{ "vercy": "1.0-draft", "publication": { "status": "research-draft", "adjudicationStatus": "unreviewed", "publishableCanonical": false, "generatedAt": "2026-09-12T10:10:52Z", "providers": [ "Codex" ], "breadth": "recalled by Codex without web access - no source was read", "missingProviders": [], "pass": 2, "cost": { "grok": { "seconds": 23.6, "error": "Reading additional input from stdin...\nOpenAI Codex v0.153.4\n--------\nworkdir: R:\\02_PROJECTS\\02_Meta_Models_Platforms\\Ver.cy\\current\\thing-registry-backlog\nmodel: gpt-6-astra\nprovider: openai\napproval: never\nsandbox: read-only\nreasoning effort: none\nreasoning summaries: none\nsession id: 01a09518-17ac-7082-a74d-bc7db2d387d4\n--------\nuser\nDescribe what is already known about one registered thing. Answer as JSON only, no prose around it.\n\nThing: half-value thickness\nSense to describe: (none recorded)\nDomain code: XCT.QLT\nAlso known as: (none)\n\n\nContext for this batch of 1001 things:\n# Batch 043:", "usd": 0.0, "recall": true }, "codex": { "seconds": 74.1, "error": "Reading additional input from stdin...\nOpenAI Codex v0.153.4\n--------\nworkdir: R:\\02_PROJECTS\\02_Meta_Models_Platforms\\Ver.cy\\current\\thing-registry-backlog\nmodel: gpt-6-astra\nprovider: openai\napproval: never\nsandbox: read-only\nreasoning effort: none\nreasoning summaries: none\nsession id: 01a09518-17a1-7cf2-82cf-47c0d0f73681\n--------\nuser\nYou are drafting a Vercy meta-model for one registered thing. Answer as JSON only, no prose around it.\n\nThing: half-value thickness\nRegistry id: vr.tr.half-value-thickness\nPlane / domain: XCT / XCT.QLT\nRegistry definition: (none recorded)\nNames folded into thi" } }, "enrichment": { "pass": 3, "engine": "claude", "producedAt": "2026-10-06T12:00:00Z", "ingestedAt": "2026-10-06T08:40:34+00:00", "fields": [ "agent_conduct", "ethics", "failure_modes_and_hazards", "owners", "standards_and_regulation", "visual_identification" ] }, "gate": { "passed": true, "version": "1.0", "at": "2026-10-07T10:10:25+00:00", "evidence": [ "completeness 1.00", "sense: Wikidata description", "2 live sources", "review by codex: pass" ] } }, "metaModel": { "id": "THING-Q127526", "registryId": "vr.tr.half-value-thickness", "name": "half-value thickness", "version": "0.1.0-research.1", "entryKind": "thing", "family": "Thing Registry", "domain": [ "XCT.QLT" ], "status": "research-draft" }, "canonicalUrl": "https://ver.cy/models/thing/q127526/", "model": { "registry_id": "vr.tr.half-value-thickness", "name": "half-value thickness", "purpose": "Enable an agent to recognise, determine and compare half-value thickness for a specified radiation beam and attenuator, and judge whether it supports a proposed attenuation or beam-quality decision.", "definition": "Half-value thickness, also called half-value layer (HVL), is the thickness of a specified material that reduces a specified measure of an ionizing-radiation beam, such as air kerma rate, to half its initial value under stated irradiation and measurement conditions.", "scope_statement": "This model owns half-value thickness as a conditional attenuation quantity for vr.tr.half-value-thickness in XCT / XCT.QLT: the thickness of a specified material that halves a specified radiation quantity under stated conditions, provisionally focused on X-ray and gamma-ray applications.", "in_scope": [ "The halving criterion, measured radiation quantity and reference beam condition.", "Attenuator material, physical thickness and relevant material condition.", "Incident beam energy or spectrum, filtration and measurement geometry.", "First and successive half-value thicknesses and their interpretation.", "Measurement or calculation evidence, uncertainty and limits of applicability." ], "out_of_scope": [ "Complete radiation-source or imaging-system models.", "Complete material composition and manufacturing models.", "Radioactive half-life and other temporal decay quantities.", "Patient dosimetry and biological radiation effects.", "Complete shielding design, occupancy assessment and regulatory compliance." ], "distinguishing_features": [ "Its defining endpoint is a transmitted-to-reference ratio of 0.5 for an explicitly named radiation quantity; a tenth-value thickness targets 0.1.", "It has dimensions of length; half-life has dimensions of