It is a publicly available specification from the Object Management Group (OMG).
SMM specifies a metamodel for defining, representing and exchanging both measures and measurement information related to any structured information model, such as the OMG Meta Object Facility (MOF™) standard, defining an XMI interchange format between metric extraction tools.
SMM defines representations for: The process of extracting metrics, requires a SMM tool to apply the measures to an observation scope that hold one or more models.
Whenever a measurement graph is produced, it is associated to an observation that is dated and tagged with information describing the tool used to extract the metrics.
Observations exist to be passed to metric reporting tools that can provide additional features like visualization and statistical control.