[DFDL-WG] Action 278: Unparser maxOccurs issue
Steve Hanson
smh at uk.ibm.com
Mon Jan 19 13:01:10 EST 2015
Please have a position on the below proposal from IBM for this week's WG
call.
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: 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
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
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
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