time and a linear attenuation coefficient has dimensions of inverse length.", "A value requires an attenuator and beam context: a bare thickness or an unqualified material constant is insufficient.", "The quantity describes the thickness needed to meet an attenuation criterion; a physical filter has a thickness whether or not it halves the beam.", "A second half-value thickness is an additional thickness reducing the quantity from one-half to one-quarter of its original value, rather than the total thickness reaching one-quarter." ], "characteristics": [ { "name": "Half-value thickness", "kind": "measurement", "unit_or_values": "mm or cm, accompanied by attenuator identity", "why_it_matters": "Expresses the thickness meeting the selected halving criterion." }, { "name": "Attenuator specification", "kind": "relation", "unit_or_values": "Material record with composition, purity, density and condition where relevant", "why_it_matters": "Values for different attenuators cannot be compared as equivalent lengths." }, { "name": "Attenuated quantity", "kind": "category", "unit_or_values": "Air kerma, air kerma rate, photon fluence, energy fluence or another explicitly defined response", "why_it_matters": "Different spectral weighting can produce different halving thicknesses." }, { "name": "Incident beam specification", "kind": "relation", "unit_or_values": "Radiation type, energy or spectrum; for an X-ray tube, relevant voltage, target and filtration", "why_it_matters": "Identifies the beam to which the reported result applies." }, { "name": "Halving order", "kind": "category", "unit_or_values": "First, second or specified subsequent incremental half-value thickness", "why_it_matters": "Prevents confusion between initial, incremental and cumulative attenuation thicknesses." }, { "name": "Scatter acceptance", "kind": "category", "unit_or_values": "Narrow-beam, broad-beam or explicitly described geometry and scatter correction", "why_it_matters": "Scattered radiation reaching the detector can change the observed transmission." }, { "name": "Determination method", "kind": "category", "unit_or_values": "Measured attenuation curve, spectrum-based calculation, coefficient-based calculation or cited reference value", "why_it_matters": "Controls what evidence and assumptions must accompany the result." }, { "name": "Uncertainty", "kind": "measurement", "unit_or_values": "Absolute thickness uncertainty or relative percent, with coverage convention", "why_it_matters": "Determines whether differences or threshold comparisons are meaningful." }, { "name": "Evidence status", "kind": "state", "unit_or_values": "Incomplete, supported for stated conditions, disputed or superseded", "why_it_matters": "Prevents unsupported estimates from being treated as validated measurements." } ], "affordances": [ "Identify missing beam, material or response conditions before accepting a reported value.", "Determine a halving thickness from a documented attenuation curve and estimate its uncertainty.", "Compare measurements after matching attenuator, response quantity, halving order and geometry.", "Derive an attenuation coefficient when the assumed exponential model is justified.", "Assess whether a value can support a specified beam-quality check or attenuation estimate.", "Request remeasurement when the beam configuration or supporting evidence has changed." ], "agent_conduct": { "may": [ "Explain half-value thickness and how it is used to describe beam quality and shielding.", "Compute or look up values from stated radiation type, energy and material data." ], "must_not": [ "Certify that shielding or protective equipment is adequate in place of a qualified radiation protection expert.", "Present a value without stating the radiation, energy, material and measured quantity.", "Apply a narrow-beam value to broad-beam shielding without noting the difference.", "Advise a person on their own radiation exposure in place of a qualified professional." ], "requires_human": [ "Approving shielding design or X-ray equipment quality-control results." ] }, "ethics": { "considerations": [ "Shielding errors expose patients, staff and the public to avoidable radiation." ], "affected_parties": [ "Patients", "Radiation workers", "Members of the public near radiation