[DFDL-WG] Fw: A gap in the behaviour for when escapeKind=escapeBlock

[Steve Hanson]

Agreed on processing error. Erratum raised, tracked here: 
http://redmine.ogf.org/issues/230

Regards
 
Steve Hanson
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh at uk.ibm.com
tel:+44-1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 23/09/2014 15:40 -----

From:   Steve Hanson/UK/IBM
To:     Mike Beckerle <mbeckerle.dfdl at gmail.com>, 
Cc:     Andrew Edwards/UK/IBM at IBMGB, "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>, 
dfdl-wg-bounces at ogf.org
Date:   09/09/2014 15:57
Subject:        Re: [DFDL-WG] A gap in the behaviour for when 
escapeKind=escapeBlock


I think that is still ambiguous. 

I prefer a processing error - data is not compliant with escape scheme.

Regards
 
Steve Hanson
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh at uk.ibm.com
tel:+44-1962-815848



From:   Mike Beckerle <mbeckerle.dfdl at gmail.com>
To:     Andrew Edwards/UK/IBM at IBMGB, 
Cc:     "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>
Date:   09/09/2014 15:44
Subject:        Re: [DFDL-WG] A gap in the behaviour for when 
escapeKind=escapeBlock
Sent by:        dfdl-wg-bounces at ogf.org



Now that's a really good catch.

Is it sufficient to say the EEC is escaped if it is last in the data to 
avoid creating the escaped block end?



Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | 
www.tresys.com
Please note: Contributions to the DFDL Workgroup's email discussions are 
subject to the OGF Intellectual Property Policy


On Mon, Sep 8, 2014 at 12:05 PM, Andrew Edwards <andy.edwards at uk.ibm.com> 
wrote:
While working in the escapeBlock area, I seem to have found a gap in the 
definition for DFDL's behaviour when using escape blocks. 

>From section 13.2.1, relevant extracts are: 
When 'escapeBlock': On unparsing the entire data are escaped by adding 
dfdl:escapeBlockStart to the beginning and dfdl:escapeBlockEnd to the end 
of the data. The data is either always escaped or escaped when needed as 
specified by dfdl:generateEscapeBlock. If the data is escaped and contains 
the dfdl:escapeBlockEnd then first character of each appearance of the 
dfdl:escapeBlockEnd is escaped by the dfdl:escapeEscapeCharacter. 
and 
On parsing the dfdl:escapeBlockStart string must be the first characters 
in the (trimmed) data in order to activate the escape scheme. The 
dfdl:escapeBlockStart string is removed from the beginning of the data. 
Until a matching dfdl:escapeBlockEnd string (that is, one not preceded by 
the dfdl:escapeEscapeCharacter) is found in the data, any in-scope 
terminating delimiter encountered in the data is not interpreted as such, 
and any dfdl:escapeEscapeCharacters are removed when they precede an 
dfdl:escapeBlockEnd string. 

Now consider a a model where: 
escapeBlockStart="start" 
escapeBlockEnd="end" 
escapeEscapeCharacter="#" 

Then take a logical value of: 
A hash is a # 

When we serialize the value, we wrap the value with the escapeBlockStart 
and escapeBlockEnd, and we preceed any instance of the escapeBlockEnd 
within the data with an escapeEscapeCharacter.  This then gives us the 
physical value "startA hash is a #end".  If we were to parse that data, we 
see the "#end" as an escaped escapeBlockEnd and report that there is no 
escapeBlockEnd. 

The gap in the behavioural definition seems to be that the specification 
makes no claim to do anything to escape an instance of an 
escapeEscapeCharacter when serializing;  There is nothing to catch the 
case of an escapeEscapeCharacter that isn't escaping an escapeBlockEnd but 
ends up doing it by circumstance. 



Andy 

Andy Edwards - IBM Integration Bus - DFDL 


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741598. 
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
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