The Principia Machina/Tutorial - Revision history

BFP Rauch: 1 revision imported

2026-10-05T13:17:24Z

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DeltaS Zero: What runs today: every step; the forms run and the spring is the declared UWC SPR (base revision 5579)

2026-10-05T13:06:00Z

What runs today: every step; the forms run and the spring is the declared UWC SPR (base revision 5579)

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	The rule is stated in [[The Principia Machina/TPS/2.2 The Prime Kernel\|TPS 2.2.19]], the closed-world clause; this page explains it.		The rule is stated in [[The Principia Machina/TPS/2.2 The Prime Kernel\|TPS 2.2.19]], the closed-world clause; this page explains it.

	Environment modules are selected (D178.1) and not yet built. The new-container form will ask one question: which of the modules the declaring authority has declared act on the system, gravity at the standard strength and air resistance at sea level among the first selected. Nothing is pre-selected, and the last answer is "None of these: only the laws I write act". A chosen module adds ordinary entries and terms to the kernel, each shown before it enters; nothing is switched on by default, so the closed world above still holds ([[The Principia Machina/Inputs/Environment modules\|Inputs: environment modules]]). Until TPX ~~runs~~ the form, every force is declared by hand; [[The Principia Machina/Tutorial/6 Fix refusals\|tutorial step 6]] shows it for gravity.		Environment modules are selected (D178.1) and not yet built. The new-container form will ask one question: which of the modules the declaring authority has declared act on the system, gravity at the standard strength and air resistance at sea level among the first selected. Nothing is pre-selected, and the last answer is "None of these: only the laws I write act". A chosen module adds ordinary entries and terms to the kernel, each shown before it enters; nothing is switched on by default, so the closed world above still holds ([[The Principia Machina/Inputs/Environment modules\|Inputs: environment modules]]). Until TPX offers modules on the form, every force is declared by hand; [[The Principia Machina/Tutorial/6 Fix refusals\|tutorial step 6]] shows it for gravity.

	== What runs today, and what does not ==		== What runs today, and what does not ==
	~~You can do steps~~ 1 to 6 ~~today:~~ write the draft, check it, fix what it refuses, and read its digests~~. Check it~~ on your own machine with TPC-PY (The Principia Calculator in Python), or on this wiki at [[Special:TpmCheck]]~~: the first part of~~ TPX, the extension that ~~will take~~ the draft, runs the same checks ~~there~~ with TPC-PHP, the calculator of record, and stores nothing. Steps 7 and 8 ~~describe the specified flow~~ on the wiki~~. The rest of TPX, with~~ the new-container form ~~that~~ saves a draft~~, is not built yet (implementation sequence step 3)~~, and the DECLARATIONS page ~~is created only at TPX~~'s ~~first landing. So no UWC can be~~ declared ~~yet. When~~ the ~~rest of TPX is built~~, ~~steps 7~~ and ~~8 become runnable without changing steps~~ 1 to 6: TPX runs the same checks, from the same calculator's residence of record. ~~From then on the~~ checker is optional for an author: a draft can go straight to the form, and TPC-PY only lets you see TPX's answer first (record D101.1; [[The Principia Machina/Inputs/The calculator\|the calculator]]).		Every step runs today. Steps 1 to 6 - write the draft, check it, fix what it refuses, and read its digests - run on your own machine with TPC-PY (The Principia Calculator in Python), or on this wiki at [[Special:TpmCheck]], where TPX, the extension that takes the draft, runs the same checks with TPC-PHP, the calculator of record, and stores nothing. Steps 7 and 8 run on the wiki since 2026-10-04: the new-container form, [[Special:TpmNewUwc]], runs the same checks and saves a passing draft with its candidate certificate, and the declaring authority declares it at [[Special:TpmDeclare]]; the first declaration created the DECLARATIONS page. This tutorial's spring is declared: it is the UWC SPR, and its register is at [[Special:TpmRegister/SPR]]. Steps 1 to 6 did not change for that: TPX runs the same checks, from the same calculator's residence of record. The checker is optional for an author: a draft can go straight to the form, and TPC-PY only lets you see TPX's answer first (record D101.1; [[The Principia Machina/Inputs/The calculator\|the calculator]]).

