Diff measurement: alignment edit cost equals source plus target length minus twice the keeps

What this target establishes

Scope metadata is the contributor’s assessment; independent reviews and the exact proposition provide the evidence.

Obligations

cost accounting

Cost metric

edit count

Model

Keep/delete/insert alignment: cost + twice the keeps equals source length plus target length.

Assumptions

Keep costs zero; insertion and deletion each cost one.

Implementation correspondence

abstract model

Limitations

Accounting only; no minimality, substitutions, encoded-byte cost or runtime guarantee.