DDS — Ref-108 Ownership_interaction_with_deadline

In case where the OWNERSHIP QoS is EXCLUSIVE, the specification
describes that ownership is lost if the DataWriter loses its
liveliness. However it does not describe whether it loses the
ownership if it misses its deadline with regards to writing the
instance.

If this case is left unspecified the most natural interpretations
would be that the DataWriter does indeed maintain ownership even when
it is missing its deadlines. This seems undesirable.

We do not want a DataWriter that has promised to write samples within
a pre-stated deadline and fails that contract to retain ownership of
an instance and by so doing starve prevent other writers from writing
the instance and therefore starve the reader from data. The
underlying goal is to make the system robust to faults that affect a
single entity.

**PROPOSAL**

Modify section 2.1.3.6.2 (EXCLUSIVE kind) to reflect this. This
affects several paragraphs:

• • First paragraph

Replace: The owner is determined by selecting the DataWriter with the
highest value of the strength that is currently "alive" as defined by
the LIVELINESS QoS policy.

With: The owner is determined by selecting the DataWriter with the
highest value of the strength that is both "alive" as defined by the
LIVELINESS QoS policy and has not violated its DEADLINE contract with
regards to the data-instance.

• • First paragraph

After "Ownership can therefore change as a result of (a) ..."

Add a forth case (d) a deadline with regards to the instance that is
missed by the DataWriter that owns the instance.

• • Fifth paragraph

Modify "It is also required that the owner remains the same until
there is a change in strength, liveliness, or a new DataWriter with
higher strength modifies the instance."

To: "It is also required that the owner remains the same until there
is a change in strength or liveliness, the owner misses a deadline on
the instance, or a new DataWriter with higher strength modifies the
instance."

see below