ME.25:5.1 - Share preparation while preserving the receiving results

Two engineering analyses use the same fixed set of measurements. Each first converts the source into a common unit and coordinate convention, then derives its own result. Let f be the deterministic conversion, g the first analysis and h the second. The required pair is:

old(x) = (g(f(x)), h(f(x))).

The transformation obtains y=f(x) once and distributes that unchanged value:

new(x) = let y=f(x) in (g(y), h(y)).

The required results agree for every admitted x when the same conversion and input apply and neither consumer changes y. The proposed working rule is to prepare one shared converted dataset for this pair of analyses, identify the input and conversion used, and let both consumers read that result.

Suppose conversion takes 12 minutes, the two analyses take 3 and 5 minutes, and preparing access to the shared result takes 1 minute. Summed effort changes from 12+3+12+5=32 minutes to 12+1+3+5=21 minutes under those assumptions. This is an effort calculation; it does not determine calendar completion when people and tools can work concurrently.

Now change the situation. The second analysis receives corrected measurements. Reusing y from the old input no longer computes h(f(x_new)). The candidate’s reuse rule must identify an unchanged input and conversion, or recompute the affected preparation. The factorization remains correct; its former working precondition has failed.

In another use, the two original preparations were independent measurements rather than repeated deterministic conversion. Sharing one measured value removes that independence. If the measurement errors are independent and each has variance s^2, averaging the two measurements has error variance s^2/2. Copying one measurement twice and averaging it retains variance s^2. The apparent duplication cannot be eliminated under a requirement for the former error variance. MMP.18 recovers the shared dependence; the mathematical function account must be changed before the work is redesigned.