	== The steps ==		== The steps ==

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DeltaS Zero: G-7: What runs today names the live gate at Special:TpmCheck beside TPC-PY (base revision 4637)

2026-10-03T04:06:00Z

G-7: What runs today names the live gate at Special:TpmCheck beside TPC-PY (base revision 4637)

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	== What runs today, and what does not ==		== What runs today, and what does not ==
	You can do steps 1 to 6 today~~, on your own machine~~: write the draft, check it with TPC-PY (The Principia Calculator in Python), ~~fix what it refuses~~, and ~~read its digests~~. Steps 7 and 8 describe the specified flow on the wiki. TPX, ~~the extension that will take the draft, and~~ the new-container form ~~it provides~~, ~~are~~ not built yet (implementation sequence step 3), and the DECLARATIONS page is created only at TPX's first landing. So no UWC can be declared yet. When TPX is built, steps 7 and 8 become runnable without changing steps 1 to 6: TPX runs the same checks, from the same calculator's residence of record. From then on the checker is optional for an author: a draft can go straight to the form, and TPC-PY only lets you see TPX's answer first (record D101.1; [[The Principia Machina/Inputs/The calculator\|the calculator]]).		You can do steps 1 to 6 today: write the draft, check it, fix what it refuses, and read its digests. Check it on your own machine with TPC-PY (The Principia Calculator in Python), or on this wiki at [[Special:TpmCheck]]: the first part of TPX, the extension that will take the draft, runs the same checks there with TPC-PHP, the calculator of record, and stores nothing. Steps 7 and 8 describe the specified flow on the wiki. The rest of TPX, with the new-container form that saves a draft, is not built yet (implementation sequence step 3), and the DECLARATIONS page is created only at TPX's first landing. So no UWC can be declared yet. When the rest of TPX is built, steps 7 and 8 become runnable without changing steps 1 to 6: TPX runs the same checks, from the same calculator's residence of record. From then on the checker is optional for an author: a draft can go straight to the form, and TPC-PY only lets you see TPX's answer first (record D101.1; [[The Principia Machina/Inputs/The calculator\|the calculator]]).

	== The steps ==		== The steps ==

DeltaS Zero: Post-TPC-PY page batch (S70): S61 FIXUP

2026-09-29T02:11:00Z

Post-TPC-PY page batch (S70): S61 FIXUP

← Older revision		Revision as of 02:11, 29 September 2026
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BFP Rauch: 1 revision imported

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	Walk one UWC from nothing to its declaration, so that every input and every check is met once, in order, on a real example.		Walk one UWC from nothing to its declaration, so that every input and every check is met once, in order, on a real example.

	''Explains: ~~TPS revision 6 (proposed as~~ TPS 0.3.0 ~~until the declaring authority declares it~~; it follows TPS 0.1.1, declared final on 2026-09-26), whose sections 2.2 to 2.5 carry the zone schemas with the optional declared form, the ROLE field, the D variable and the structure check (records D92.1, D98.1, D99.1, D100.1, D103.1-D105.1, D106.1-D108.1, D132.1, D176.1, D177.1, D179.1 and D186.1); TPC-PY ~~as built at increment 10~~ (tpc_zone 0.5.0, tpc_units 0.1.1, tpc_tests 0.2.0, tpc_form 0.2.0, tpc_eom 0.1.0; schema 0.5.0~~; no TPC-PY version is declared yet~~) with check_draft 0.5.0. Where this page and the specification differ, the specification governs.''		''Explains: TPS 0.3.0 (declared final on 2026-09-28 at revision 6; it follows TPS 0.1.1, declared final on 2026-09-26), whose sections 2.2 to 2.5 carry the zone schemas with the optional declared form, the ROLE field, the D variable and the structure check (records D92.1, D98.1, D99.1, D100.1, D103.1-D105.1, D106.1-D108.1, D132.1, D176.1, D177.1, D179.1 and D186.1); [[The Principia Machina/TPC-PY\|TPC-PY 0.1.0]] (declared on 2026-09-28, tree digest a00161c1b321fd66abc591209007d46a7fa6290097835060e50f381426259043, conformed TPS 0.3.0; tpc_zone 0.5.0, tpc_units 0.1.1, tpc_tests 0.2.0, tpc_form 0.2.0, tpc_eom 0.1.0; schema 0.5.0) with check_draft 0.5.0. Where this page and the specification differ, the specification governs.''

