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Re: [ANN] Nemo (i.e. why I wrote Nemo)

From: Lisa Seeman <lisa@ubaccess.com>
Date: Wed, 08 Dec 2004 09:59:36 +0200
To: James Cerra <jfcst24_public@yahoo.com>, Laurian Gridinoc <laurian@gmail.com>
Cc: www-rdf-interest@w3.org
Message-id: <018501c4dcfc$1b20f2f0$680aa8c0@IBMA4E63BE0B9E>
FYI
if you are planning to since I plan on embedding RDF data directly into
documents. There is a draft for XHTML 2.0 for embedding RDF into the body of
the document using the Link element.

They are thinking of some other mechanisms too, but I think Link was the
most powerful proposal.


Keep well
Lisa

  ----- Original Message ----- 
  From: James Cerra
  To: Laurian Gridinoc
  Cc: www-rdf-interest@w3.org
  Sent: Tuesday, November 30, 2004 6:40 PM
  Subject: Re: [ANN] Nemo (i.e. why I wrote Nemo)



  Laurian Gridinoc,

  Wow, thank's for the skinnny on 3Store and
  Triplestore.  It seems very impressive (more than
  anything I'd come up with).  Your stylesheet was also
  pretty insightful [1].

  To answer your question, the other well-known programs
  to query arbitrary RDF datastores include:

    * RDF Twig [2]
    * Treehugger [3]

  There has been more work done; however most of the
  other approaches only transform a subset or
  "normalized" form of RDF/XML [4, 5, 6].

  IMHO, there are a few issues with the design of
  Treehugger and RDF Twig (and Triplestore, from an
  initial look):

    * I don't think that XPath by itself should be used
  to query RDF.  It was designed for searching trees and
  not arbitrary graphs.  So RDF Twig, Treehugger, and
  others reserialize the graph into documents that are
  easier to use with XPath.  However, this makes it hard
  to construct queries if you don't know the details of
  the initial serialization.  (i.e. Should I query for
  ./@rdf:resource or ./rdf:resource?)

    * The results are returned as another XML document
  or XML fragment.  This means that another tree has to
  be built - isn't that inefficient?  If there are a lot
  of nodes queried, this could mean a lot of memory is
  used.

    * They seem to concentrate on quereies stored in
  seperate files.  For my purposes, it is more
  advantageous to query rdf data that is embedded in a
  file.

  Nemo uses Jena to do all of the querying, so any
  improvements to RDQL are passed along to my app.  RDF
  Twig also allows generic Jena queries to be passed to
  it; however, I really don't like the interface (an
  entire extension element makes no sense to me - I
  intend to add convience functions to Nemo to create
  query strings easier in an XML file).

  Nemo also returns the results of a query as an
  iterator that lazily evaluates each query only when
  the XSLT processor uses it.  This saves resources (I
  hope) when accessing large datastores.

  Furthermore, Nemo allows rdf/xml to be retrieved from
  a branch of the XML document rather than a seperate
  document.  This is important, since I plan on
  embedding RDF data directly into my documents.

  That's why I wrote Nemo.

  --
  Jimmy Cerra

   "my mind is slipping away... day by glorious day"
    - Robin A. Gorkin

  --
  [1] I'd never think in XSLT to use a variable
  containing a string as a hash.

  [2] http://rdftwig.sourceforge.net/

  [3] http://rdfweb.org/people/damian/treehugger/

  [4]

http://www.wasab.dk/morten/blog/archives/2004/05/30/transforming-rdfxml-with-xslt

  [5] http://www.w3.org/2001/12/rubyrdf/xsltrdf/

  [6] http://www.w3.org/XML/2000/04rdf-parse/




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Received on Wednesday, 8 December 2004 08:01:55 GMT

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