918   Use of "ord" to configure enumerated DAI

Created: 11 Sep 2012

Status: Not Applicable

Part: Part 6 (2009-12; Edition 2)

Links:

Page: 99

Clause: 9.5.4.1

Paragraph: Table 45

Category: No impact on this part

Issue

I have to configure the value of an enumerated DAI in SCL.
Should I use the ordinal "ord" (see option A) or the value (see option B) of the enumerated of the DataTypeTemplate section?

Option A:
<DAI name="SIUnit" valKind="Set">
<Val>29</Val>
</DAI>

Option B:
<DAI name="SIUnit" valKind="Set">
<Val>V</Val>
</DAI>

Reading table 45 it can be concluded that enumerated values must be used (not the ordinal "ord").

But the following definition can be found in the scheme ("SCL_DataTypeTemplates.xsd"), which indicates that "ord" identifier must be unique across the enumerated (theoretically value can be repeated):

<xs:element name="EnumType" type="tEnumType" minOccurs="0" maxOccurs="unbounded">
<xs:unique name="uniqueOrdInEnumType">
<xs:selector xpath="scl:EnumVal"/>
<xs:field xpath="@ord"/>
</xs:unique>
</xs:element>

This makes me think that "ord" should be the best option for configuring enumerated DAIs (it must be unique).
Perhaps value should be repeated across the enumerated (options like "unknown", "reserved", "not used", "for future use"... assigned to several "ord"), so using value of enumerated in DAI would be ambiguous.
I am aware that allowing both options shouldn´t be possible to avoid ambiguities (0 can be a valid "ord" and a valid value for an enumerated).
That´s why I think using "ord" to configure enumerated DAIs should be the best option.

Thanks in advance:

Javi.

Proposal