XTCE12 — Usage of readOnly is not clear per documentation

Documentation of readOnly attribute says the following per XTCE 1.1:
A Parameter marked as 'readOnly' true is constant and non-settable

It is not clear if this is intended to include "is constant". Constants should be defined per the dataSource property with a value of "constant" per the dataSource property's documentation.

It is not clear if a readOnly item is settable by any means (even the C2 software itself) or is it just read-only to any clients or external applications.

If it is intended to only influence clients and external applications, the documentation should be updated to be:
A Parameter marked as 'readOnly' true is non-settable

Propose to improve the readOnly attribute annotation to be more clear

We initially attempted to improve the documentation on the readOnly attribute in the ParameterProperties element. This did not quite meet the mark and the improvement was not as clear as it could be.

Propose to modify the current XTCE 1.2 proposal annotation from:

<attribute name="readOnly" type="boolean" use="optional" default="false">
<annotation>
<documentation xml:lang="en">A Parameter marked as 'readOnly' true is constant and non-settable. Note that a slight conceptual overlap exists here between the 'dataSource' and this attribute. When the 'dataSource' is 'constant', then 'readOnly' should be 'true'. Application implementations may choose to implicitly enforce this. Some implementations have both concepts of a Parameter that is settable and a Constant in a different part of the data model.</documentation>
</annotation>
</attribute>

To an update documentation element of:

<attribute name="readOnly" type="boolean" use="optional" default="false">
<annotation>
<documentation xml:lang="en">A Parameter marked as 'readOnly' true is non-settable by users and applications/services that do not represent the data source itself. Note that a slight conceptual overlap exists here between the 'dataSource' attribute and this attribute when the data source is 'constant'. For a constant data source, then 'readOnly' should be 'true'. Application implementations may choose to implicitly enforce this. Some implementations have both concepts of a Parameter that is settable or non-settable and a Constant in different parts of their internal data model.</documentation>
</annotation>
</attribute>