View source for The Principia Machina/Tutorial/4 Write the Measure Set

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{{DISPLAYTITLE:Tutorial 4: Write the Measure Set}}
''Tutorial: create a new UWC. One small example - a mass on a linear spring, moving only along x - is taken from a blank file to a declared UWC in eight steps. Each step says what runs today and what is specified but not yet built. It explains; the specification governs. Field-by-field reference: [[The Principia Machina/Inputs|Public Recorder inputs]].''

== Purpose ==
Write the third zone, the last gate: the parameters, the named constants, and a yardstick.

''Explains: TPS 0.1.0, revision 4 (declared final 2026-09-22); the zone schemas the declaring authority selected on 2026-09-22 (records D92.1, D98.1, D99.1, D100.1, and for units D103.1, D104.1, D105.1; schema 0.3.0), whose text enters TPS at revision 5, and the kernel tests and isomorphism checks selected the same day (D106.1, D107.1, D108.1; tpm_kernel_tests 0.2.0), whose text follows at the next TPS revision; TPC-PY as built 2026-09-22 (tpc_zone 0.3.0, tpc_units 0.1.0, tpc_tests 0.1.0; no TPC-PY version is declared yet) with check_draft 0.3.0. Where this page and the specification differ, the specification governs.''

== Step 4.1: the parameters ==
<pre>
"PARAMETERS": {
    "STEP_CONVENTION": "one application of an inference rule or algebraic identity is one step",
    "K": "2",
    "N_X": 2,
    "S_MAX": 10
  }
</pre>

* '''STEP_CONVENTION''': what counts as one derivation step. Say it plainly; every step count in this UWC is read under it.
* '''K''': the multiplier in the test of whether two measured values contradict. A string.
* '''N_X''': how many independent contradictions of a standing record open an audit on it. A whole number, no quotes.
* '''S_MAX''': how deep T3 searches the kernel for a contradiction. A whole number, no quotes.
The example leaves out IC2_POLICY and PROMOTION_FLOOR, so their defaults apply: an untied DOF is a named gap, and a result needs falsifier class F2 to be promoted. Writing the defaults out gives the same digest. The accepted ranges are on [[The Principia Machina/Inputs/Measure Set|Inputs: the Measure Set]].

== Step 4.2: the constants ==
A yardstick uses no literal numbers, so its weights are named here:
<pre>
"CONSTANTS": [
    {"NAME": "w_a", "VALUE": "1"},
    {"NAME": "w_s", "VALUE": "0.5"}
  ]
</pre>

== Step 4.3: a yardstick ==
A yardstick is optional. This one orders records first by whether they contradict the TFK, then by (assumptions + 0.5 x steps), then by steps:
<pre>
"YARDSTICKS": [
    {
      "NAME": "combined_distance",
      "KEY": ["SR1", "WSUM:w_a*A;w_s*S", "S"],
      "LIMITING": []
    }
  ]
</pre>

It meets the key rules: it begins with SR1, its weights are named constants, and one more assumption never makes a record closer. See [[The Principia Machina/Inputs/Yardsticks|Inputs: yardsticks]].

== Step 4.4: check ==
Add <code>"TMS": { ... }</code> and run the checker. With all three zones present it now runs every check, runs the yardstick on the synthetic record suite, runs the final pass, and prints the digests; the output is on the next page.

== Non-goals ==
The values here are illustrative. Choose yours under the strike rule ([[The Principia Machina/TPS/4.4 The strike rule|TPS 4.4]]). The project-wide parameters in [[The Principia Machina/TPS/7.2 Declared parameters|TPS 7.2]] are not part of any Measure Set.

== Worked example ==
The step is its own example.

Governing sections: [[The Principia Machina/TPS/2.4 The Measure Set|TPS 2.4]], [[The Principia Machina/TPS/4.4 The strike rule|4.4]] and [[The Principia Machina/TPS/4.5 TMS compliance|4.5]].

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Previous: [[The Principia Machina/Tutorial/3 Write the Translation Manifold|3 Write the Translation Manifold]]. Next: [[The Principia Machina/Tutorial/5 Check the draft|5 Check the draft]].

[[Category:The Principia Machina]]