and
> expect to get them back exactly as they were.
>

No, but you want to store any kind of metadata and retrieve information.

> I'm worried that if we do not put all the plain text in one place we
> cannot reliably solve the searching problem. Users mostly just provide
> plain text when searching. They just provide words "blah blah blah". Most
> users would not know about higher semantics such as "hasTag:" or
> "performer:". That's only for more technical users.
>

The main problem here is the lack of a proper search interface. There was
one in KDE 4.5, I learned about hastag and other stuff that days, but was
removed. Maybe with this year's GSOC we have one.

> Doing a search through for x words leads 2x unions which is very very
> slow. In the case I highlighted in the first email, it takes a good 26
> seconds on my system. That's just too slow. The user expects feedback in
> MAX a second. Generally, even less than a second.
>

Yes, I know it but where are you doing this search? In Dolphin or KRunner?
Then maybe something like mail:"my search text" could be useful to optimize
this kind of search. Consider that most of the time you can optimize
queries if you guide user but, it's true, full text search always will be
slow :). In applications, like KMail, you can always add right filters to
optimize the search.

>
> Do you have any suggestions on how to fix that?
>

Sadly I don't know how to optimize this in triplestore databases, with
relational databases you use views and indexes but you can't use it here.
Maybe Virtuoso people could help you.

>
> Additionally, with the query I showed above you also have a problem of
> stuff like this -
>
> res a nmm:MusicPiece .
> nmm:MuiscPiece rdfs:comment "Used to assign music-specific properties such
> a BPM to video and audio"
>
> searching for 'assign music' can give me music results which have nothing
> to do with music. I'm not sure how to solve this.
>

You can't, a full text search it's a full text search :).

>
> If we want to change how plain text is stored now is the time to do
> because with the 4.11 release most users will already have to re-index all
> their files and PIM data.
>

When 4.11 will be released? This is not a trivial change and must be tested.

>
> [1] http://xapian.org/
>
>>
>>
>> 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?
>>>
>>>
>>>> _______________________________________________
>>>> Nepomuk mailing list
>>>> Nepomuk at kde.org
>>>> https://mail.kde.org/mailman/listinfo/nepomuk
>>>>
>>>
>>>
>>>
>>> --
>>> Vishesh Handa
>>>
>>> _______________________________________________
>>> Nepomuk mailing list
>>> Nepomuk at kde.org
>>> https://mail.kde.org/mailman/listinfo/nepomuk
>>>
>>>
>>
>>
>> --
>> Best wishes,
>> Ignacio
>>
>>
>> _______________________________________________
>> Nepomuk mailing list
>> Nepomuk at kde.org
>> https://mail.kde.org/mailman/listinfo/nepomuk
>>
>>
>
>
> --
> Vishesh Handa
>

-- 
Best wishes,
Ignacio
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