Terms beginning with a capital letter have the meaning defined in Table 1. Terms beginning with a small letter have the meaning commonly defined for the context in which they are used. For instance, Table 1 defines Object and Scene but does not define object and scene. Words beginning with a small letter may also refer to an entity in the real world as opposed to a Virtual Environment.

A dash “-” preceding a Term in Table 1 indicates the following readings according to the font:

  1. Normal font: the Term in the table without a dash and preceding the one with a dash should be read before that Term. For example, “Avatar” and “- Model” will yield “Avatar Model.”
  2. Italic font: the Term in the table without a dash and preceding the one with a dash should be read after that Term. For example, “Avatar” and “- Portable” will yield “Portable Avatar.”

The full collection of MPAI Term definitions is available online.

Table 1 – General MPAI-HMC terms

Term Definition
Audio Digital representation of an analogue audio signal sampled at a frequency between 8-192 kHz with a number of bits/sample between 8 and 32, and non-linear and linear quantisation. Data with characteristics of Audio may be synthetically produced.
Avatar An Object rendered to represent a Human of a Machine in a virtual space.
–          Model An inanimate Avatar exposing animation interfaces.
–          Portable A Data Type including Avatar ID, Time, Audio-VisualScene Descriptors, Spatial Attitude, Avatar Model, Body Descriptors, Face Descriptors, Language Preference, Speech Coding, Speech Data, Text, and Personal Status [5].
Centre Point The point of an Object selected to have coordinates (0,0,0).
Context Additional information about a communication emitted by an Entity, such as language, culture etc..
Data Information in digital form.
–          Format The standard digital representation of Data.
–          Type An instance of Data with a specific Data Format.
Descriptor The Digital Representation of a feature of an Object.
–          Body A Data Type including the digital representation of the features of the body of a real or digital human.
–          Face A Data Type including the digital representation of a feature of the face of a real or digital human.
Digital Representation Data corresponding to and representing a physical entity.
Environment A Virtual Space that may be null or may include an Audio-Visual Scene.
Human A human being in a real space.
–          Digital A Digitised or a Virtual Human.
–          Digitised An Object that has the appearance of a specific human when rendered.
–          Virtual An Object created by a computer that has a human appearance when rendered but is not a Digitised Human.
Identifier The label uniquely associated with a human or an Object.
Instance An element of a set of entities – Objects, Digital Humans etc. – belonging to some levels in a hierarchical classification (taxonomy).
–          Audio The instance of an Audio Object.
–          Visual The instance of a Visual Object.
Object A data structure that can be rendered to cause an Experience.
–          Audio An Object described by Audio Descriptors.
–          Audio-Visual An Object described by Audio-Visual Descriptors.
–          Body A digital representation of the body of a Human or a Machine.
–          Descriptor The digital representation of the feature of an Object.
–          Digital A Digitised or a Virtual Object.
–          Digitised The digital representation of a real object.
–          Face The digital representation of the face of a Human or a Machine.
–          Speech An Object described by Speech Descriptors.
–          Text A string of Text.
–          Virtual An Object not representing an object in the real environment.
–          Visual An Object described by Visual Descriptors.
Orientation The 3 Euler angles of an Object in a Virtual Space.
Position The coordinates of a representative point for an object in a Virtual Space with respect to a set of coordinate axes.
Rendering The process of instantiating a Virtual Space as a human-perceptible entity.
Scene A composition of Objects located according to a Scene Geometry.
–          Audio A Scene composed of Audio Objects.
–          Digital A digitised scene or a Virtual Scene
–          Audio-Visual A Scene composed of Audio Objects, Visual Objects and co-located Audio-Visual Objects.
–          Visual A Scene composed of Visual Objects.
Scene Descriptors The digital representation of a feature of a scene.
–          Audio A Data Type including the digital representation of the audio features of a digital scene.
–          Audio-Visual A Data Type combining the Audio or Visual Scene Descriptors.
–          Visual A Data Type including the digital representation of the visual features of a digital scene.
Scene Geometry The digital representation of the Object arrangement of a Scene.
–          Audio A Data Type describing the Spatial arrangement of the Visual Objects of a Scene.
–          Audio-Visual A Data Type describing the Spatial arrangement of the Audio, Visual, and Audio-Visual Objects of a Scene.
–          Visual A Data Type describing the Spatial arrangement of the Visual Objects of a Scene.
Attitude
–          Spatial Position and Orientation and their velocities and accelerations of a Human and Visual Object in a Virtual Environment.
Virtual Space A space generated and maintained by a computing platform that can be rendered.
Speech Digital representation of analogue speech sampled at a frequency between 8 kHz and 96 kHz with a number of bits/sample of 8, 16 or 24, and non-linear and linear quantisation or compressed. Data with characteristics of Speech may be synthetically produced.