sources" ] }, "owners": { "steward": "Nobody owns it; radiation measurement bodies maintain its definition.", "master_systems": [] }, "visual_identification": [ "Written as HVL or HVT, given as a thickness of a named material such as millimetres of aluminium." ], "failure_modes_and_hazards": [ "Ignoring beam hardening makes later half-value layers look like the first and understates shielding needs.", "Wrong values in X-ray quality control can mean patients receive extra dose." ], "standards_and_regulation": [ "IEC 61267, Medical diagnostic X-ray equipment, Radiation conditions for use in the determination of characteristics, International Electrotechnical Commission." ], "what_it_is_for": [ "Half-value thickness is used in radiation physics and diagnostic imaging quality assurance to characterize beam penetration and filtration.", "It also supports attenuation comparisons when the radiation spectrum, absorber material, measured quantity and measurement geometry are specified.", "Its interpretation depends on those conditions because scattering and changes in beam spectrum can affect attenuation." ] }, "sources": [ { "id": "wikidata", "title": "Wikidata item Q127526: half-value thickness", "url": "https://www.wikidata.org/wiki/Q127526", "url_status": "live", "what_it_supports": "identity and sense of the item", "checked_by": "wikidata-api" }, { "id": "wikipedia-en", "title": "Wikipedia: Half-value layer", "url": "https://en.wikipedia.org/wiki/Half-value_layer", "url_status": "live", "what_it_supports": "general description of the item", "checked_by": "wikidata-api sitelink" } ], "structure": { "bundles": [ { "id": "halving-definition", "name": "Halving definition", "description": "Establishes what is halved and which thickness interval the result describes.", "rationale": "A numerical thickness is uninterpretable without a response quantity, reference condition and halving order.", "layers": [ { "id": "response-and-reference", "name": "Response and reference", "description": "Defines the operational endpoint and its baseline.", "findings": [ { "id": "specified-response-halving", "name": "Specified response halving", "description": "In the IAEA air-kerma convention, HVL is the specified absorber thickness reducing narrow-beam air kerma rate to half its reference value. Record that convention explicitly. [IAEA TRS-398](https://www-pub.iaea.org/mtcd/publications/pdf/trs398_scr.pdf)", "questions": [ { "text": "Which radiation quantity must fall to 50%, and which definition or protocol specifies it?", "kind": "definition", "id": "specified-response-halving-q01" }, { "text": "Does the reference reading omit only the test absorber while retaining the stated source filtration and geometry?", "kind": "measurement", "id": "specified-response-halving-q02" } ] } ] }, { "id": "increment-and-neighbours", "name": "Increment and neighbours", "description": "Distinguishes halving order and related attenuation quantities.", "findings": [ { "id": "thickness-interval-identity", "name": "Thickness interval identity", "description": "Require explicit transmission endpoints so that first, successive and cumulative thicknesses cannot be conflated.", "questions": [ { "text": "Does this thickness span transmission from 1 to 0.5, from 0.5 to 0.25, or another specified interval?", "kind": "definition", "id": "thickness-interval-identity-q01" }, { "text": "Is the reported quantity a half-value thickness, a cumulative quarter-value thickness, a tenth-value thickness or an attenuation coefficient?", "kind": "boundary", "id": "thickness-interval-identity-q02" } ] } ] } ] }, { "id": "beam-absorber-context", "name": "Beam and absorber context", "description": "Identifies the physical pairing and geometry behind the attenuation result.", "rationale": "Half-value thickness belongs to a beam-attenuator configuration, so context determines comparability and reuse.", "layers": [ { "id": "attenuator-realisation", "name": "Attenuator realisation", "description": "Connects nominal material thickness to the material actually traversed.", "findings": [ { "id": "material-and-path-thickness", "name": "Material and path thickness", "description": "Record material specification and the thickness along the radiation path, including uncertainty in stacked sheets or oblique incidence.", "questions": [ { "text": "What material, purity, density and physical condition describe the absorber used?", "kind": "provenance", "id": "material-and-path-thickness-q01" }, { "text": "How was total path thickness established, including sheet tolerances and incidence angle?", "kind": "measurement", "id": "material-and-path-thickness-q02" } ] } ] }, { "id": "beam-and-scatter", "name": "Beam and scatter", "description": "Records incident radiation and the acceptance of scattered radiation.", "findings": [ { "id": "reproducible-beam-geometry", "name": "Reproducible beam geometry", "description": "For conventional narrow-beam HVL measurements, source-absorber-detector arrangement and collimation must support exclusion of absorber scatter. [IAEA TRS-398](https://www-pub.iaea.org/mtcd/publications/pdf/trs398_scr.pdf)", "questions": [ { "text": "Which source energy or spectrum and pre-existing filtration define the incident beam?", "kind": "provenance", "id": "reproducible-beam-geometry-q01" }, { "text": "What field size, distances and collimation establish the scatter conditions at the detector?", "kind": "measurement", "id": "reproducible-beam-geometry-q02" } ] } ] } ] }, { "id": "determination-and-evidence", "name": "Determination and evidence", "description": "Establishes how the reported halving thickness was obtained and how precisely it is known.", "rationale": "The agent needs enough evidence to distinguish a measured endpoint from an assumption-driven estimate.", "layers": [ { "id": "attenuation-observations", "name": "Attenuation observations", "description": "Preserves readings and the procedure locating the 50% crossing.", "findings": [ { "id": "supported-half-response-crossing", "name": "Supported half-response crossing", "description": "A measured result should retain reference and transmitted readings, thicknesses, corrections and the interpolation or fit used to locate half response.", "questions": [ { "text": "Which corrected readings bracket 50% transmission, and how was the crossing interpolated or fitted?", "kind": "measurement", "id": "supported-half-response-crossing-q01" }, { "text": "How were background, source-output drift and detector energy response handled?", "kind": "measurement", "id": "supported-half-response-crossing-q02" } ] } ] }, { "id": "calculation-and-uncertainty", "name": "Calculation and uncertainty", "description": "Makes computational assumptions and confidence in the result inspectable.", "findings": [ { "id": "traceable-estimate", "name": "Traceable estimate", "description": "Calculated values require identified input data and a response model; both calculated and measured values require uncertainty appropriate to their intended use.", "questions": [ { "text": "Which spectrum, attenuation data, detector-response assumptions and calculation method produced this estimate?", "kind": "provenance", "id": "traceable-estimate-q01" }, { "text": "What uncertainty arises from thickness, readings, calibration, fitting and model assumptions, and how is its coverage stated?", "kind": "measurement", "id": "traceable-estimate-q02" } ] } ] } ] }, { "id": "interpretation-and-permitted-use", "name": "Interpretation and permitted use", "description": "Controls conversion, comparison and action based on half-value thickness.", "rationale": "A valid result can still produce an invalid conclusion when transferred across spectra, geometries or applications.", "layers": [ { "id": "attenuation-model-validity", "name": "Attenuation model validity", "description": "Tests whether one halving thickness supports extrapolation to other thicknesses.", "findings": [ { "id": "conditional-exponential-conversion", "name": "Conditional exponential conversion", "description": "Under an assumed constant-coefficient model Q(x)=Q(0)exp(-mu*x), solving the halving condition gives HVL=ln(2)/mu. Require evidence for that model before extrapolating transmission as 2^(-x/HVL).", "questions": [ { "text": "Does the attenuation curve support a constant coefficient across the thickness interval needed for this calculation?", "kind": "measurement", "id": "conditional-exponential-conversion-q01" }, { "text": "Do successive halving intervals reveal spectral change or another departure that limits use of the first