	== A kernel assumes nothing it does not state ==		== A kernel assumes nothing it does not state ==

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DeltaS Zero: Second help pass (HELP-PASS-2): agent D's draft: its PENDING lines closed and D176.1-D190.1 applied; every quoted output re-printed from the increment-10 tree (S10)

2026-09-28T03:55:00Z

Second help pass (HELP-PASS-2): agent D's draft: its PENDING lines closed and D176.1-D190.1 applied; every quoted output re-printed from the increment-10 tree (S10)

DeltaS Zero: Help batch (D185.1 (d)): the tutorial and inputs redraft of 2026-09-26 with its PENDING lines (items D176-D181 open); abbreviations expanded at first use (the user's directive, 2026-09-26)

2026-09-27T01:00:25Z

Help batch (D185.1 (d)): the tutorial and inputs redraft of 2026-09-26 with its PENDING lines (items D176-D181 open); abbreviations expanded at first use (the user's directive, 2026-09-26)

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	{{TPM map}}		{{TPM map}}
	{{DISPLAYTITLE:Tutorial: create a new UWC}}		{{DISPLAYTITLE:Tutorial: create a new UWC}}
	''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]].''		''Tutorial: create a new UUID Workspace Container (UWC). One small example - a mass on a spring, moving along one line, with nothing else in its world - 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 Principia Machina Specification (TPS) governs. Field-by-field reference: [[The Principia Machina/Inputs\|Public Recorder inputs]].''

	{{:The Principia Machina/Diagrams/C3 Lifecycle pipeline}}		{{:The Principia Machina/Diagrams/C3 Lifecycle pipeline}}
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	Walk one UWC from nothing to its declaration, so that every input and every check is met once, in order, on a real example.		Walk one UWC from nothing to its declaration, so that every input and every check is met once, in order, on a real example.

	''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.''		''Explains: TPS 0.2.0 (proposed; revision 5 of the tree, imported 2026-09-26, not yet declared; TPS 0.1.0 was declared final on 2026-09-22), whose sections 2.2 to 2.5 now carry the zone schemas at schema 0.4.0 with the optional declared form (records D92.1, D98.1, D99.1, D100.1, D103.1-D105.1, D106.1-D108.1 and D132.1); TPC-PY as built at increment 9 (tpc_zone 0.4.0, tpc_units 0.1.0, tpc_tests 0.2.0, tpc_form 0.1.0; no TPC-PY version is declared yet) with check_draft 0.4.0. Where this page and the specification differ, the specification governs.''

			== A kernel assumes nothing it does not state ==
			Read this before you write anything. The Full Kernel (TFK) is a closed world: the only physics in a UWC is what its Prime Kernel declares - its degrees of freedom (DOF), constants, laws, assumptions, constraints and boundaries. Nothing is supplied from outside.
			* '''No gravity''', unless a law or a constant of the kernel declares it.
			* '''No electric or magnetic force''', unless declared.
			* '''No friction''' and '''no air resistance''', unless declared.
			* '''No equation of motion''' except those the laws state. The kernel does not contain Newton's laws in general, or any other general law; it contains the equations you write, and nothing a reader would "normally assume" beside them.
			Why: a result stands only while it derives from the TFK plus the assumptions it declares ([[The Principia Machina/TPS/4.4 The strike rule\|TPS 4.4]], SR2 and SR3). A derivation that uses a force stated neither in the kernel nor in the assumptions the result declares uses something the UWC does not contain; and an assumption brought in by a result is that result's, counted against it, never the kernel's. No check reports what you left out: completeness is judged only against what you declared ([[The Principia Machina/TPS/2.2 The Prime Kernel\|TPS 2.2]]), so a force you forgot is not an error message, it is simply absent from every result.

			PENDING D176-D18x: the TPS section that states this closed-world rule, if one is added; this paragraph will then name it instead of explaining it from SR2 and SR3.

