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Type research: connections and shared meanings

This is the shared reading guide for the six research families in the map. It coordinates vocabulary and ownership; the owning repositories define their formal interfaces and carry their proof evidence.

Six type research families with explicitly conceptual arrows

Read every dashed arrow as a conceptual use or a proposed research task. An arrow does not assert a package dependency, a checked bridge, an equivalence, or a theorem. Residual Evidence Types now has a checked minimal Agda core, two narrow interface comparisons, and a certified finite checker proved to agree with its explorer, described below with proof receipts. Those results do not discharge every obligation represented by an arrow.

What each family means

Family and owner Question and object Boundary

Echo Types

Which possible origins lie over an output after a transformation? Echo f y = Σ (x : A), f x ≡ y retains a witness in the ordinary preimage fibre. The research concerns structured information loss and retained distinctions.

An output need not identify its actual origin. A numeric measure of a residue does not determine the residue’s structure.

Epistemic Types

From which standpoint is a claim available, and with what evidence? E κ A indexes access to a claim by a standpoint; warrants record evidence, and factivity or soundness requires additional structure.

Possessing evidence is not automatically a proof of its claim. Belief, knowledge and a sound warrant have different interfaces.

Tropical Types

How do resource bounds compose? A declared resource algebra supplies operations and laws: max-plus can combine alternatives with max and sequential costs with +; bottleneck paths use a different algebra.

The algebra and cost semantics must be stated. A bound is neither a probability nor the identity of an information residue.

Residual Evidence Types

Which worlds satisfy both an observation and its evidence constraints? Candidate observe r E = Σ (w : W), (observe w ≡ r) × E w. Presence and value identification are questions over all admissible worlds.

The world is not recovered just by constructing a candidate. Real-world soundness also needs the premise that the actual world is admissible. The formal library is work in progress.

Choreographic Types

What happens to retained distinctions, resource bounds and warrants when a global interaction protocol is projected to local participants?

The general K-CUT result is open in the reviewed project description. A causal-order frontier called a cut is not Gentzen cut-elimination; it is also not a statistical causal-identification result.

Secret Types

Which value flows does a confidentiality label permit, and what may a lower-cleared observer learn from an output? A Secret ℓ A classifies a value at a label ℓ; the first model is a two-level Public ⊑ Secret order over a pure, total calculus, targeting termination-insensitive noninterference for public observations.

A label is not cryptography and not an epistemic standpoint: Secret ℓ A does not make a value unreadable, authenticate a principal, enforce runtime access control, or hide timing, storage or network side channels. The baseline declassifies nothing, and no consumer or frontier item is selected for it (2026-10-04); the RMO key-provisioning/disclosure fit is a name-level inference, not a claim.

These are complementary research questions, not successive ranks in a universal hierarchy of type-system strength. They may be expressible using ordinary dependent, refinement, modal or graded constructions. A name alone does not establish a new primitive type or a novelty claim.

Shared glossary

Term Meaning in this guide

Observation

The result of a declared observation function. Keeping only its sign or magnitude changes that function and can merge distinctions.

Fibre / fiber

Origins paired with evidence that the observation function maps them to the specified output. The two spellings mean the same thing.

Candidate world

One world with evidence of observation compatibility and the declared constraints. It is an admissible explanation, not an assertion that this world actually occurred.

Residual

A discrepancy relative to a declared model. In the imported example it is r = u + n. Additivity is an assumption of that example.

Residue

Information retained after a transformation. An Echo residue is not synonymous with a numerical residual or an error term.

Evidence constraint

A predicate restricting candidate worlds. Choosing a bound in an explorer does not establish that real observations obey it.

Standpoint

The agent, observer or evidence state from which a claim is available. It is an explicit index, not necessarily a probability.

Warrant

Evidence for a claim from a standpoint. Soundness needs a separate map from that evidence to the specified claim meaning.

Soundness

A stated guarantee connecting evidence or a successful check to the meaning of a claim, under explicit premises.

Presence

Every admissible world has a nonzero contribution. A meaningful case also requires evidence that at least one world is admissible.

Value identification

The queried contribution has the same value in every admissible world. This does not identify a source or its causal role.

Confounding

A prospective causal specialisation, requiring a causal model and its identification assumptions. An unresolved additive contribution alone does not establish a confounder.

Inconsistency

No candidate satisfies the declared model and constraints. The explorer reports a conflict and issues no presence or identification claim; it does not use an empty candidate set as a useful warrant for every claim.

Resource grade

An element of a declared resource algebra used for compositional usage or cost accounting. Which operations compose which behaviours is explicit.

Echo index

An index of retained information or allowed degradation. It is distinct from a resource grade and from a numerical measure of a residue.

Residue measure

An observation of retained information into a measuring domain. Equal measured values need not mean equal retained information.

What each connection asks us to establish

Connection Conceptual relationship Evidence needed for a stronger claim

Echo → Residual Evidence

Refine the observation fibre with the evidence predicate E.

The first core checks an encoding into Echo.Echo and both round trips. The residual core now also checks dependency-preserving composition and coarsening on its own side (compose-claims, coarsen-claim); whether these laws transport to Echo has not been compared.

Epistemic → Residual Evidence

Make the meaning and evidence obligations of candidate-wide claims explicit.

The first core checks a SoundWarrant for a candidate-wide claim, with an inhabited case and explicit actual-world premises. The residual core now also checks evidence revision and retraction (survives-retraction, revise); their relation to warrant revision in Epistemic has not been compared.

Echo → Choreographic

Track the distinctions retained by projection to participants.

