Elamur Groupantsworld-store-lookup
The groupant beside world/src/store.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.
Facts
Implementation material. A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.
Components
| component | label | where |
|---|---|---|
| approximant | partial | Forward |
| ast | partial | ../syntax.json |
| composition | partial | Composition |
| cost | symbolic unmeasured | Cost |
| descriptant | present | model.md |
| invariant | partial | Invariant |
| tests | bounded evidence | ../model.md#tests |
Obernants
The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.
| id | type | label | where |
|---|---|---|---|
nonbehavior | behavior_complement | partial source derived model | nonbehavior |
antecedents | reverse_reconstruction | partial source derived model | antecedents |
termination | reachability_precondition | partial source derived model | termination |
cache-cost | resource_preimage | partial source derived model | cache-cost |
Parts
Model text
descriptant
Version lookup
Forward
open captures meta, version rows and main. records binary-searches floor(dict bytes/16) entries, reads an exact byte extent, and traverses parent links on miss. text reads positional byte ranges and performs lossy UTF-8 conversion. lemma_file fills sparse indices, treats malformed index as zero and lets later rows overwrite.
Invariant
Nearest explicit match wins, including zero-length records. No sortedness, cycle, metadata-tail or enum-range validation is promised. The selected syntax envelope includes all Store methods; decoder correspondence remains outside the probe.
Cost
Cold dictionary storage and reads are linear in visited dictionary bytes; warm lookup is logarithmic per dictionary plus linear version-parent searches. Each store retains its cache indefinitely.
Epoch memory
2026-10-29: fixed main and meta snapshots coexist with lazy file opens; a handle is not a globally atomic snapshot. Even append-only publication can interleave open's versions read and later main read: captured old rows plus a new delta main can fail inherited-record fallback. That scenario is source-derived and not executed. Successful nearest-match claims require a coherent captured chain; equal ancestor/child payloads are observationally indistinguishable.
Composition
The identity child resolves numeric lemma IDs before comparing the stored projection, while the lexical child projects effective records into feature counts. Record equality is finer than feature equality; unchanged features cannot recover tags or complete words. Parent lookup must preserve inherited ID meanings across child tables. Dense unique canonical tables and representable IDs are explicit conditions. lemma_table_for uses the exact version table or the base table, without an ancestor-table walk. No automatic converse composition or whole-update proof is claimed.
catalog
world-store-lookup: typed model catalog
Domain: finite valid byte files, bounded IDs and successful allocation; an operation's arguments plus its initial filesystem and scheduler state are inputs. Observations include returns/errors and written bytes. No simultaneous writer, path traversal, malformed offsets or crash is assumed unless explicitly modeled. Source-derived conditional relation, not a proof of all Rust executions. Evidence: tests.md distinguishes executed probes from proposed oracles.
Every entry is a separate observation/constraint. Status: partial source-derived conditional model. Subject: world/src/store.rs at SHA-256 6801677c4f17273e615090a790f2e4018387ca5d006aab899bafda09f01b24d9. Reverse operators retain all compatible antecedents; complements are candidate inner bounds, not complements of an empirically fitted forward function. Proposed oracles are not executed evidence.
nonbehavior
Type: behavior_complement.
U is finite sorted well-formed acyclic version stores x lookup outcomes. U minus R includes returning a later ancestor's payload bytes different from the nearer matching payload and latest ignoring a captured nonempty main. Candidate inner bound; payload equality cannot reveal lookup provenance. Probe builds conflicting records.
antecedents
Type: reverse_reconstruction.
For observed records r at (h,i), all chains with nearest matching dictionary entry pointing to r and every earlier dictionary omitting i are compatible. Arbitrary farther ancestors and unrelated IDs remain free. Empty records can be a genuine zero-length entry, not absence. Probe tests zero-length and inherited records.
termination
Type: reachability_precondition.
Miss traversal terminates on absent parent or '-' in a finite acyclic chain. A parent cycle with no match loops; no visited set/depth cap exists. Invalid dictionaries can return wrong misses because sorted IDs are assumed. Probe tests finite miss only; cycles intentionally not run.
cache-cost
Type: resource_preimage.
For V visited versions, cold bytes D and returned L bytes, records costs O(D + sum(log n_v) + V*m + L), m=versions row count due to linear parent search; warm calls avoid D. Cache retains all loaded dictionaries/handles without eviction. Oracle proposed: instrument file opens; no timing claim.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/world/src/store.rs.groupant/lookup.groupant/