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Capitalised Terms have the meaning defined in Table 1. All MPAI-defined Terms are accessible online. Non-capitalised terms have the meaning commonly defined for the context in which they are used or represent an entity in the real world. For instance, Table 1 defines Object, Scene, and User but does not define object, scene, and human.
A dash “-” preceding a Term in Table 1 means the following:
- If the font is normal, the Term in Table 1 without a dash and preceding the one with a dash should be placed before that Term. The notation is used to concentrate in one place all the Terms that are composed of, e.g., the word Data followed by one of the words Format and Type.
- If the font is italic, the Term in the table without a dash and preceding the one with a dash should be placed after that Term. The notation is used to concentrate in one place all the Terms that are composed of, e.g., the word Descriptor preceded by one of the words Face and Body.
Table 1 – Terms and Definitions
| Term | Definition |
| Attitude | |
| – Spatial | Position and Orientation and their velocities and accelerations of a Human and Visual Object in a Virtual Environment. |
| Audio | A Data Type an instance of which represents analogue signals – or is rendered to be perceived – in the human-audible range (16 Hz – 20 kHz). |
| Avatar | An Data Type including the 3D Model of an Avatar and the Face and Body Descriptors. |
| – Model | An inanimate Avatar exposing animation interfaces. |
| – Portable | A Data Type including Avatar ID, Time, Avatar, Language, Speech, Text, Speech Model, Personal Status, Audio-Visual Scene Descriptors, and potentially an input Portable Avatar. |
| Centre Point | The point of an Object selected to have coordinates (0,0,0). |
| Coordinate System | A system where the position of a point is specified by three numbers. |
| – Cartesian | A coordinate system where the three numbers are the signed distances from the point to three mutually perpendicular planes. |
| – Spherical | A coordinate system where the three numbers are: – the radial distance of that point from a fixed origin. – the polar angle measured from a fixed zenith direction. – the azimuthal angle of its orthogonal projection on a reference plane. |
| Data | Information in digital form. |
| – Format | A specific digital representation of Data. |
| – Media | Data representing Text, Speech, Audio, Visual, 3D Model, LiDAR, RADAR, Ultrasound information. |
| – Object | A Data Type including Data of a given Data Type and the Qualifier of that Data Type. |
| – Type | A recognised instance of Data. |
| Descriptor | The Digital Representation of a feature of an Object. |
| – Audio-Visual | A Data Type including the digital representation of the features of an audio-visual instance. |
| – 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. |
| – Visual | A Data Type including the digital representation of the features of a visual instance. |
| 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 – Scenes, Digital Humans etc. – belonging to some levels in a hierarchical classification (taxonomy). |
| Object | A Data Type including Media Data and an optional Qualifier. |
| – 3D Model | A Data Type including 3D Model Data and Qualifier. |
| – Audio | A Data Type including Audio Data and Qualifier. |
| – Audio-Visual | A Data Type including Audio-Visual Data and Qualifier. |
| – Digital | A Digitised or a Virtual Object. |
| – Digitised | Data representing a real object. |
| – Speech | A Data Type including Speech Data and Qualifier. |
| – Text | A Data Type including Text Data and Qualifier. |
| – Visual | A Data Type including Visual Data and Qualifier. |
| 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 Data or a Virtual Space as a human-perceptible entity. |
| Scene | A composition of Objects located according to a Scene Geometry. |
| – 3D Model | A Scene composed of 3D Model Objects. |
| – Audio | A Scene composed of Audio Objects. |
| – Audio-Visual | A Scene composed of Speech and Audio Objects, Visual and 3D Model Objects, and co-located Audio-Visual Objects. |
| – Speech | A Scene composed of Speech Objects. |
| – Visual | A Scene composed of Visual Objects. |
| Scene Descriptors | A Data Type including the Media Objects and their spatial arrangement in a Scene. |
| – 3D Model | A Data Type including a Scene’s 3D Model Objects and Sub-Scenes, and their spatial arrangement. |
| – Audio | A Data Type including an Audio Scene’s Audio Objects and Sub-Scenes, and their spatial arrangement. |
| – Audio-Visual | A Data Type including an Audio Scene’s Speech, Audio, Visual, 3D Model, and Audio-Visual Objects, and their spatial arrangement. |
| – Visual | A Data Type including a Visual Scene’s Visual Objects and Sub-Scenes and their spatial arrangement. |
| Scene Geometry | A Data Type including the spatial arrangement of the Media Objects in a Scene. |
| 3D Model | A Data Type describing the spatial arrangement of the 3D Model Objects and Sub-Scenes in a Scene. |
| – Audio | A Data Type describing the spatial arrangement of the Visual Objects and Sub-Scenes of a Scene. |
| – Audio-Visual | A Data Type describing the spatial arrangement of the Speech, Audio, Visual, 3D Model, and Audio-Visual Objects and Sub-Scenes of a Scene. |
| – Speech | A Data Type describing the Spatial arrangement of the Speech Objects and Sub-Scenes of a Scene. |
| – Visual | A Data Type describing the Spatial arrangement of the Visual Objects and Sub-Scenes of a Scene. |
| Selector | Input Data having the goal to set a parameter (e.g., use of Text vs Speech or Language Preference) or an operating mode of a Machine. |
| Speech | A Data Type an instance of which represents or is rendered to be perceived as human utterances. |
| Text | A series of characters drawn from a finite alphabet of a character set. |
| – Recognised | The Text at the output of an Automatic Speech Recognition AIM. |
| – Refined Text | The Text at the output of a Natural Language Understanding AIM. |
| Virtual Space | A space generated and maintained by a computing platform that can be rendered. |
