A subject is an individual participant for whom motion capture data exists within the library. See the Visual3D wiki for its perspective on analyzing multisubject data.

Subjects can be identified in one of two ways: by a particular prefix and by a set of subject tags.

A subject prefix is a set of characters, like “S001” or “S002”, that is prepended to the beginning of signal names in order to distinguish between two signals with the same anatomical meaning for different subjects within a single .c3d file. Adding this subject prefix ensures that, for example, if the signal AnkleMoment_X exists for two subjects within a single .c3d file then the signal names “S001:AnkleMoment_X” and “S002:AnkleMoment_X” are unambiguous for both Sift and the human user.

A subject tag is a generic name that can be associated with a subject in the way that file tags can be used to group files with particular characteristics. For example, within a single study there could be many subjects with the Pitcher tag and many subjects with the Batter tag. Or, there could be many Ball-carrier subjects and many Tackler subjects.

If Sift detects that your library contains multi-subject data (via the presence of subject prefixes and tags) then you will be able to use these in your query definitions. In addition to the subject tags found in the library, you can also use the “meta-tags” NO_SUBJECT or ALL_SUBJECTS to define which signals you want your query to return.

Auto-building groups will append the subject tag used to the end of the group name within the Explore Page . Workspaces in the Queried Data widget will have the relevant subject prefix appended as well.