1     Definition 2     Functional Requirements 3     Syntax
4     Semantics 5    Conformance Testing 6     Performance Assessment

1      Definition

A Data Type that conveys information about position, orientation, or spatial relationships within a defined reference frame.

2      Functional Requirements

  1. Cue Identification: Must include a unique identifier or type (CueType) to classify the nature of the cue (e.g., absolute, relative, keyword, region, range).
  2. Reference Frame Support: Must support multiple frames of reference:
    • World (absolute coordinates)
    • Entity/Device (relative to user or device)
    • Object-based (relative to a specific object)
  3. Location Specification: Must allow:
    • Absolute positioning via LocationRef or coordinates.
    • Relative positioning via expressions (e.g., +2m x, ahead 3m).
    • Semantic positioning via keywords (e.g., near, inside).
  4. Region Definition 
    • Must support geometric region specification:
      • Shapes: sphere, box, cylinder, mesh, mask.
      • Parameters: centre, size, orientation, etc.
    • Must enforce validation of region parameters (e.g., positive dimensions, correct array lengths).
  5. Range Constraints: Must allow optional constraints:
    • Distance (min/max with units)
    • Direction (cardinal or cone-based)
    • Policy (inside, outside, within, between)
    • Tolerance for fuzzy matching
  6. Confidence Level: Must include a numeric confidence score (0–1) to indicate reliability of interpretation.
  7. Metadata: Must allow descriptive metadata for traceability (e.g., DescrMetadata).
  8. Validation Rules Must enforce:
    • Required fields based on CueType (e.g., LocationRef for absolute, RelativeExpression for relative).
    • Pattern matching for relative expressions.
    • Enum constraints for keywords and direction modes.
  9. Extensibility: Must allow future extensions (e.g., additional shapes, new semantic keywords) without breaking existing schema.
  10. Interoperability: Must integrate with higher-level constructs and external schemas (e.g., Location.json).

3      Syntax

https://schemas.mpai.community/OSD/V1.5/data/SpatialCue.json

4      Semantics

Table 1 provides the semantics of the components of Spatial Cue.

Table 1 – Semantics of the Spatial Cue

Label Description
Header Spatial CueHeader
– Standard-SpatialAttitude The characters “OSD-SCU-V”
– Version Major version – 1 or 2 characters
– Dot-separator The character “.”
– Subversion Minor version – 1 or 2 characters
MInstanceID ID of Virtual Space the cue refers to
SpatialCueID Identifier of Spatial Cue entry
SpatialCueData General descriptors for cue context
CoordinateType One of Cartesian, Spherical, Geodesic, Toroidal; used when cue expresses coordinates
ReferenceFrame Frame of reference: World, Entity, Device, or Object:
CueType Nature of the spatial cue: absolute, relative, keyword, region, range
Modality Cue rendering modality: Speech, Audio, Visual, Audio-Visual, Haptic, Smell, RADAR, LiDAR, Ultrasound
Time Temporal bounds and loop flag
Trigger Event or spatial predicate that activates the cue
Position Position data (used for absolute cues)
Orientation Orientation data (used when orientation is relevant)
LocationRef Reference to Location schema (absolute or region anchor)
RelativeExpression Relative spatial expression (e.g., +2m x, left 1m, ahead 3m)
Keyword Semantic cue keyword (near, far, left, right, front, back, up, down, inside, outside)
Region Shape-based target with parameters (sphere, box, cylinder, mesh, mask)
RangeConstraint Constraints around anchor: Distance, Direction, Policy, Tolerance
Confidence Confidence level (0..1)
DescrMetadata Descriptive metadata

5     Conformance Testing

A Data instance Conforms with V1.5 Spatial Cue(OSD-SCU) if:

  1. Its JSON Object validates against its JSON Schema.
  2. Any included  JSON Object validates against its JSON Schema.
  3. All Data in the JSON Object:
    1. Have the specified Data Types.
    2. Conform with the Qualifiers signaled in their JSON Schemas.

6     Performance Assessment