NOT.5:4.6 - Establish the return that the work requires

For an unchanged round trip, translate and reconstruct the source at the required level: the same expression, the same interpreted structure or the same needed consequence. State which level is obtained. Recovering a directed graph up to layout does not recover where its boxes were drawn.

For a target edit, construct a backward update using the edited target and retained source information. Specify what remains fixed and what may change. In the ordinary single-view setting, check two properties: returning an unchanged view leaves the source unchanged; translating the updated source yields the requested view. These properties still leave a choice of update policy, worked in :5.3. They do not mean that all possible edits must be accepted.

When several views constrain a shared source, distinguish the user’s changed requirement from values merely copied from the earlier view. NOT.6 handles their propagation and possible conflict. An unchanged value in a submitted view is not necessarily an instruction to freeze it.

If conversion performs effects such as asking a reader for missing information or changing external state, include the relevant behavior in the return claim. Recovering the same output value need not undo those effects. CMP.12 supplies the computational correspondence when an executable implementation is required.

Stop once the chosen operation and required return work within their stated conditions. Retain the translation rule, any supplement and the loss that changes later use where the recipient can find them. Reopen the affected construction when the receiving question, source interpretation or admitted edits change.