B.5.2.1:10 - Worked micro-example: explanatory rivals and a separate next action

Question and case facts. In a constructed service case, O1 is a latency rise above eight concurrent requests, O2 an increase in blocked threads, O3 a higher cache-miss rate, and O4 normal latency in a serial replay. The question is what explains this contrast. These are stipulated teaching inputs, not empirical results about a real service.

Construction. Declare hypothesis grammar v1 with three mechanism flags: lock contention, cache churn and scheduler stalls. The seeds are A, a lock-contention explanation, and B, a cache-churn explanation. NQD-Generate enumerates two declared variations: combine A with B to construct C, an interacting lock/cache explanation; replace A’s mechanism with scheduler stalls to construct D. The finite budget is four hypotheses including the seeds. Provenance records each seed, constructor and resulting claim. The comparison’s must-constraints are that a candidate addresses these service observations using the declared mechanism grammar and makes a discriminating prediction. All four pass after construction.

Coordinates and comparison. Q has two ordered count Scales: predicted observations among O1–O4, maximized, and auxiliary assumptions not established by the case facts, minimized. Prediction coverage is calculated under each candidate’s stated auxiliary assumptions; it is not independent confirmation. A predicts O1/O2/O4 with one unverified lock-scope assumption. The seed cache model B predicts O1/O3 from the stipulated inputs with no additional assumption. C predicts all four using the lock-scope and lock/cache-coupling assumptions. D predicts O1/O4 using unverified scheduler-threshold and recovery assumptions. Their complete comparison is:

The declared DominanceSet is exactly the two Q coordinates, with ε=0. Novelty is Hamming distance on the three Boolean flags to the preceding archive containing A only; it is an integer count from 0 to 3 and stays outside dominance. The descriptor grid has one cell per flag tuple, K=1. Exact duplicate claims are removed; none of these four is a duplicate. D’s scheduler cell is retained under the stated stepping-stone policy even though D is dominated. No D, Surprise or IlluminationSummary reading is needed in this example.

The complete front is {A,B,C}: each trades prediction coverage against auxiliary assumptions. C.18 records that front separately from the retained archive {A,B,C,D}, and its generation record names this NQD-Generate procedure and the seed/operator provenance. No front thinning is applied.

Qualified abductive result. For the present question about blocked threads, B.5.2 compares candidates that explain O2 with at most one unverified auxiliary assumption. A meets that stated plausibility criterion; C needs two, while B and D leave O2 unexplained. A is the qualified prime conjecture, conditional on the lock-scope assumption. Evidence that the blocked threads never wait on that lock would defeat it. Generation and the coordinate counts supply no assurance level or empirical corroboration.

Next-use choice. The separate C.11 question is which available diagnostic action fits a one-hour budget. Reading the existing lock traces takes one hour and addresses A’s open assumption; the combined intervention needed for C takes three hours. Under the declared criterion of addressing the current blocked-thread question within that budget, choose the trace reading and decline C’s intervention for this action. C remains a front member and D remains an archive stepping stone. This choice authorizes no performance beyond its independently applicable permission conditions.