E.23:4.6 - Cost and BLP discipline

C.19.1 governs the preference for broad, scale-amenable methods when safety, admissibility, and practical fitness are comparable. E.23 uses that preference but does not assume that accepted-work cost is one number. Compare material resources, tools and instruments, adaptation attempts, skilled attention, rework or delay, risk exposure, and avoided loss on their admitted scales. Keep the components separate, reject a dominated option, and use the declared project policy to choose or hold when no option dominates.

Net-cost arithmetic is permitted only after every term has been converted to one declared unit through an admissible conversion whose basis, uncertainty, and scope remain visible. Until then, avoided loss is a separate project estimate rather than a quantity subtracted from concrete burden. A justified avoided loss can still make an expensive loop preferable. For a simple object, a direct edit or adjustment, small repair, lower-cost performer, specialized cycle, or one-shot evaluation can remain the better option.

Choose harness improvement when a named defect in framing, tools, memory, verification or stopping causes avoidable retry and repairing it compares favourably with direct object repair or another available method. Apply C.11.DUA to preparation, recurring use, transition, independent judgement, maintenance and displaced useful work. Leave unavailable cost evidence unknown; a larger harness is not itself a gain.