High Level Format of a When Frame

All structures in the Artwork project, adhere with the following format:

[Structure Name, Structure Filler]

For example,

[Structure Name, Structure Filler]
[sday_week, SDAY_WEEK]
[sday_week, thursday].

The general format of an LTU follows:

LTU = [when-frame, TU*]

Thus, the name of the structure is when-frame and the filler is either zero ([ ]), or more TU.