A typical task along a canon's route

A question to a canon gets one answer. A typical task — a customs dossier for an import, an insurance payout, a measurement uncertainty report — is many questions in the right order, facts from a person between them and a document at the end. The canon’s author knows the order and publishes it next to the package as a task guide (analysis/task-guides.json): which case to pin, which facts to collect and from where, which question cards to ask, where to go on every answer status, and which answers fill which fields of the document.

A guide carries no formula, rate, deadline or threshold: those live in the canon’s .law. It does not choose a disputed reading and does not judge for an authority — a person decides that at a decision step. The engine still executes and proves; the agent and the person only walk the graph and copy answers.

After this page you can take one report from an empty journal to a finished document and say where every value in it came from. The example is the GUM measurement uncertainty report, jcgm.gum/uncertainty-report; it is carried through the whole page.

The report we are building

A measurement result r in microvolts has an estimate of 150 µV and two input quantities, x1 and x2, each entering with sensitivity 1 and uncorrelated. A calibration certificate quotes 12 µV for x1; for x2 only the bounds ±15 µV are known. The person compiling the report chooses a coverage factor k = 2. The identifiers are the ones in the author’s case collection otchet-neopredelennosti that ships with the canon, case KVybranChelovekom (“k chosen by a person”).

The finished document has these values. Each comes from one step of the route; the right-hand column names it.

Section · field	Value	Filled by
Case · result	urn:example:gum:r	pin-case: the person binds the result
Case · date	2026-09-06	the case’s legal time, named in journal new
Case · coverage factor k	2/1	collect-coverage: the person names k
Budget · number of inputs	2	ask-input-count
Budget · u²(xi)	x1: 144/1, x2: 75/1	ask-input-variance, once per input
Budget · contributions	x1: 144/1, x2: 75/1	ask-input-contribution, once per input
Budget · combined uc(y)	15 µV (√219, rounded)	ask-combined
Coverage · degrees of freedom	open: empty collection, not zero	ask-dof
Result · expanded U	30 µV	ask-expanded
Result · U/y	1/5	ask-relative-expanded
Result · level of confidence	about 95 %	ask-level
Result · complete per 7.2.3	TRUE_ONLY	ask-report-complete
Free fields · compiled by, instrument	what the person typed	request-free-fields

These are the values the collection expects; they follow from the GUM formulas, not from a model’s arithmetic. No number in the table is typed by the agent or the person except k and the free fields: every other value is copied from an answer the engine computed and the journal recorded.

Find a guide

From an assistant over MCP, guides are the server’s prompts. prompts/list names them <package>/<guide id>; prompts/get with legal_time and the optional case, locale and step returns the task frame, the pinned packages, a window of the next steps with ready law_ask calls and the uniform template for reading statuses. Getting a prompt executes nothing and accepts no facts. The GUM uncertainty report (jcgm.gum/uncertainty-report) is visible on the public science slice. The profile’s guide catalog is law_packages with catalog: "task-guides".

From a terminal, law guide <package directory> lists guides, law guide <package directory> <id> prints the steps, document sections and boundaries, and --witnesses prints only the commands the author uses to replay their witness paths. In a project with an installed dependency, law guide <dependency name> reads deps/<name>.task-guides.json and checks its bytes against taskGuideCatalogHash in law.lock; a substitution is refused with LDC-E1104. Outside a project, pass the directory.

Two modes

By default a guide is an order hint: the agent asks its cards in its order (law ask … --format brief), follows the handlers of each outcome and copies the status and display fields into its answer. A small measurement on 28 September 2026 showed that this keeps a weaker model from computing a sum itself, while stronger models gain no accuracy from a journal. The journal and the executor are for a document others will check: the result is then law guide journal render --json, whose fields are copied, not asked again.

Walk the report with a journal

The steps below use two shell variables: P is the canon, C the case collection.

Terminal

P=corpus/laws/org/jcgm/gum
C=$P/examples/otchet-neopredelennosti
law guide $P uncertainty-report

The last command prints the 25 steps of the route, the seven document sections and the boundaries. Start a journal on the case and its legal date:

Terminal

law guide journal new $P uncertainty-report --legal-time 2026-09-06 \
  --case KVybranChelovekom --out journal.json

The date of law is named by a person; today’s date is never filled in. It must match the case: a journal opened on another date refuses the case’s answers. The journal pins the guide by the sha256 of the catalog bytes, so a changed catalog refuses new records.