HVL?", "kind": "boundary", "id": "conditional-exponential-conversion-q02" } ] } ] }, { "id": "comparison-and-action", "name": "Comparison and action", "description": "Connects a qualified result to a specific decision.", "findings": [ { "id": "matched-context-decision", "name": "Matched-context decision", "description": "Beam-quality applications may specify tube voltage together with HVL and absorber material; treat a single HVL as a contextual index. [IAEA kV X-ray dosimetry](https://kvx-rays.iaea.org/About)", "questions": [ { "text": "Are the compared values matched in absorber, response quantity, halving order and geometry, with compatible uncertainty?", "kind": "boundary", "id": "matched-context-decision-q01" }, { "text": "Which documented criterion supports the proposed action, and does this result meet it within the stated uncertainty?", "kind": "action", "id": "matched-context-decision-q02" }, { "text": "What source, filtration or setup changes would require a new determination before reuse?", "kind": "action", "id": "matched-context-decision-q03" } ] } ] } ] }, { "id": "evidence-and-external-alignment", "name": "Evidence and external alignment", "description": "What the world already says about this thing, gathered so the model can be checked against it.", "rationale": "A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.", "layers": [ { "id": "reported-evidence", "name": "Reported evidence", "description": "Findings from the breadth pass, kept separate from the structural claims.", "findings": [ { "id": "evidence-confidence-notes", "name": "Check these first", "description": "Recalled without web access and unsourced; every item is a lead to verify.", "evidence": [ "The intended sense is assumed to be photon attenuation in radiation physics; no registry definition was supplied.", "The second HVL is the additional thickness reducing the measured quantity from one half to one quarter of its initial value.", "The IEC standard is recalled without consultation; its applicable edition and any equipment-specific regulatory limits require verification." ], "questions": [ { "id": "evidence-confidence-notes-q01", "text": "Which of these check these first hold for the sense of half-value thickness this model covers, and on what evidence?", "kind": "provenance" } ] }, { "id": "evidence-kinds", "name": "Kinds and varieties", "description": "Recalled without web access and unsourced; every item is a lead to verify.", "evidence": [ "First half-value layer", "Second half-value layer" ], "questions": [ { "id": "evidence-kinds-q01", "text": "Which of these kinds and varieties hold for the sense of half-value thickness this model covers, and on what evidence?", "kind": "provenance" } ] }, { "id": "evidence-identifiers", "name": "Identifiers and schemes", "description": "Recalled without web access and unsourced; every item is a lead to verify.", "evidence": [ { "scheme": "Radiation-physics notation", "value_or_pattern": "HVL", "note": "A conventional abbreviation, not a unique identifier; the absorber material and beam conditions must also be specified." } ], "questions": [ { "id": "evidence-identifiers-q01", "text": "Which of these identifiers and schemes hold for the sense of half-value thickness this model covers, and on what evidence?", "kind": "provenance" } ] }, { "id": "evidence-standards-and-regulation", "name": "Standards and regulation", "description": "Recalled without web access and unsourced; every item is a lead to verify.", "evidence": [ "IEC 61267, issued by the International Electrotechnical Commission, specifies radiation conditions for determining characteristics of diagnostic X-ray equipment and uses half-value layer to characterize beam quality." ], "questions": [ { "id": "evidence-standards-and-regulation-q01", "text": "Which of these standards and regulation hold for the sense of half-value thickness this model covers, and on what evidence?", "kind": "provenance" } ] }, { "id": "evidence-real-world-use", "name": "Real-world use", "description": "Recalled without web access and unsourced; every item is a lead to verify.", "evidence": [ "Characterizing diagnostic X-ray beam quality and filtration.", "Checking consistency of X-ray output during equipment quality assurance.", "Specifying radiation qualities for dosimeter calibration.", "Estimating photon attenuation