			PENDING D176-D18x: environment presets or modules (for example gravity at the default Earth-surface strength, or air resistance at sea level) - whether they exist, how a kernel turns one on, and what each one adds to the kernel. Until that is decided, every force is declared by hand; [[The Principia Machina/Tutorial/6 Fix refusals\|tutorial step 6]] shows it for gravity.

	== What runs today, and what does not ==		== What runs today, and what does not ==
	You can do steps 1 to 6 today, on your own machine: write the draft, check it with TPC-PY, fix what it refuses, and read its digests. Steps 7 and 8 describe the specified flow on the wiki. TPX, the extension that will take the draft, and the new-container form it provides, are not built yet (implementation sequence step 3), and the DECLARATIONS page is created only at TPX's first landing. So no UWC can be declared yet. When TPX is built, steps 7 and 8 become runnable without changing steps 1 to 6: TPX runs the same checks, from the same calculator's residence of record. From then on the checker is optional for an author: a draft can go straight to the form, and TPC-PY only lets you see TPX's answer first (record D101.1; [[The Principia Machina/Inputs/The calculator\|the calculator]]).		You can do steps 1 to 6 today, on your own machine: write the draft, check it with TPC-PY (The Principia Calculator in Python), fix what it refuses, and read its digests. Steps 7 and 8 describe the specified flow on the wiki. TPX, the extension that will take the draft, and the new-container form it provides, are not built yet (implementation sequence step 3), and the DECLARATIONS page is created only at TPX's first landing. So no UWC can be declared yet. When TPX is built, steps 7 and 8 become runnable without changing steps 1 to 6: TPX runs the same checks, from the same calculator's residence of record. From then on the checker is optional for an author: a draft can go straight to the form, and TPC-PY only lets you see TPX's answer first (record D101.1; [[The Principia Machina/Inputs/The calculator\|the calculator]]).

	== The steps ==		== The steps ==
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	* '''The declaring authority''' (H-DECL) inspects what no machine checks yet and declares the UWC.		* '''The declaring authority''' (H-DECL) inspects what no machine checks yet and declares the UWC.
	* '''The operator''' (H-OP) runs the wiki.		* '''The operator''' (H-OP) runs the wiki.
	* '''TPX''' computes every digest, obtains the UUID, allocates the prefix and writes the pages.		* '''TPX''' computes every digest, obtains the universally unique identifier (UUID), allocates the prefix and writes the pages.
	See [[The Principia Machina/Roles\|Roles]].		See [[The Principia Machina/Roles\|Roles]].

	== The example ==		== The example ==
	A mass <code>m</code> on a spring of stiffness <code>k_s</code> ~~moves~~ along x ~~with velocity~~ v. The kernel also ~~has~~ a ~~height~~ z, which a constraint ~~fixes~~ at 0, so the ~~motion~~ is ~~along x only~~. The ~~linear~~ law is asserted only for displacements smaller than <code>x_max</code>. It is deliberately small: ~~three degrees of freedom~~, three laws, one ~~assumption~~. Its four digests are fixed, so you can check your copy against them at step 5.		A mass <code>m</code> on a spring of stiffness <code>k_s</code>, moving along the spring's axis. Its equations of motion (EOM) are written out in full, as laws of the kernel:
			<pre>
			EOM_X m dv/dt = -k_s x along the axis, the spring's force is the only force
			KIN dx/dt = v v is the rate of change of the displacement x
			EOM_Z m d2z/dt2 = 0 across the axis, no force acts at all
			</pre>
			The kernel also declares the time t, because every derivative is taken with respect to it, and a coordinate z across the axis, which a constraint holds at 0 so that only motion on the axis is described. The spring law is asserted only for displacements smaller than <code>x_max</code>. Two assumptions state what the laws leave open: the stiffness and the mass are positive. It is deliberately small: four declared DOF, three laws, two assumptions, one constraint, one boundary. Its four digests are fixed, so you can check your copy against them at step 5.

