Data Format Description Language (DFDL) v1.0 Specification
OGF Proposed Recommendation GFD-P-R.174, January 31, 2011


21. Optional DFDL Features

The following table lists the features of the DFDL language that are considered optional for DFDL processor implementations.

Feature

Detection

Validation

External switch

Simple type restrictions

xs:simpleType in xsd

Nils

xs:nillable='true' in xsd

Defaults

xs:default or xs:fixed in xsd

Bi-Directional text.

dfdl:textBiDi='yes'

Lengths in Bits

dfdl:alignmentUnits='bits' or dfdl:lengthUnits='bits'

Delimited lengths and representation binary element

dfdl:representation='binary' (or implied binary) and dfdl:lengthKind='delimited'

Regular expressions

dfdl:lengthKind='pattern',

dfdl:assert dfdl:testkind 'pattern' ,

dfdl:discriminator dfdl:testkind 'pattern'

Zoned numbers

dfdl:textNumberRep='zoned'

Packed numbers

dfdl:binaryNumberRep='packed'

Packed calendars

dfdl:binaryCalendarRep='packed'

S/390 floats

dfdl:binaryFloatRep='ibm390Hex'

Unordered sequences

dfdl:sequenceKind='unordered'

Floating elements

dfdl:floating='yes'

dfdl functions in expression language

dfdl:functions in expression

Hidden groups

dfdl:hiddenRef <> ''

Calculated values

dfdl:inputValueCalc <> '' or dfdl:outputValueCalc <> ''

Escape schemes

dfd:defineEscapeScheme in xsd

Extended encodings

Any dfdl:encoding value beyond the core list

Asserts annotations

dfdl:assert in xsd

Discriminators annotations

dfdl:discriminator in xsd

Prefixed lengths

dfdl:lengthKind='prefixed'

Variables

dfdl:defineVariable,

dfdl:newVariableInstances,

dfdl:setVariable

Variables in DFDL expression language

Table 24 Optional DFDL features

 

In order to provide portability of a DFDL schema, a minimal or extended conforming processor must ensure that all the required properties, as defined in the property precedence sections, are present in a schema, even when those properties are not implemented. For example if the bi-directional text feature is not implemented, it is still a schema definition error if dfdl:textBiDi is not set to 'no' an xs:string element.

It is a schema definition error if a DFDL schema uses an optional feature that is not supported by a minimal or extended conforming processor.


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