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Re: Feedback of EXI specification 1

From: Jaakko Kangasharju <jkangash@cc.hut.fi>
Date: Thu, 08 Jan 2009 15:59:58 +0200
To: ISHIZAKI Tooru <ishizaki.tooru@canon.co.jp>
Cc: public-exi-comments@w3.org, youenn.fablet@crf.canon.fr, fujisawa.jun@canon.co.jp
Message-ID: <863aftgaox.fsf@cc.hut.fi>

ISHIZAKI Tooru <ishizaki.tooru@canon.co.jp> writes:

> Dear EXI members,
> In chapter 5.4(EXI Options), alignment option and EXI compression
> option can be unified.
> Then option values are
>  - bit-packed, byte-alignment, pre-compression, compression
> If doing so, the implementation will be more simple.

Hello Tooru,

Thank you for your comment. You are correct in that the four options
you present are the only possible ones from the alignment-compression

The reason why alignment and compression are separated as options is
to achieve better compactness for the EXI Options header. It is
expected that EXI compression is used often, so it is placed in the
"common" part of the Options header, whereas the non-default alignment
options are expected to be used only in very special circumstances and
are therefore placed in the "uncommon" part. This reduces the size of
the Options header in the usual case when the default alignment is

But none of this prescribes any particular implementation strategy. An
implementation is free to adopt the approach that you suggest,
including in its API, as long as it produces and is able to consume
correct Options headers.

Hope this helps,

Jaakko Kangasharju, Helsinki University of Technology
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Received on Thursday, 8 January 2009 14:01:44 UTC

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