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From "Andrzej Bialecki (JIRA)" <j...@apache.org>
Subject [jira] Commented: (NUTCH-139) Standard metadata property names in the ParseData metadata
Date Sat, 07 Jan 2006 08:25:57 GMT
    [ http://issues.apache.org/jira/browse/NUTCH-139?page=comments#action_12362049 ] 

Andrzej Bialecki  commented on NUTCH-139:
-----------------------------------------

I see three issues here:

* using standard metadata names and handling misspelles/erroneous ones: this patch provides
this function, and IMO does it well.

* providing authoritative values for certain metadata, if the original ones are absent of
not trustworthy. Well, this patch provides this functionality, but with a twist, i.e. we say
that the earliest values are the ones coming from the protocol level, later ones from parse
or other plugins, and the latest value on top is the one that should be used for the further
processing. That's what is meant by "history".

* supporting multi-values headers: I don't see how this patch could possibly support it, because
it re-defined the semantics of multiple values per key ("history" - see above). So, it doesn't
support multi-values per key, and I don't see any easy way how to add this support later,
without creating a messed up mix of "historical" and "multi" values...

> Standard metadata property names in the ParseData metadata
> ----------------------------------------------------------
>
>          Key: NUTCH-139
>          URL: http://issues.apache.org/jira/browse/NUTCH-139
>      Project: Nutch
>         Type: Improvement
>   Components: fetcher
>     Versions: 0.7.1, 0.7, 0.6, 0.7.2-dev, 0.8-dev
>  Environment: Power Mac OS X 10.4, Dual Processor G5 2.0 Ghz, 1.5 GB  RAM, although bug
is independent of environment
>     Reporter: Chris A. Mattmann
>     Assignee: Chris A. Mattmann
>     Priority: Minor
>      Fix For: 0.7.2-dev, 0.8-dev, 0.7.1, 0.7, 0.6
>  Attachments: NUTCH-139.060105.patch, NUTCH-139.Mattmann.patch.txt, NUTCH-139.jc.review.patch.txt
>
> Currently, people are free to name their string-based properties anything that they want,
such as having names of "Content-type", "content-TyPe", "CONTENT_TYPE" all having the same
meaning. Stefan G. I believe proposed a solution in which all property names be converted
to lower case, but in essence this really only fixes half the problem right (the case of identifying
that "CONTENT_TYPE"
> and "conTeNT_TyPE" and all the permutations are really the same). What about
> if I named it "Content     Type", or "ContentType"?
>  I propose that a way to correct this would be to create a standard set of named Strings
in the ParseData class that the protocol framework and the parsing framework could use to
identify common properties such as "Content-type", "Creator", "Language", etc.
>  The properties would be defined at the top of the ParseData class, something like:
>  public class ParseData{
>    .....
>     public static final String CONTENT_TYPE = "content-type";
>     public static final String CREATOR = "creator";
>    ....
> }
> In this fashion, users could at least know what the name of the standard properties that
they can obtain from the ParseData are, for example by making a call to ParseData.getMetadata().get(ParseData.CONTENT_TYPE)
to get the content type or a call to ParseData.getMetadata().set(ParseData.CONTENT_TYPE, "text/xml");
Of course, this wouldn't preclude users from doing what they are currently doing, it would
just provide a standard method of obtaining some of the more common, critical metadata without
pouring over the code base to figure out what they are named.
> I'll contribute a patch near the end of the this week, or beg. of next week that addresses
this issue.

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