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 Sample Info 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