This property appears in exactly 3 places in the DFDL spec. 

* Section 13.5 where it is defined
* Appendix G: 36.1 Parser - property precedence tables
* Appendix G: 36.2 Unparser - property precedence tables.

The definition in Section 13.5 says 

Indicates whether an xs:decimal element is signed. See 13.6.2 Converting logical numbers to/from text representation and 13.7.1 Converting Logical Numbers to/from Binary to see how this affects the presence of the sign in the data stream. 'yes' means that the xs:decimal element is signed 'no' means that the xs:decimal element is not signed  

Neither Section 13.6.2 nor 13.7.1 mention the decimalSigned property.

We need to add language which clarifies this.

I believe this is roughly what is needed:

In Section 13.6.2, add this material at the start of the section:

The signed number types are byte, short, int, long, integer, float, double
The unsigned number types have names beginning with "unsigned", as well as nonNegativeInteger.
For type xs:decimal the decimal is considered signed if dfdl:decimalSigned="yes" and unsigned if dfdl:decimalSigned="no". 

In Section 13.7.1 we need to add this:

When dfdl:binaryNumberRep="binary", then dfdl:decimalSigned controls whether the underlying representation is interpreted as a twos-complement signed binary integer or an unsigned binary integer. This value is then scaled using dfdl:binaryDecimalVirtualPoint to convert to/from the infoset value. 

When dfdl:binaryNumberRep is 'bcd', no sign is possible and the dfdl:decimalSigned property is ignored. 

When dfdl:binaryNumberRep is 'packed' a sign nibble is required and the dfdl:decimalSigned property is ignored.
(rationale: packed but unsigned is the same as BCD)

When dfdl:binaryNumberRep is "ibm4690Packed" the dfdl:decimalSigned property is used to determine if negative values are allowed, i.e., the packed digits may be preceded by a negative sign nibble.
If dfdl:decimalSigned is "no" then no sign nibble is expected or allowed. 


Mike Beckerle 
Apache Daffodil PMC | daffodil.apache.org
OGF DFDL Workgroup Co-Chair | www.ogf.org/ogf/doku.php/standards/dfdl/dfdl
Owl Cyber Defense | www.owlcyberdefense.com