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The data values associated with a Topic, passed between applications are known as DDS Samples. A sample represents an atom of data information as returned by a Data Reader’s read/take operations. It consists of two parts; SampleInfo and the Data itself. The Data part is the data as produced by the Publisher. The SampleInfo contains additional information related to the data provided by the data_distribution_service_dds such as a unique key and its associated QoS policies.
Source: OpenSplice Glossary