DDS11 — DDS ISSUE# 50] Multiple observers sharing a datareader

Ref-166 Allow_multiple_observers_on_a_datareader

Currently there can only be one "observer" on each DataReader. In
other words, it is not possible to have some independent application
observe the data that a DataReader gets without at the same time
affecting the sample-state and this the behavior of other
data-readers.

It is often the case that debugging tool, an interceptor or some other
utility would like to access the data available on the DataReader
without making its presence noted and thus changing the behavior of
other readers. This is particularly relevant for the built-in topics.

**PROPOSAL**

Add an operation: DataReader:: create_view that returns a
DataReader. This affects 2.2.2.4.1 and the IDL in 2.2.3

This DataReader is a view on the same DataReader so it has the same
QoS and listeners.

The application can use the original DataReader or a view to perform
any operations allowed on a DataReader.

A change of QoS or listener in one view or on the main object affects
the main object and all views.

Read and Take operations act independently on each view. The
application must take the data from all views before it can be removed
from the infrastructure and the resources reclaimed.