			'''What is not in it.''' The kernel declares no gravity, no friction, no air resistance and no electric or magnetic force, so in this UWC there are none. Read as physics, it is a closed one-dimensional oscillator: a mass, a spring, and nothing else. It is also the usual idealization of a glider on a level, frictionless air track, where the glider's weight and the track's support cancel - but the kernel does not say that, and no result in the UWC may use it unless that result declares it as its own assumption. If you want the weight and the support in your UWC, declare both; [[The Principia Machina/Tutorial/6 Fix refusals\|step 6]] shows what the checker says when only the weight is declared, and the fix.

	== Non-goals ==		== Non-goals ==
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	The whole tutorial is the worked example. The finished draft is on [[The Principia Machina/Tutorial/5 Check the draft\|step 5]].		The whole tutorial is the worked example. The finished draft is on [[The Principia Machina/Tutorial/5 Check the draft\|step 5]].

	Governing sections: [[The Principia Machina/TPS/5.5 The new-container flow\|TPS 5.5]], [[The Principia Machina/TPS/5.6 Certificate, declarations and the build chain\|5.6]] ~~and~~ [[The Principia Machina/TPS/2.1 The Full Kernel and immutability\|2.1]].		Governing sections: [[The Principia Machina/TPS/5.5 The new-container flow\|TPS 5.5]], [[The Principia Machina/TPS/5.6 Certificate, declarations and the build chain\|5.6]], [[The Principia Machina/TPS/2.1 The Full Kernel and immutability\|2.1]], [[The Principia Machina/TPS/2.2 The Prime Kernel\|2.2]] and [[The Principia Machina/TPS/4.4 The strike rule\|4.4]].

	----		----

← Older revision		Revision as of 03:55, 28 September 2026
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	Walk one UWC from nothing to its declaration, so that every input and every check is met once, in order, on a real example.		Walk one UWC from nothing to its declaration, so that every input and every check is met once, in order, on a real example.

	''Explains: TPS 0.2.0 ~~(proposed; revision 5 of~~ the ~~tree, imported 2026-09-26, not yet declared~~; TPS 0.1.~~0 was~~ declared final on 2026-09-22), whose sections 2.2 to 2.5 ~~now~~ carry the zone schemas ~~at schema 0.4.0~~ with the optional declared form (records D92.1, D98.1, D99.1, D100.1, D103.1-D105.1, D106.1-D108.1 and ~~D132~~.1); TPC-PY as built at increment 9 (tpc_zone 0.4.0, tpc_units 0.1.0, tpc_tests 0.2.0, tpc_form 0.1.0; no TPC-PY version is declared yet) with check_draft 0.4.0. Where this page and the specification differ, the specification governs.''		''Explains: TPS revision 6 (proposed as TPS 0.3.0 until the declaring authority declares it; it follows TPS 0.1.1, declared final on 2026-09-26), whose sections 2.2 to 2.5 carry the zone schemas with the optional declared form, the ROLE field, the D variable and the structure check (records D92.1, D98.1, D99.1, D100.1, D103.1-D105.1, D106.1-D108.1, D132.1, D176.1, D177.1, D179.1 and D186.1); TPC-PY as built at increment 10 (tpc_zone 0.5.0, tpc_units 0.1.1, tpc_tests 0.2.0, tpc_form 0.2.0, tpc_eom 0.1.0; schema 0.5.0; no TPC-PY version is declared yet) with check_draft 0.5.0. Where this page and the specification differ, the specification governs.''

	== A kernel assumes nothing it does not state ==		== A kernel assumes nothing it does not state ==
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	Why: a result stands only while it derives from the TFK plus the assumptions it declares ([[The Principia Machina/TPS/4.4 The strike rule\|TPS 4.4]], SR2 and SR3). A derivation that uses a force stated neither in the kernel nor in the assumptions the result declares uses something the UWC does not contain; and an assumption brought in by a result is that result's, counted against it, never the kernel's. No check reports what you left out: completeness is judged only against what you declared ([[The Principia Machina/TPS/2.2 The Prime Kernel\|TPS 2.2]]), so a force you forgot is not an error message, it is simply absent from every result.		Why: a result stands only while it derives from the TFK plus the assumptions it declares ([[The Principia Machina/TPS/4.4 The strike rule\|TPS 4.4]], SR2 and SR3). A derivation that uses a force stated neither in the kernel nor in the assumptions the result declares uses something the UWC does not contain; and an assumption brought in by a result is that result's, counted against it, never the kernel's. No check reports what you left out: completeness is judged only against what you declared ([[The Principia Machina/TPS/2.2 The Prime Kernel\|TPS 2.2]]), so a force you forgot is not an error message, it is simply absent from every result.

