[
Lists Home |
Date Index |
Thread Index
]
Hmm, I'm sorry you don't think schema-based encoding is fair. I find it odd
that you regard schema-based (encoding) compression as lossy. This term is
normally associated with a permanent loss of information. Neither ASN.1 or
MPEG-7 result in the loss of XML content (the original content did not of
course contain the XML schema). The deployment of the schema upon which
encoding/decoding is based in a management issue. There is no need to
transmit it as part of the encoded content.
- Dan
> -----Original Message-----
> From: Elliotte Rusty Harold [mailto:elharo@metalab.unc.edu]
> Sent: Tuesday, March 11, 2003 10:01 AM
> To: winkowski@mitre.org; msc@mitre.org; xml-dev@lists.xml.org
> Cc: winkowski@mitre.org; msc@mitre.org
> Subject: RE: [xml-dev] XML Binary and Compression
>
>
> At 11:54 PM -0500 3/10/03, winkowski@mitre.org wrote:
>
> >On reflection, I don't think that the conclusions reached
> are all that
> >surprising. Redundancy based compression achieves better
> results as the file
> >size, and consequently the amount of redundancy, increases.
> CODECS that take
> >advantage of schema knowledge achieve efficient localized
> encodings and also
> >need not transmit metadata since this information can be
> derived at decoding
> >time.
>
> I may have missed something in your paper then, because I didn't
> realize you were doing this. If you're assuming that the same schema
> is available for both compression and decompression, then you're
> doing a lossy compression. The conmpressed forms of your documents
> have less information in them than the uncompressed forms. I don't
> consider that to be a fair or useful comparison with raw XML with
> metadata present.
>
> Then again, maybe that's not what you meant? If you're somehow
> embedding a schema in the document you transmit, then it's really
> just another way of compressing losslessly and that's OK, though In
> would still require that the schema used for compression be derived
> from the instance documents rather than applied pre facto under the
> assumption of document validity. Hmmm, that's not quite right. What I
> really mean is that given a certain schema it must be possible to
> losslessly encode both valid and invalid documents.
> --
>
> +-----------------------+------------------------+-------------------+
> | Elliotte Rusty Harold | elharo@metalab.unc.edu | Writer/Programmer |
> +-----------------------+------------------------+-------------------+
> | Processing XML with Java (Addison-Wesley, 2002) |
> | http://www.cafeconleche.org/books/xmljava |
> | http://www.amazon.com/exec/obidos/ISBN%3D0201771861/cafeaulaitA |
> +----------------------------------+---------------------------------+
> | Read Cafe au Lait for Java News: http://www.cafeaulait.org/ |
> | Read Cafe con Leche for XML News: http://www.cafeconleche.org/ |
> +----------------------------------+---------------------------------+
>
|
