We may or may not achieve quorum today because of the US holiday tomorrow and big travel day today.

I will join the call at 12noon US.ET, and if we have enough people by 12:05 then  I'd like to discuss one or more of these topics

* hexBinary and base64Binary  - I still find these confusing.
* array prefix and suffix - just review resolution of this issue - leaving out for now just to be conservative. Could put back in fairly easily.
* choiceType and length properties on xs:choice

My latest musings on hexBinary and base64Binary ....

E.g., XSD allows pattern and enumeration facets on these

     <element name="aThing" type="base64Binary" length="3"
                                                        pattern="AAAA|////" />

I think that pattern is a regexp for a base64 string matching 3 bytes of zeros or 3 bytes of all ones, but my regexp syntax is no doubt incorrectly escapified. ("A" is 6 bits of zero, "/" is 6 bits of 1 in base64).

To me this is marvelously confusing. It feels downright silly to allow pattern and enumeration on these things.

I'd like to adopt the strictest possible sensible thing.
   - hexBinary only, binary representation only, no pattern or enumeration facets supported or allowed for this type.  

There is still the issue of default/fixed.

E.g.,

     <element name="unknownStuff" type="hexBinary" fixed="F41306C0" dfdl:lengthKind="implicit" />

The user specifies what the bytes are as a hex string, and since they said it's hexBinary, they use hex to express the literal content. This is a way to say "right here in the data there's this blob of stuff I don't understand, but it always contains these data bytes". I've certainly seen the need for this sort of thing. It's being ignored on input, but on output it generates the fixed bytes of data so as to create valid output even when you don't understand this part of the data format. In fact, the cases I've seen are using this to skip over decimal numbers the wierd format of which isn't understood. The above pattern could be one or more decimal numbers in strange formats.

However, I can see the slippery slope from here to allowing pattern and enumeration facets, so I'd be happy ruling out use of default and fixed on hexBinary type also, just to make it even simpler.

Also, this element achieves the same end using our "%" escapes in strings.

   <element name="unknownStuff" type="string" dfdl:encoding="ascii" fixed="%F4%13%06%C0"  dfdl:lengthKind="implicit"/>

This works for any single-byte-wide character-set encoding.



Mike Beckerle
STSM, Architect, Scalable Computing
IBM Software Group
Information Platform and Solutions
Westborough, MA 01581
direct: voice and FAX 508-599-7148
assistant: Pam Riordan  
                 priordan@us.ibm.com
                 508-599-7046