2.1.1213 Part 4 Section 4.6.77, subSp (Subshape)
For additional notes that apply to this portion of the standard, please see the notes for inkTgt, §4.6.47(a).
a. The standard places no restrictions on what the spid attribute refers to.
PowerPoint requires that the spid attribute reference a valid shape that is present both on the current slide and on the diagram referred to by the spid attribute of the parent spTgt element.
b. The standard places no restrictions on the parent spTgt element of the subSp element.
PowerPoint requires that the parent element target a legacy diagram.