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[smila-dev] Re: [Aperture-devel] usage of extractors
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It was Daniel.Stucky@xxxxxxxxxxx who said at the right time 05.12.2008
14:08 the following words:
Hi aperture team,
I have another question concerning the usage of extractors:
As I understand - Extractor implementations register their factory at
the ExtractorRegistry. Each ExtractorFactory provides a list of
supported mimetypes it can extract. The ExtractorRegistry returns
available Extractors for a specified mimetype or a set of all registered
Extractors.
uh, nearly.
The ExtractorFactories are registered at the ExtractorRegistry.
The registry returns Factories, not Extractors.
A factory returns an extractor.
(=the usual Elfish art of frameworking)
How is it possible to select a certain Extractor to use for document
extraction if multiple extractors are available for the specified
mimetype? Is such a selection logic part of the implementation of a
smila pipelet using the aperture extractor ?
It is not possible, and its a mumbo-jumbo.
When two extractors are registered for a mime-type, there is no ranking
or rating of them.
basically, three ways how you can solve it in SMILA (=in aperture we
will probably leave it open)
* do not allow multiple extractors (=the best solution !)
* rank them from generic - to - specific: a "any file" extractor has a
specific rate of "0.1", a PDF extractor that knows how to scan the text
for titles and whatever is "1.0", but "1.0" only for "PDFs generated
from Latex and using titles". This is TRICKY
* have both extractors run, mix the results (easy)
for the last: "have both extractors run, mix the results"
this is implemented in nepomuk, mixing the result is easy - because we
use RDF.
the magic lines of code are:
http://dev.nepomuk.semanticdesktop.org/browser/trunk/java/org.semanticdesktop.nepomuk.comp.datawrapper.aperture/src/org/semanticdesktop/nepomuk/comp/datawrapper/aperture/impl/ApertureDataWrapperCrawlerHandler.java#L512
http://dev.nepomuk.semanticdesktop.org/browser/trunk/java/org.semanticdesktop.nepomuk.comp.datawrapper.aperture/src/org/semanticdesktop/nepomuk/comp/datawrapper/aperture/impl/ApertureDataWrapperCrawlerHandler.java#L550
in the second part, we can safely run multiple extractors on one stream,
because we buffered it before (into a file).
you can think of better schemes, of course...
best
Leo
Bye,
Daniel
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