I'll tell you what I'm planning to do inside of a few weeks in the daffodil project, since we have a community that has lots of binary data with illegal XML chars in it, who view XML interchange as their primary use case since complex validation follows DFDL processing, and that occurs on XML data.

I'm planning to provide two functions in the function library

daffodil:translateIllegalXMLCharsToPUA(arg) : xs:string
daffodil:translatePUAToIllegalXMLChars(arg) : xs:string

These take any of the illegal XML codepoints between 0x00 and 0x20, and add 0xE000 to their codepoint value to put them into the private use area (PUA) codepoints so as to preserve their information content.

These functions can be used inside of inputValueCalc and outputValueCalc to deal with strings that have these illegal xml codepoints in them.

Might also provide an implementation specific property: daffodil:encodingModifiers="translateIllegalXMLCharsToPUA" which is a list of implementation specific flag/modifier strings. This one would mean that all strings are to be treated in this way when parsing, and the inverse when unparsing.

For now, this will work only for single-byte encodings. It will be a schema-def error if you use it with a multi-byte encoding or variable-width encoding like utf-8.





On Thu, Nov 1, 2012 at 11:13 AM, Suman Kalia <kalia@ca.ibm.com> wrote:
Agree . XML is an important use case..   We certainly want to provide guide guidance to the user on how to do.  If we can standardize, it would be great...

Suman Kalia
IBM Canada Lab
WMB Toolkit Architect and Development Lead
Tel: 905-413-3923 T/L 313-3923
Email: kalia@ca.ibm.com

For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html





From:        Mike Beckerle <mbeckerle.dfdl@gmail.com>
To:        Suman Kalia/Toronto/IBM@IBMCA,
Cc:        Steve Hanson <smh@uk.ibm.com>, dfdl-wg@ogf.org
Date:        11/01/2012 11:08 AM
Subject:        Re: [DFDL-WG] proposal: DFDL needs additional function dfdl:characterCode



I think all implementations will have to solve this problem. XML interchange is an important use case.

The question is just whether the DFDL standard says exactly how to do it or we leave it up to implementations and standardize an approach later.

...mike
On Thu, Nov 1, 2012 at 9:25 AM, Suman Kalia <kalia@ca.ibm.com> wrote:
 I have an xsd element of type string , the text data pertaining to it  is as in Mike's example ..  What I infer from your note is that in DFDL infoset , the string will appear as such    ie. 123<0>456<1>789<2>123l.    It is up to the user to parse this string and handle syntactic characters if he wants to render this in XML ??  

 
Suman Kalia
IBM Canada Lab
WMB Toolkit Architect and Development Lead
Tel: 905-413-3923 T/L 313-3923
Email: kalia@ca.ibm.com

For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html





From:        Steve Hanson <smh@uk.ibm.com>
To:        Suman Kalia/Toronto/IBM@IBMCA,
Cc:        dfdl-wg@ogf.org
Date:        11/01/2012 09:07 AM
Subject:        Re: [DFDL-WG] proposal: DFDL needs additional        function        dfdl:characterCode




If you use XML-specific entity references then you have forced all consumers of the DFDL Infoset to be XML aware. The DFDL infoset is (deliberately) not an XML infoset. If I am parsing a string that contains x'08' there is nothing intrinsically wrong with that code point. It's only a problem if it is subsequently serialised as XML.  (If we wanted to have an XML focus to the DFDL infoset then we would have gone down the XDM route, an approach which was rejected).

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848



From:        Suman Kalia <kalia@ca.ibm.com>
To:        Steve Hanson/UK/IBM@IBMGB,
Cc:        dfdl-wg@ogf.org, dfdl-wg-bounces@ogf.org, Mike Beckerle <mbeckerle.dfdl@gmail.com>
Date:        01/11/2012 12:47
Subject:        Re: [DFDL-WG] proposal: DFDL needs additional        function        dfdl:characterCode



Shouldn't we be using entity references for XML syntactic character  found in text/binary data while creating info set and vice versa...

