RE: [EXI] Options Document Schema not clear

Santhanakrishnan,
 
Thank you for your questions regarding the EXI options document schema. The
EXI Options document schema was designed to produce very small EXI headers
for option combinations commonly used when compactness is critical. In
addition, it was designed to minimize the use of EXI built-in types to avoid
needlessly increasing the minimum code-footprint for small implementations
that don't otherwise require certain built-in EXI types. As such, most items
you expect to be Boolean or Enumerations are instead communicated by the
presence or absence of specific XML elements.
 
With these design criteria in mind, below are the answers to your specific
questions:
 
    1) The various options for alignment are represented by the presence or
absence of the <byte/> and <pre-compress/> elements. If <byte/> is present,
the alignment is byte-aligned. If <pre-compress/> is present, the alignment
is pre-compress. If both are absent, the alignment is bit-aligned.
 
    2) To satisfy the design criteria above, the presence of appropriately
named XML elements is used to indicate Boolean and enumerated values.
 
    3) Good catch. I apologize for this inconsistency. Strict will be
described in the 3rd public working draft of the EXI specification,
scheduled for release shortly. As of the time of the 2nd public draft,
strict was listed in Appendix F (Format Features Under Consideration), but
had not yet been added to the body of the specification.
 
For a better understanding of how the EXI options document works, I've
provided a few examples below. Based on your feedback, we will likely
include some examples in a future version of the spec. Thank you for this
feedback!
 
    All the best,
 
    John
 
Example #1: The following EXI options document specifies the default
options. This document is encoded in 3 bits (assuming strict mode):
 
  <header xmlns=" <http://www.w3.org/2007/07/exi>
http://www.w3.org/2007/07/exi">
  </header>
 
Example #2: The following EXI options document specifies EXI compression
should be used. This document is encoded in 8 bits (assuming strict):
 
<header xmlns="http://www.w3.org/2007/07/exi">
    <common>
        <compression/>
    </common>
</header>

Example #3: The following EXI options document specifies the body is an EXI
fragment, encoded with strict-mode and EXI compression. This document is
encoded in only 9 bits.
 
<header xmlns="http://www.w3.org/2007/07/exi">
    <common>
        <compression/>
        <fragment/>
    </common>
    <strict/>
</header>

Example #4: The following EXI options document specifies preservation of
comments and pis. It is encoded in 12 bits:
 
<header xmlns="http://www.w3.org/2007/07/exi">
    <lesscommon>
        <preserve>
            <comments/>
            <pis/>
        </preserve>
    </lesscommon>
</header>

Example #5: The following EXI options document specifies byte-alignment.
This document is encoded in 13 bits (assuming strict):
 
<header xmlns="http://www.w3.org/2007/07/exi">
    <lesscommon>
        <uncommon>
            <alignment>
                <byte/>
            </alignment>
        </uncommon>
    </lesscommon>
</header>




  _____  

From: public-exi-request@w3.org [mailto:public-exi-request@w3.org] On Behalf
Of santhanakrishnan
Sent: Friday, March 07, 2008 1:59 AM
To: public-exi@w3.org
Subject: [EXI] Options Document Schema not clear



Hi EXI WG,

       1) In the options document schema why precompress is a separate
element. The alignment value can be "bitpacked", "byte-aligned" or
"precompression" as per the specification. 

2) Also many of the elements take values of ComplexType though they take
some string or boolean value. 

3) The use of strict element is not explained anywhere in the spec.

Some examples for the options document can be useful in understanding.
Please help me with this ambiguities.

 

Regards

Santhanakrishnan