Safe reuse when configurations change

This overview explains how Boolean feature constraints and their identities change across model revisions. A familiar model name does not guarantee that a cached result remains valid after a constraint changes. Let P mean the premium option is selected and B mean its base option is selected. Version one requires premium to imply base. A configuration can omit premium, but selecting premium without base violates this rule. With premium and base both selected, implication is true. With premium selected and base absent, implication is false. We have evaluated complete selections under a specified version instead of treating a product label as a self-explanatory condition. Version two adds a resource requirement for premium. The complete rule has changed. An earlier satisfying selection must be checked under this revised conjunction before it is accepted as current. Features form Boolean choices constrained by requires and excludes rules. Reusing an artifact across revisions needs exact source and assumption identity, not just a familiar model name. Use Core, Cloud, Local, Analytics and Export. Require Core. Cloud and Local exclude each other; Analytics requires Cloud; Export requires Analytics. With Core, Cloud and Analytics true, Local and Export false, the selection is valid. In revision two, add Export requires Local. A selection enabling Export now conflicts with the Cloud requirement inherited through Analytics. Export now requires Local, but it also requires Cloud through Analytics. Cloud and Local exclude each other. This is a conceptual revision example, not a deployed product benchmark. Retained feature-model lifecycle work keeps cold, warm and reload costs separate and does not justify a universal CM default. A validity bit, full count and distinct projected feature count remain different queries. Return to the opening premium, base and resource model. Here P means premium, B means base, and R means resource. Its version two requires both P implies B and P implies R. This is separate from the other product model. Set P, B and R all to one. Premium now has both the base and resource requirements available. Each implication returns one, and their conjunction returns one. This revised rule is not a blanket rejection of premium configurations; it rejects only selections that violate at least one required clause. This case establishes a specific contrast. The revised policy accepts this selection. Recompute decisions under the current version. Keep the input, intermediate values, and conclusion together when comparing it with the previous case. The calculated answer belongs to this complete assignment under the stated rule. Take premium and base selected but resource absent. Version one only checked premium's dependence on base, so it accepted this selection. That old result is correct for the old rule. The new implication fails because premium is selected while the required resource is absent. Combining the old successful clause with this zero gives zero. The selection is rejected under version two. The old final decision cannot stand in for the new one. That does not require discarding every compatible unchanged subexpression. Track the full rule version and the dependencies of each reusable artifact so that valid reuse is distinguished from a stale answer. Revalidate or invalidate dependent artifacts after a revision. Keep validity, full-assignment counts, and projected feature counts distinct.