====== GROUP_DATA QoS Parameter ======
[[ddsf:public:guidebook:06_append:02_quality_of_service:start|return to the Quality of Service (QoS) Parameters ]]

The ''GROUP_DATA'' [[ddsf:public:guidebook:06_append:glossary:q:quality_of_service_qos_policies|QoS]] allows the application to attach additional information to the created ''[[ddsf:public:guidebook:06_append:glossary:p:publisher|Publisher]]'' or ''[[ddsf:public:guidebook:06_append:glossary:s:subscriber|Subscriber]]''. The value of the ''GROUP_DATA'' is available to the application on the ''DataReader'' and ''DataWrite''r entities and is propagated by means of the built-in topics. 

This QoS can be used by an application combination with the ''DataReaderListener'' and ''DataWriterListener'' to implement matching policies similar to those of the ''[[ddsf:public:guidebook:06_append:02_quality_of_service:partition|PARTITION QoS]]'' except the decision can be made based on an application-defined policy.

Source: [[https://www.omg.org/spec/DDS/1.4/PDF | DDS 1.4 Spec]]

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