[DFDL-WG] Can I concatenate a variable?

[Tim Kimber]

There is no way to vary the pattern depending on the value of a variable 
unless you have a limited number of possible patterns.  In that case you 
could use the variable ( in the expression for a DFDL discriminator ) to 
discriminate a choice where each branch of the choice has a different DFDL 
regular expression.

However, I think you need more flexibility than that - the boundary string 
could be just about anything, right?. The 
dfdl:initiator/separator/terminator properties do take a DFDL expression, 
and it should be possible to model a wide range of data formats using 
those properties. Is there some reason why that is not possible in your 
case?

regards,

Tim Kimber, DFDL Team,
Hursley, UK
Internet:  kimbert at uk.ibm.com
Tel. 01962-816742 
Internal tel. 37246742




From:   "Garriss Jr., James P." <jgarriss at mitre.org>
To:     "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>, 
Date:   25/06/2013 12:38
Subject:        Re: [DFDL-WG] Can I concatenate a variable?
Sent by:        dfdl-wg-bounces at ogf.org



> In section 12.3.5 of the specification, the 'lengthPattern' property is 
listed as having the type 'DFDL Regular expression'. Unlike some other 
properties, dfdl:lengthPattern cannot be a DFDL expression. Therefore it 
cannot contain a DFDL variable reference.
 
Is there no workaround for this?
 
From: dfdl-wg-bounces at ogf.org [mailto:dfdl-wg-bounces at ogf.org] On Behalf 
Of Tim Kimber
Sent: Monday, June 24, 2013 4:11 PM
To: dfdl-wg at ogf.org
Subject: Re: [DFDL-WG] Can I concatenate a variable?
 
Hi James, 

In section 12.3.5 of the specification, the 'lengthPattern' property is 
listed as having the type 'DFDL Regular expression'. Unlike some other 
properties, dfdl:lengthPattern cannot be a DFDL expression. Therefore it 
cannot contain a DFDL variable reference. 

On the other hand, section 14.2 lists the data type of dfdl:separator as 
'List of DFDL String Literals or DFDL Expression', However, your 
dfdl:separator is not a valid DFDL expression. The property must be either 
a valid DFDL expression or a list of DFDL string literals. The syntax you 
need is 

<xsd:sequence dfdl:separator="{fn:concat('--'),$some_boundary}" 
dfdl:separatorSuppressionPolicy="anyEmpty"  dfdl:terminator="--%CR;%LF;"> 

regards,

Tim Kimber, DFDL Team,
Hursley, UK
Internet:  kimbert at uk.ibm.com
Tel. 01962-816742 
Internal tel. 37246742




From:        "Garriss Jr., James P." <jgarriss at mitre.org> 
To:        "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>, 
Date:        24/06/2013 20:38 
Subject:        [DFDL-WG] Can I concatenate a variable? 
Sent by:        dfdl-wg-bounces at ogf.org 




Suppose I define a variable like this: 
  
<dfdl:defineVariable name="boundary" defaultValue="some_boundary" type=
"xsd:string"/> 
  
Can I later concatenate it with other values?   
  
For example, can I concatenate it as part of a pattern? 
  
<xsd:element name="Preamble" type="xsd:string" dfdl:lengthKind="pattern" 
dfdl:lengthPattern="(.+?)(?=--{$some_boundary})"/> 
  
Can I concatenate it as part of a separator? 
  
<xsd:sequence dfdl:separator="--{$some_boundary}" 
dfdl:separatorSuppressionPolicy="anyEmpty"  dfdl:terminator="--%CR;%LF;"> 
  
TIA!--
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