A projection model and correspondence theorem. An informal loss number cannot stand in for the structure of an Echo residue.

Epistemic → Choreographic

Transport warrants with declared standpoint and soundness conditions.

The relevant K-CUT-WARRANT statement and its proof, including its side conditions.

Tropical → Choreographic

Compose bounds for interactions using a stated resource algebra.

A grading semantics and a projection theorem. A result in another proof assistant needs a proved correspondence or a port with its laws re-proved.

The Choreographic README reviewed for this guide uses the phrase "echo loss-grade". The Echo foundation contract explicitly separates Echo indices, residue measures and resource grades. This map preserves that distinction; reconciling the choreographic interface is an open coordination task, not an equivalence asserted here.

Where things belong

  • nextgen-typing: this map, the shared glossary, ownership routing, comparisons and explicitly cross-project integration obligations.

  • residual-evidence-types: the residual model, research plan, explorer, Agda core, and tests or proofs specific to that model.

  • echo-types, epistemic-types, tropical-types, choreographic-types: each family’s definitions, implementations and own proof evidence.

  • secret-types: the confidentiality-label and information-flow specification: its question, boundary, first two-level model and review checklist. It is specification-stage — no Secret type, information-flow calculus, declassification rule or noninterference theorem exists there yet — so this guide asserts no connection obligation for it, and a documentation link is not a mechanised dependency.

  • kategoria: language-development experiments. It is a separate project from the old katagoria repository name, which GitHub now resolves to ideas-to-alphas.

  • typell: verification-kernel implementation; typed-wasm: target and ABI work; panll: the consuming environment. A conceptual connection in this guide does not establish that any family is integrated into these projects.

The machine-readable ownership rules are in placement.a2ml.

First residual milestone: checked, with limits

The first argument is presence without identification. In natural numbers, u+n=2 alone admits both (0,2) and (2,0). Adding n≤1 proves u≠0, but (1,1) and (2,0) still disagree on the value of u. Adding u=0 then makes the constraints inconsistent, so no inhabited case can be built.

The new core also checks ordinary evidence-refined fibre round trips, conditional actual-world soundness, and claim transport under evidence refinement. Three deliberately invalid modules must be rejected by Agda. Both actual sibling interfaces are imported by the comparison modules: Echo’s fibre packaging round-trips, and Epistemic’s SoundWarrant requires explicit actual-world premises.

The proof record lists the theorem names, commands, pinned sibling revisions and standard-library warnings. The hosted Agda proof job passed the core, all three rejection controls and both comparisons on 2026-09-22 for commit 938a7a5764ac18f08b1b7f332378b4d29c32aa37, with the sibling pins at the current echo-types (9c4b72b5) and epistemic-types (dd948fbd) heads, inside a digest-pinned Debian 13 container with Agda 2.6.4.3 and no third-party action. The first receipt, run 34400282291 on 2026-09-09, checked the same core at the original pins. This is newly written work; the separate starter archive mentioned in the imported assessment has not been recovered.

Causal specialisations and probability adapters require their own models and obligations.

Second residual milestone: checked, with limits

The second milestone adds contexts of assumptions with thinnings, dependency-preserving composition and coarsening, constructive evidence revision and retraction, a certified finite checker over the explorer’s signed -6..6 model, and a proved correspondence between that checker and the JavaScript explorer: Correspondence.checker-matches-explorer states Checker.table ≡ ExplorerTable.expected over all 546 configurations and is proved by refl. Nine deliberately invalid modules must now be rejected.

The updated proof record lists the theorem names and boundaries. The hosted proof job passed on 2026-09-30 for commit befdf9641c1bc6ecf58946e5ccbd0c630f4fc4c3: the core, all nine rejections, both comparisons, and the explorer correspondence (bun 1.3.14 verified by SHA-256 and SHA-512, 11 harness tests, byte-for-byte table drift check, and the refl proof), in the same digest-pinned Debian 13 container with Agda 2.6.4.3.

The limit matters: the correspondence certifies the finite checker against the explorer, not the natural-number core against the explorer. The two sibling comparisons still cover the first milestone only; whether composition and revision need an interface beyond Echo.Echo and SoundWarrant is the open question for the next milestone.

Sources and review boundary

Reviewed on 2026-09-09: the local README files for the six type-set projects echo-types, epistemic-types, tropical-types, choreographic-types, kategoria and typell; the imported residual assessment and explorer; and the coordination repository’s placement, architecture and roadmap documents. The residual core and its two direct comparison modules were checked locally and in the linked hosted job with Agda 2.6.4.3 under --safe --without-K. This is a bounded result: the complete constituent proof suites were not rerun, and unrelated local Epistemic work is outside the receipt.

The Secret Types row was added on 2026-10-05 from that repository’s reviewed and merged scope statement (secret-types PR #4, merged 2026-10-04, with the 2026-10-04 owner confirmation and rulings D153 and D154 recorded there). The row registers the family on its stated boundary; it is not an implementation claim. The scope statement itself records that no Secret type, information-flow calculus, declassification rule or noninterference theorem exists yet, that its review checklist has not been completed item by item, and that no consumer or frontier item is selected, so no connection obligation is asserted for it in this guide.

Primary project entry points:

GitHub repository API lookups on that date resolved tropical-resource-typing to tropical-types and katagoria to ideas-to-alphas, while kategoria resolved to its own repository. The historical pipeline documents retain the katagoria spelling; do not silently conflate it with kategoria.

The graphic is a checked-in SVG so it displays in the AsciiDoc README without JavaScript or a diagram service. Its editable source is type-connections.dot. Rebuild it with just type-map (Graphviz required).