STMML provides a very small number of abstract elements to capture frequently encountered concepts in STM documents. There are no predetermined semantics or ontology; it is expected that descriptive metadata will be added through dictionaries.

All elements can contain any element children and can carry the common STM attributes. Currently there are the following:

• object. Almost anything - concrete, abstract, representable by a noun. Objects can have properties added through scalar, etc.
• action. Represents an action performed during a scientific narrative. It has attributes describing a time-line and conditions so that a procedure could be replayed. It has a container actionList which shares these attributes and which can describe sets of actions.
• observation. Contains narrative or other elements describing an observation, planned or unplanned