Add demand and proposed workplan for Attribute Value Type catalog.

Consumer citation-evidence needs closed value types; ITC-DATA has Attribute
and DataType stubs but no catalog. Track as ITC-WP-0013.

demand/AttributeValueTypes.md

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+# Demand: Attribute Value Type Catalog
+
+**Status:** inbound demand (un-reviewed)  
+**Date:** 2026-07-30  
+**Source:** citation-evidence Capture UX (consumer)  
+**Related consumer draft:** `citation-evidence/wiki/AttributeValueTypes-proposal.md`  
+**Proposed workplan:** ITC-WP-0013
+
+---
+
+## Demand signal
+
+Consumer **citation-evidence** needs a **closed, versioned catalog of
+attribute value types** for evidence-backed structured capture (key / type /
+value), including:
+
+- `time`, `datetime`
+- `amount` (quantity + currency)
+- `one-of` (single selection from a code list)
+- `some-of` (multi selection from a code list)
+
+plus existing scalars `text`, long text, `date`.
+
+The consumer must not invent a permanent private type system if InfoTechCanon
+is the semantic reference layer for info-tech domains.
+
+---
+
+## Gap vs current canon
+
+`InfoTechCanonDataModel` already defines:
+
+- Attribute, Field, DataElement, Representation, DataType, CodeList, Constraint
+
+But:
+
+- **DataType** is only a one-line stub,
+- **Representation** lists open examples without a closed catalog,
+- there is **no** machine-readable AttributeValueType registry for application
+  forms / capture UIs.
+
+This demand is for a **canonical collection of value types** (and encoding
+rules), not for a new domain entity competing with Attribute/Field.
+
+---
+
+## Proposed placement
+
+**Preferred:** extension or section under **ITC-DATA** (Data Model):
+
+- concept: `AttributeValueType` (or closed `Representation` profile for
+  capture/forms)
+- artifact: markdown standard + YAML catalog under `infospace/`
+- relationships: AttributeValueType → CodeList (for one-of/some-of), → Constraint
+
+**Avoid:** scattering type ids only inside citation-evidence.
+
+---
+
+## Success criteria
+
+1. Closed list of type ids with definitions and wire encodings.
+2. Clear mapping to Representation / CodeList / Constraint.
+3. Consumer citation-evidence can depend on the catalog (copy or generated
+   constants) without forking names.
+4. Processed via Purpose/Demand if required by ITC-WP-0006 before kernel edit.
+
+---
+
+## Non-goals
+
+- Full statistical data type system.
+- UI widget standards (consumer concern).
+- Vendor form-builder schemas (SurveyJS, etc.) as canon.