DDS12 — Clarify PARTITION QoS and its default value

Summary:
In the table in Section 2.1.3, the default partition value is said to be a zero-length sequence, which "is equivalent to a sequence containing a single element consisting of an empty string", which will match any partition. However, if an empty string will match any partition, it is not consistent with normal regular expression matching.

Proposed Resolution:
It is desirable to have the behavior in that if a special partition is specified, it will only match others who have that special partition. If the default behavior is that it will match all partitions, there is no way for a newly created entity to prevent others from matching it, unless the special partition is used.
Therefore, we should not overload the meaning of the empty string to mean matching everything. Instead, the empty string is the default partition. An empty partition sequence or a partition sequence that consists of wildcards only will automatically be assumed to be in the default empty string partition.

Proposed Revised Text:

Section 2.1.3 Supported QoS PARTITION Table
On the "Meaning" Column for the PARTITION QoS;

Replace the following paragraph:

The default value is an empty (zero-length) sequence. This is treated as a special value that matches any partition. And is equivalent to a sequence containing a single element consisting of the empty string.

With

The empty string ("") is considered a valid partition that is matched with other partition names using the same rules of string matching and regular-expression matching used for any other partition name (see Section 2.1.3.13)
The default value for the PARTITION QoS is a zero-length sequence. The zero-length sequence is treated as a special value equivalent to a sequence containing a single element consisting of the empty string.

see above