# Terms, definitions, and abbreviated terms

For the purpose of this document, the following definitions apply.

## 3.1 Terms and definitions

attribute
  unit of information within an entity, defined by a particular type or reference to a particular entity NOTE There are three kinds of attributes: direct attributes, inverse attributes and derived attributes.
direct attribute
inverse attribute
  unit of information defining queries for obtaining related data and enforcing referential integrity NOTE Similar to the term "navigation property" in entity-relational programming frameworks.
derived attribute
  unit of information computed from other attributes using an expression defined in the schema
constraints on attributes
  data type restricting the values of attributes NOTE The most general constraint is about the existence of attribute values. There are basically two types: mandatory and optional attributes. Values of mandatory attributes must be provided whereas values of optional attributes may be omitted. NOTE For aggregation data types such as Set, List, or Array, the existence constraint is often refined by a minimal and maximal number of elements, which is also known as cardinality.
entity
  class of information defined by common attributes and constraints as defined in [ISO 10303-11] NOTE Similar to the term "class" in common programming languages but describing data structure only (not behavior such as methods).
identification
  capability to find, retrieve, report, change, or delete specific instances without ambiguity
instance
  occurrence of an entity NOTE Similar to the term "instance of a class" in object oriented programming.
object
  anything perceivable or conceivable that has a distinct existence, albeit not material
type
  basic information construct derived from a primitive, an enumeration, or a select of entities NOTE Similar to the "Type" construct as defined in [ISO 10303-11]. NOTE Similar in concept to "typedef" or "value type" in common programming languages.
select
  construct that allows an attribute value to be one of multiple types or entities NOTE Similar to the "Select" construct as defined in [ISO 10303-11]. NOTE Similar to a "marker interface" in common programming languages.
enumeration
  construct that allows an attribute value to be one of multiple predefined values identified by name NOTE Similar to the "Enumeration" construct as defined in [ISO 10303-11]. NOTE Similar in concept to "enum" in common programming languages.
actor
  person, an organization, or person acting on behalf of an organization NOTE A specialization of the general term object.
classifcation
  categorization, the act of distributing things into classes or categories of the same type
constraint
  restriction for a specified reason NOTE A specialization of the general term control.
control
  directive to meet specified requirements such as for scope, time, and/or cost NOTE A specialization of the general term object.
dictionary
  collection of words, terms or concepts, with their definition
element
  tangible physical product that can be described by its shape representation, material representations, and other properties NOTE A specialization of the general term product.
element occurrence
  element's position within the project coordinate system and its containment within the spatial structure
external reference
  link to information outside the data set, with direct relevance to the specific information the link originates from inside the data set
feature
  parametric information and additional property information modifiying the shape representation of an element to which it applies
group
  collection of information that fulfills a specified purpose NOTE A specialization of the general term object.
library
  catalogue, database or holder of data, that is relevant to information in the data set NOTE It is information referenced from an external source that is not copied into the data set.
object occurrence
  characteristics of an object as an individual NOTE Similar to "object", "instance", "individual" in other publications.
object type
  common characteristics shared by multiple object-occurrences NOTE Similar to "class", "template", "type" in other publications.
process
  object-occurrence located in time, indicating "when"
property occurrence
  unit of information providing a value for a property identified by name
property template
  metadata for a property including name, description, and data type NOTE Similar in concept to "extension property" in common programming languages.
property set occurrence
  unit of information containing a set of property occurrences, each having a unique name within the property set
property set template
  set of property templates serving a common purpose and having applicability to objects of a particular entity NOTE Similar in concept to "extension class" in common programming languages.
proxy
  object that does not hold a specific object type information NOTE a specialization of object occurrence.
quantity
  measurement of a scope-based metric, specifically length, area, volume, weight, count, or time
relationship
  unit of information describing an interaction between items
representation
  unit of information describing how an object is displayed, such as physical shape or topology
resource
  entity with limited availability such as materials, labor, or equipment NOTE a specialization of the general term object. NOTE the "resource definition data schemas" section is unrelated to this concept.
space
  area or volume bounded actually or theoretically NOTE a specialization of the general term product.

## 3.2 Abbreviated terms

AEC | Architecture, Engineering, and Construction
AEC-FM | Architecture, Engineering, Construction, and Facilities Management
BIM | Building Information Modeling
GUID | Globally Unique Identifier
IFC | Industry Foundation Classes
IFD | International Framework for Dictionaries
SPF | STEP Physical File
STEP | STandard for the Exchange of Product data
URI | Uniform Resource Identifier
UUID | Universally Unique Identifier

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