The rule makes it possible for a DFDL processor to identify which member it is parsing merely by counting separators. Without this rule, every position in a delimited group would be a point of uncertainty ( well, every position after the first variable-occurrence member of the group ).

In your example, the variable-occurrence element is the final member of the group. The working group did discuss making an exception for this case, but we decided to keep the rule simple because this workaround exists:

     <xsd:element name="ContentType" dfdl:initiator="Content-Type:%SP;" dfdl:terminator="%CR;%LF;">
       <xsd:complexType>
           <xsd:sequence dfdl:separator=";" dfdl:separatorSuppressionPolicy="Never">
               <xsd:element name="MimeType" type="xsd:string"/>
               <xsd:sequence dfdl:separator=";" dfdl:separatorSuppressionPolicy="SuppressedAtEndLax">
                   <xsd:element name="Parameter" type="ParameterType" minOccurs="0" maxOccurs="unbounded" dfdl:occursCountKind="implicit"/>
               </xsd:sequence>
           </xsd:sequence>
       </xsd:complexType>
   </xsd:element>

regards,

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




From:        "Garriss Jr., James P." <jgarriss@mitre.org>
To:        "dfdl-wg@ogf.org" <dfdl-wg@ogf.org>,
Date:        18/07/2013 17:19
Subject:        [DFDL-WG] Why do occursCountKind=implicit and separatorSuppressionPolicy=never collide with unbounded?
Sent by:        dfdl-wg-bounces@ogf.org

---

The Content Type header can have multiple parameters, like so:
 
Content-Type: text/plain; charset=UTF-8; name=file.txt
 
I have defined the Content Type like so in DFDL:
 
    <xsd:element name="ContentType" dfdl:initiator="Content-Type:%SP;" dfdl:terminator="%CR;%LF;">
       <xsd:complexType>
           <xsd:sequence dfdl:separator=";">
               <xsd:element name="MimeType" type="xsd:string"/>
               <xsd:element name="Parameter" type="ParameterType" minOccurs="0" maxOccurs="unbounded" dfdl:occursCountKind="implicit"/>
           </xsd:sequence>
       </xsd:complexType>
   </xsd:element>
 
When I run this against a Content Type with 0 or 1 parameters, everything is good.  But when I run it with a Content Type header with two parameters, Daffodil throws this error:
 
2013-07-18 12:10:13:856  edu.illinois.ncsa.daffodil.compiler.ProcessorFactory Error[Schema Definition Error: separatorSuppressionPolicy='never' with occursCountKind='implicit' required bounded maxOccurs.
Schema context: element.Parameter. Location line 23 column 180 in
 
It seems that an element can’t have separatorSuppressionPolicy='never' and occursCountKind='implicit' if it’s unbounded.  
 
Why is this an issue?

TIA
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