Lou's suggestion about <respStmt> being more appropriate (less
tag-abusive) for recording the software used in the creation of markup,
led me to chck P4

<respons> within <respStmt>

<quote>The <respons> element is designed for cases in which fine-grained
information about specific aspects of the markup of a text is desirable
for whatever reason.</quote>

In P4 one of the attributes of <respons> is "desc"

(description) gives a brief prose note supplying any additional
information which should be recorded
 Datatype: CDATA
 Values: any string of characters, typically a phrase or sentence in a
natural language.

Understandably, in P5 <respons> is present without a "desc" attribute.
Could it be given a child element to mirror the function the "desc"
attributed played in P4? In P4 <respons> was an empty element.