Suman Kalia
IBM Canada Lab
WMB Toolkit Architect and Development Lead
Tel: 905-413-3923 T/L 313-3923
Email: kalia@ca.ibm.com

For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html





From:        Steve Hanson <smh@uk.ibm.com>
To:        Mike Beckerle <mbeckerle.dfdl@gmail.com>,
Cc:        dfdl-wg@ogf.org
Date:        11/01/2012 07:57 AM
Subject:        Re: [DFDL-WG] proposal: DFDL needs additional        function        dfdl:characterCode
Sent by:        dfdl-wg-bounces@ogf.org



>From WG call minutes 2012-10-30:

"Beyond the scope of DFDL 1.0.  Assumption for now is that infoset needs post-processing."

Mike has observed that other software systems  "map the illegal characters to/from the Unicode Private Use Area."

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848



From:        Mike Beckerle <mbeckerle.dfdl@gmail.com>
To:        dfdl-wg@ogf.org,
Date:        04/10/2012 23:39
Subject:        [DFDL-WG] proposal: DFDL needs additional function        dfdl:characterCode
Sent by:        dfdl-wg-bounces@ogf.org




An important use case for DFDL is converting legacy data to/from XML.

XML 1.0 disallows a bunch of string characters.

If the data contains those characters, then the question arises of what to turn them into that both preserves information content, but also is legal in XML so that you can convert the DFDL infoset into XML without violating XML's constraints.

The natural thing to do is create an element containing the character code of the illegal character, as an integer.

E.g., character code U+0001 would become an element. Such as:  <ccode>1</ccode>.

This could be done using a hidden element that is a string, and the element ccode above would have an inputValueCalc that converts the offending character of that string into an integer.

But we need a function dfdl:characterCode(str, pos) : int

The arguments would be a string, and a position (base 1) within that string, and the return result would be the character code of the character in the string at that position. If pos is out of the bounds of the string (i.e., is negative, 0, or too large), then a processing error would occur.

For unparsing the inverse function would also be needed: dfdl:character(intArg) : string. This would return a string containing one character whose codepoint is the intArg.

Example

Consider this data:
 123<0>456<1>789<2>123l
where <0> means just one character with codepoint  0, etc.

In hex that would be 313233 00 343536 01 373839 02 313233

The best I can think of for modeling this while preserving all information would end up with XML looking like this:

<nonXMLString>
<fragment><stringData>123</stringData></fragment>
<fragment><nonXMLChar><charCode>0</charCode></nonXMLChar></fragment>
<fragment><stringData>456</stringData></fragment>
<fragment><nonXMLChar><charCode>1</charCode></nonXMLChar></fragment>
<fragment><stringData>789</stringData></fragment>
<fragment><nonXMLChar><charCode>2</charCode></nonXMLChar></fragment>
<fragment><stringData>123</stringData></fragment>
</nonXMLString>

So our nonXMLString is of a type which is array of fragment, a fragment is a choice of either (legal XML) stringData, or a nonXMLChar.

The nonXMLChar has a child element because it will need to convert to from a string so will use inputValueCalc and outputValueCalc to do so, so it needs to be a sequence so that it can have the other hidden elements needed to pull this off.

stringData would have lengthKind="pattern" and a pattern that allows any sequence of XML-allowed characters.

nonXMLChar would have a hidden first child element of type string of explicit length 1 with an assertion that the string match a pattern that is any of the illegal characters (but just one of them). The charCode child element would inputValueCalc to get the character code of the character. For 8 bit encodings it would be ok as a table lookup in XPath, but for unicode..... we'd need a function that returns a character code.

If you just have one embedded illegal character, like NUL, then you could just model it as a separator, which would simplify things considerably (and is possible in a someday XML 1.1 future since NUL is then the only disallowed character.)

But for XML 1.0's illegal characters, we need to be able to convert to/from some non-string representation if we are to preserve information content. Hence we need these additional functions.

--
Mike Beckerle | OGF DFDL WG Co-Chair
Tel:  781-330-0412
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--
Mike Beckerle | OGF DFDL WG Co-Chair 
Tel:  781-330-0412



--
Mike Beckerle | OGF DFDL WG Co-Chair 
Tel:  781-330-0412