#A.19.SOURCE-SET-SPACE-SUBSTRATE:0.2 - What this buys

Preface node heading:a-19-source-set-space-substrate-0-2-what-this-buys:24323

#What this page is

This is generated FPF reference text from the specification preface or supporting sections. It helps interpret FPF; it is not FPF Reference product documentation.

#Methodology

Use it to understand how the specification wants to be read, then return to a route, pattern, or work packet for active work. Cite generated IDs only when the wording changes the task decision.

#Content

This pattern buys one conservative but expressive substrate declaration:

• the active source set stays visible;
• the search-side and outcome-side references over A.19 spaces stay distinct;
• the relation between those refs becomes inspectable instead of being hidden in one overloaded noun or verb;
• heavier qualifier refs remain available without being forced into every case;
• and interpretive-view or publication neighbors can reuse the substrate without changing what it means.

The practical payoff is simple: readers can tell what the line is acting on, what relation between the two space refs it assumes, what kind of qualification they must keep in view, and which neighboring pattern governs the next move if that requirement grows.

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Last Updated: 2026-06-17 — upstream FPF commit 646b0b9b (github.com/ailev/FPF)