At any point, law guide journal next journal.json prints the next step, the facts the case already holds and a ready command to record it. The records go strictly in route order; a step out of order is refused with the step that was expected.

1. Pin the case and present the facts. The person binds the result and its inputs; a many-valued input is bound as a list:

Terminal

law guide journal add journal.json --step pin-case --bind result=urn:example:gum:r
law guide journal add journal.json --step collect-model \
  --bind input=urn:example:gum:x1 --bind input=urn:example:gum:x2 \
  --present jcgm.gum::input_of --present jcgm.gum::result_estimate …

--present records which facts were presented; what the person does not have is simply not presented. collect-evaluations records the certificate value for x1 and the bounds for x2 the same way.

2. Ask the budget questions. Each ask step is one question to the engine, saved with --out and attached with --answer:

Terminal

law ask $C --case KVybranChelovekom --query-json $C/queries/summarnaya.json --out answers/combined
law guide journal add journal.json --step ask-combined --answer answers/combined

law ask … --out also prints the whole evaluation document; redirect it if you do not need it. A step that asks once per input takes one answer per value: --answer answers/variance-x1 --answer answers/variance-x2. This is where uc = 15 µV enters the journal — as an answer with its own hashes, not as a number someone wrote.

3. Let the outcome choose the branch. ask-dof returns an empty collection: no effective degrees of freedom are derived. The guide moves to ask-dof-infinite, which answers NEITHER — it is not established that all components are exactly known. That outcome sends the route to collect-coverage instead of the table-G.2 path: the person must name k.

4. The person decides. At collect-coverage the person names k and confirms the conditions the canon asks about:

Terminal

law guide journal add journal.json --step collect-coverage --bind coverage-factor=2 \
  --present jcgm.gum::coverage_factor --present jcgm.gum::g66_conditions_hold …

Then come the result questions — U = 30 µV, U/y = 1/5, about 95 %, and TRUE_ONLY for completeness per 7.2.3 — and at request-free-fields the person fills what the canon does not decide:

Terminal

law guide journal add journal.json --step request-free-fields \
  --set "free/compiled-by=…" --set "free/instrument=…"

Other decision steps take --choice selected|declined for a reading, or --choice affirmed|denied|pending for an authority’s answer to a judgment: the guide follows whether the authority has answered, and the canon derives what the answer means.

5. Assemble and check. The seven assemble-* steps take no flags: each section is filled by copying from earlier records.

Terminal

law guide journal check journal.json --replay
law guide journal render journal.json

check --replay re-reads every attached answer and repeats it with law eval; render prints the document from the table above, with every value and the journal entry it came from (--json gives value, display and from for each field).

Reading stops

One template for every canon (see Reading an answer and Silence). In this report:

• an empty collection is not zero: when ask-dof is empty, the field stays open with its reason, and the route continues by its own branch;
• NEITHER is not “no” but the absence of support. Here it sends the route forward to collect-coverage, where the person supplies what the canon cannot derive. Guides that declare a return instead show whyNot and go back to a collect step; if the case has nothing more, that step is passed as it is, and the same answer stops the passage (missing_facts) — the dependent fields stay open;
• when an input has no evaluation, the combined uncertainty comes back empty, the route goes to ask-contribution-count and on to the free fields; the document completes with uc open, not zero;
• several values, or BOTH — none is chosen; the passage stops;
• an incomplete evaluation, a required judgment of an authority or a reading to choose — a stop or a person’s decision step, not a negative answer. A stopped journal records the reason, for example walkthrough stopped at step ask-combined: … — this is not a negative answer.

The journal’s state is open with the next step, completed with the open fields named, or stopped with a reason. “All steps done” means the declared steps were executed, not that the document is legally sufficient.

From code and from an agent

Node: taskGuides, taskGuide and GuideJournal from @arxo/law/task-guides; a case package has pkg.taskGuides(). Python: arxo.task_guides, arxo.GuideJournal. Both facades run the same binary for the journal.

For an assistant there is a separate skill, apply-canon — the companion of formalize-act, which builds canons: it teaches walking a guide, reading statuses by one template and computing nothing.

The agent side of the same walk — steps, branches, human decisions, open fields, and what completion does and does not mean — is Follow a task guide.