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OpenCDD

This page is a working developer’s reference for the entities you’ll find in any CDD dictionary. Terminology follows IEC 61360-1:2017 and IEC 61360-2:2012; see those publications for the normative text.

Meta-classes

Every entity in a CDD dictionary is an instance of one of a small fixed set of meta-classes. The meta-class determines which attributes the entity carries and how it participates in relationships.

META-CLASS (type definition)MDC_C002 (Class)INSTANCES (entities)AAA001: BatteryAAA002: CablePROPERTIES (characteristics)VoltageCurrentPowerWeightunit: Volt (V)unit: Watt (W)unit: kgis_case_of power-type parents
Code Meta-class Ruby class What it represents
MDC_C002 Class Opencdd::Klass A kind of product (e.g. “fixed capacitor”).
MDC_C003 Property Opencdd::Property A characteristic of a class (e.g. “capacitance”).
MDC_C005 ValueList Opencdd::ValueList An enumerated set of value terms.
MDC_C010 ValueTerm Opencdd::ValueTerm One legal value inside a value list.
MDC_C009 Unit Opencdd::Unit A unit of measure (e.g. “farad”).
MDC_C011 Relation Opencdd::Relation A named association between entities.
EXT_C001 ViewControl Opencdd::ViewControl Visibility / applicability rules.

Every entity, regardless of meta-class, carries the same identifying, semantic, and administrative attribute groups. The meta-class only adds type-specific attributes — Property adds data_type and value_format; Class adds superclass, is_case_of, and applicable_properties.

Identifiers: IRDI and ICID

Every entity is identified by an International Registration Data Identifier (IRDI) — a three-part string with the shape:

<registrant>/<semantic>///<scheme>#<code>

For example:

0112/2///61360_4#AAD009
└─┬─┘  └┬┘   └──┬───┘ └┬──┘
 IEC   TC 3   61360-4   code
  • Registrant (0112) identifies the registration authority (IEC).
  • Semantic (2) identifies the conceptual area.
  • Scheme (61360_4) identifies the dictionary (here, IEC 61360-4).
  • Code (AAD009) is the human-readable identifier inside the dictionary.

The IRDI is the canonical, language-independent handle for the entity. Two systems that cite the same IRDI are guaranteed to be talking about the same dictionary entry.

Attribute groups

Per IEC 61360-1 §21.8, every Item_class carries four attribute groups:

  • Identifying attributes — code, preferred_name, short_name, synonymous_name, definition.
  • Semantic attributes — note, remark, drawing_reference, formula, preferred_letter_symbol.
  • Administrative attributes — version_number, revision_number, status_level, responsible_committee, published_in, published_by.
  • Translation information — per-language variants of preferred_name, definition, note, remark.

The same shape applies (with type-specific extensions) to Property, ValueList, ValueTerm, Unit, and Relation.

Relationships

CDD recognises a small fixed set of structural relationships:

  • Inheritance (superclass) — a Class has exactly one superclass; all applicable_properties are inherited.
  • Is-case-of (is_case_of) — imports a fixed version of another class’s properties without joining its classification tree. See IEC 61360-1 §21.13.
  • Has-a composition — a Property of data type CLASS_INSTANCE_TYPE or CLASS_REFERENCE_TYPE points at another class, building a part-whole tree. See §21.2.
  • Classifying property — a Property whose value list partitions a class into subclasses. See §21.11.

Versioning and status

Every entity has:

  • Version (e.g. 002) — increments when the entity’s semantics change in a way that breaks compatibility.
  • Revision (e.g. 05) — increments for editorial or non-breaking changes.
  • Status level — one of proposal, draft, standard, superseded. See IEC 61360-1 §9.9.
  • Version history — the full chronology of version, revision, status, timestamp, user, and change_request_id for every revision since the entity’s first proposal.

OpenCDD captures and renders the version history per entity so you can see exactly how a definition has evolved.

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