Composite and Combined Controls, Virtual Condition, and Drawing Interpretation
Stacked frames and hard boundaries
Composite position uses a single geometric symbol with stacked segments. The upper segment locates the pattern to all the datums; lower segments control the internal location, that is feature-to-feature spacing, and orientation of the pattern, and may drop the locating datums. A lower segment's tolerance must be smaller than the segment above, and its datum references must be a subset in the same order. Do not confuse a composite frame with multiple single-segment frames: there, each frame carries its own symbol and is an independent, complete requirement.
Virtual condition is the worst-case boundary produced by the combined effect of size and geometric tolerance: for an external feature, MMC plus geometric tolerance; for an internal feature, MMC minus geometric tolerance. It defines the boundary that a functional gauge or mating part must clear, and it drives gauge design and clearance analysis. Bonus tolerance exists precisely because the actual feature departs from MMC while the virtual-condition boundary stays fixed.
Interpretation questions reward systematic reading: find the basic dimensions locating every toleranced feature, confirm each datum is functional and reachable, check that modifiers are legal, and verify the zones nest sensibly - form tighter than orientation, orientation tighter than location.
Rule of thumb: compute the virtual condition for every feature of size before answering anything else; it converts a page of symbols into a set of hard boundaries you can reason about.