Let me start answering my own question by way of these two definitions found in the XSD spec:

The ·value space· of hexBinary is the set of finite-length sequences of binary octets.

The ·value space· of base64Binary is the set of finite-length sequences of binary octets.

Note that the value of these is not some sort of encoded string form. I.e., hexBinary values do not involve characters 0-9A-F, rather. It's the octets that are the value.

To me this means that hexBinary and base64Binary are really identical in DFDL, except if we provide some sort of expressions for converting them to/from strings in that case the conversions are different and produce/consume different strings.

...mike

Mike Beckerle/Worcester/IBM@IBMUS
Sent by: dfdl-wg-bounces@ogf.org

11/16/2007 04:23 PM

To	dfdl-wg@ogf.org
cc
Subject	[DFDL-WG] DFDL infoset and hexBinary

What is the DFDL infoset value for a hexBinary type element?

Our doc says an element of type hexBinary has a value member in the infoset whose type is a hexBinary, but what is a hexBinary anyway?

Consider this 12 bytes of data, dumped here as hex: 003100320033004100420043

If that's a string in UTF-16BE encoding, it looks like "123ABC"

It is 12 bytes long.

Suppose we describe this using this DFDL:

<element name="a" type="hexBinary" length='12' />

As I understand it, this is correct XSD in that the length of a hexBinary is always specified as the number of 'octets' of the binary data, not characters.

Now, the contents of the basic XML infoset for an element matching this schema are these 24 characters: "003100320033004100420043". This is because the XML infoset has no idea what this string is because it is not schema aware.

An XML document corresponding to this might look like:

<! xml version='1.0' encoding="UTF-16BE" !>
<a>003100320033004100420043</a>

So, the question is......

What are the contents of the DFDL Infoset for a hexBinary like this? Same 24 characters? or 12 'octets' of data?

This is essentially the answer to the question "what IS a hexBinary?" or maybe "what is a hexBinary in the PSVI other than just a string?"

...mikeb -- dfdl-wg mailing list dfdl-wg@ogf.org http://www.ogf.org/mailman/listinfo/dfdl-wg