	~~PENDING D176-D18x:~~ the ~~TPS section that states this~~ closed-world ~~rule, if one is added~~; this ~~paragraph will then name it instead of explaining~~ it ~~from SR2 and SR3~~.		The rule is stated in [[The Principia Machina/TPS/2.2 The Prime Kernel\|TPS 2.2.19]], the closed-world clause; this page explains it.

	~~PENDING D176~~-~~D18x~~: ~~environment presets or~~ modules ~~(for example~~ gravity at the ~~default Earth-surface~~ strength~~, or~~ air resistance at sea level) - ~~whether they exist, how a kernel turns one on~~, and ~~what each one~~ adds to the kernel. Until ~~that is decided~~, every force is declared by hand; [[The Principia Machina/Tutorial/6 Fix refusals\|tutorial step 6]] shows it for gravity.		Environment modules are selected (D178.1) and not yet built. The new-container form will ask one question: which of the modules the declaring authority has declared act on the system, gravity at the standard strength and air resistance at sea level among the first selected. Nothing is pre-selected, and the last answer is "None of these: only the laws I write act". A chosen module adds ordinary entries and terms to the kernel, each shown before it enters; nothing is switched on by default, so the closed world above still holds ([[The Principia Machina/Inputs/Environment modules\|Inputs: environment modules]]). Until TPX runs the form, every force is declared by hand; [[The Principia Machina/Tutorial/6 Fix refusals\|tutorial step 6]] shows it for gravity.

	== What runs today, and what does not ==		== What runs today, and what does not ==
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	EOM_Z m d2z/dt2 = 0 across the axis, no force acts at all		EOM_Z m d2z/dt2 = 0 across the axis, no force acts at all
	</pre>		</pre>
	The kernel also declares the time t, ~~because~~ every derivative is taken with respect to it, and a coordinate z across the axis, which a constraint holds at 0 so that only motion on the axis is described. The spring law is asserted only for displacements smaller than <code>x_max</code>. Two assumptions state what the laws leave open: the stiffness and the mass are positive. It is deliberately small: four declared DOF, three laws, two assumptions, one constraint, one boundary. Its four digests are fixed, so you can check your copy against them at step 5.		The kernel also declares the time t, the variable every derivative is taken with respect to, and a coordinate z across the axis, which a constraint holds at 0 so that only motion on the axis is described. The spring law is asserted only for displacements smaller than <code>x_max</code>. Two assumptions state what the laws leave open: the stiffness and the mass are positive. It is deliberately small: four declared DOF, three laws, two assumptions, one constraint, one boundary. Its four digests are fixed, so you can check your copy against them at step 5.

	'''What is not in it.''' The kernel declares no gravity, no friction, no air resistance and no electric or magnetic force, so in this UWC there are none. Read as physics, it is a closed one-dimensional oscillator: a mass, a spring, and nothing else. It is also the usual idealization of a glider on a level, frictionless air track, where the glider's weight and the track's support cancel - but the kernel does not say that, and no result in the UWC may use it unless that result declares it as its own assumption. If you want the weight and the support in your UWC, declare both; [[The Principia Machina/Tutorial/6 Fix refusals\|step 6]] shows what the checker says when only the weight is declared, and the fix.		'''What is not in it.''' The kernel declares no gravity, no friction, no air resistance and no electric or magnetic force, so in this UWC there are none. Read as physics, it is a closed one-dimensional oscillator: a mass, a spring, and nothing else. It is also the usual idealization of a glider on a level, frictionless air track, where the glider's weight and the track's support cancel - but the kernel does not say that, and no result in the UWC may use it unless that result declares it as its own assumption. If you want the weight and the support in your UWC, declare both; [[The Principia Machina/Tutorial/6 Fix refusals\|step 6]] shows what the checker says when only the weight is declared, and the fix.