[DFDL-WG] Action 278: Unparser maxOccurs issue

[Mike Beckerle]

I read this over. I agree that current language is not symmetric for
unparsing with parsing, and in this case it should be symmetric. If the
parser is going to stop looking for more instances when maxOccurs is
reached, then the unparser should stop output of those instances when
maxOccurs is reached.

There is a fair amount of complexity to assigning the proper schema
component for use during unparsing, given an infoset, but counting numbers
of occurrences is certainly not the most complex such thing, and parsing
has to do this counting. So unparsing should as well.

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
<http://www.ogf.org/About/abt_policies.php>


On Mon, Jan 19, 2015 at 1:01 PM, Steve Hanson <smh at uk.ibm.com> wrote:

> Please have a position on the below proposal from IBM for this week's WG
> call.
>
> Regards
>
> Steve Hanson
> Architect, *IBM DFDL*
> <http://www.ibm.com/developerworks/library/se-dfdl/index.html>
> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/>
> IBM SWG, Hursley, UK
> *smh at uk.ibm.com* <smh at uk.ibm.com>
> tel:+44-1962-815848
>
>
>
> From:        Steve Hanson/UK/IBM
> To:        DFDL-WG <dfdl-wg at ogf.org>
> Date:        12/01/2015 16:56
> Subject:        Unparser maxOccurs issue
> ------------------------------
>
>
> Possible change to spec needed., where it describes what happens when
> maxOccurs is exceeded during unparsing for occursCountKind 'fixed' and
> 'implicit' (and by implication scalar elements).
>
> It currently says it is a processing error. I think it is better to say
> that the unparser moves on when maxOccurs is reached. This makes the
> behaviour analogous to parsing, when it does not try to parse beyond
> maxOccurs and moves on.  The current unparser wording is based on the
> assumption that any next occurrence of the element in the infoset must be
> an error, but this is not true - the next occurrence could be an occurrence
> of a same named element later in the schema.
>
> An obvious example is:
>
> <xs:element name="data" minOccurs="2"maxOccurs="2"
> dfdl:occursCountKind="fixed" ... />
> <xs:element name="stuff" minOccurs="0" dfdl:occursCountKind="implicit" ...
> />
> <xs:element name="data" maxOccurs="2" maxOccurs="2"
> dfdl:occursCountKind="fixed" ... />
>
> with an infoset where 'stuff' is missing:
>
> message_data
>   data - xx1
>   data - xx2
>   data - yy1
>   data - yy2
>
> A more interesting example is this, taken from MIL-STD-2045 schema (my
> bold comments added):
>
> <xsd:sequence dfdl:separator="">
> *<!-- Element Value1 -->*
>         <xsd:choice>
>           <xsd:sequence dfdl:separator="">
>             <xsd:group ref="FPI_true"/>
>             <xsd:element dfdl:length="4" dfdl:lengthKind="explicit"
> name="Value1" type="xsd:string"/>
>           </xsd:sequence>
>           <xsd:sequence dfdl:separator="">
>             <xsd:group ref="FPI_false"/>
>           </xsd:sequence>
>         </xsd:choice>
> *<!-- Element Value2 -->*
>         <xsd:choice>
>           <xsd:sequence dfdl:separator="">
>             <xsd:group ref="FPI_true"/>
>             <xsd:element dfdl:length="4" dfdl:lengthKind="explicit"
> name="Value2" type="xsd:string"/>
>           </xsd:sequence>
>           <xsd:sequence dfdl:separator="">
>             <xsd:group ref="FPI_false"/>
>           </xsd:sequence>
>         </xsd:choice>
> *<!-- Element Value3 -->*
>         <xsd:choice>
>           <xsd:sequence dfdl:separator="">
>             <xsd:group ref="FPI_true"/>
>             <xsd:element dfdl:length="4" dfdl:lengthKind="explicit"
> name="Value3" type="xsd:string"/>
>           </xsd:sequence>
>           <xsd:sequence dfdl:separator="">
>             <xsd:group ref="FPI_false"/>
>           </xsd:sequence>
>         </xsd:choice>
> </xsd:sequence>
>
> ...where the FPI_true and FPI_false elements are defined in their own
> global groups.
>
>   <xsd:group name="FPI_true">
>     <xsd:sequence dfdl:separator="">
>       <xsd:element default="true" dfdl:length="1"
> dfdl:lengthKind="explicit" dfdl:textBooleanFalseRep="0"
> dfdl:textBooleanTrueRep="1" name="FPI_true" type="xsd:boolean">
>         <xsd:annotation>
>           <xsd:appinfo source="http://www.ogf.org/dfdl/">
>             <dfdl:discriminator>{. eq fn:true()}</dfdl:discriminator>
>           </xsd:appinfo>
>         </xsd:annotation>
>       </xsd:element>
>     </xsd:sequence>
>   </xsd:group>
>
>   <xsd:group name="FPI_false">
>     <xsd:sequence dfdl:separator="">
>       <xsd:element default="false" dfdl:length="1"
> dfdl:lengthKind="explicit" dfdl:textBooleanFalseRep="0"
> dfdl:textBooleanTrueRep="1" name="FPI_false" type="xsd:boolean">
>       </xsd:element>
>     </xsd:sequence>
>   </xsd:group>
>
> If the infoset looked like the following an error would be given, whereas
> it is valid because the second FPI_false is for Value2:
>
> message_prefixedOccurs
>   FPI_false - false
>   FPI_false - false
>   FPI_true - true
>   Value3 - 9999
>
> Regards
>
> Steve Hanson
> Architect, *IBM DFDL*
> <http://www.ibm.com/developerworks/library/se-dfdl/index.html>
> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/>
> IBM SWG, Hursley, UK
> *smh at uk.ibm.com* <smh at uk.ibm.com>
> tel:+44-1962-815848
> Unless stated otherwise above:
> IBM United Kingdom Limited - Registered in England and Wales with number
> 741598.
> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
>
>
> Unless stated otherwise above:
> IBM United Kingdom Limited - Registered in England and Wales with number
> 741598.
> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
>
> --
>   dfdl-wg mailing list
>   dfdl-wg at ogf.org
>   https://www.ogf.org/mailman/listinfo/dfdl-wg
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.ogf.org/pipermail/dfdl-wg/attachments/20150129/074dd4ea/attachment.html>