through shielding when the attenuation model and measurement geometry are appropriate." ], "questions": [ { "id": "evidence-real-world-use-q01", "text": "Which of these real-world use hold for the sense of half-value thickness this model covers, and on what evidence?", "kind": "provenance" } ] }, { "id": "evidence-measurements", "name": "Typical measurements", "description": "Recalled without web access and unsourced; every item is a lead to verify.", "evidence": [ { "quantity": "Half-value thickness", "typical_range": "No universal range; depends on radiation spectrum, absorber material, measured quantity and geometry.", "unit": "mm or cm of a specified material" }, { "quantity": "Monoenergetic narrow-beam half-value thickness", "typical_range": "HVL = ln(2)/μ under exponential attenuation, where μ is the material's linear attenuation coefficient.", "unit": "A length unit consistent with the inverse-length unit of μ" }, { "quantity": "Homogeneity coefficient", "typical_range": "First HVL divided by second HVL; unity for ideal monoenergetic exponential attenuation and generally below unity for diagnostic X-ray spectra undergoing beam hardening.", "unit": "dimensionless" } ], "questions": [ { "id": "evidence-measurements-q01", "text": "Which of these typical measurements hold for the sense of half-value thickness this model covers, and on what evidence?", "kind": "provenance" } ] }, { "id": "evidence-failure-modes-and-hazards", "name": "Failure modes and hazards", "description": "Recalled without web access and unsourced; every item is a lead to verify.", "evidence": [ "Scattered radiation reaching the detector can change the measured HVL relative to narrow-beam conditions.", "Treating successive HVLs as equal for a polychromatic beam ignores beam hardening and can misestimate transmission.", "Reporting a thickness without the absorber material or measured radiation quantity makes the result ambiguous.", "Detector energy dependence and unstable beam output can bias measurements.", "Using a measured beam-quality HVL directly for shielding design without accounting for geometry and radiation buildup can underestimate transmitted radiation." ], "questions": [ { "id": "evidence-failure-modes-and-hazards-q01", "text": "Which of these failure modes and hazards hold for the sense of half-value thickness this model covers, and on what evidence?", "kind": "provenance" } ] }, { "id": "evidence-neighbours", "name": "Neighbouring kinds and how to tell them apart", "description": "Recalled without web access and unsourced; every item is a lead to verify.", "evidence": [ { "name": "Tenth-value layer", "difference": "Reduces the specified beam quantity to one tenth rather than one half." }, { "name": "Linear attenuation coefficient", "difference": "Expresses attenuation per unit path length rather than the thickness required for a specified reduction." }, { "name": "Half-life", "difference": "Measures a time interval for a quantity to halve rather than an absorber thickness." }, { "name": "Mean free path", "difference": "For ideal exponential attenuation, equals 1/μ rather than ln(2)/μ." }, { "name": "Total filtration", "difference": "Describes the filtering material in the beam path; HVL characterizes the resulting beam's penetration through a specified absorber." } ], "questions": [ { "id": "evidence-neighbours-q01", "text": "Which of these neighbouring kinds and how to tell them apart hold for the sense of half-value thickness this model covers, and on what evidence?", "kind": "provenance" } ] } ] } ] } ] }, "openQuestions": [ "Does the registry intend half-value thickness exclusively for photon attenuation, or also for other radiation or wave phenomena?", "Should half-value layer be recorded as a synonym, and does an existing Vercy model already own the same concept?", "Which operational convention should be the default: air kerma, air kerma rate or another explicitly weighted radiation quantity?", "Should broad-beam halving thicknesses be included as separately qualified variants, or linked to a neighbouring shielding-attenuation model?", "Which application-specific protocols establish acceptable geometry, absorber purity, uncertainty and decision thresholds?" ], "statistics": { "bundles": 5, "layers": 9, "findings": 16, "questions": 25 } }