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

1      Definition

The Spatial Anchor Data Type represents a physical or conceptual reference used to determine position, orientation, or spatial relationships in a Space. A Spatial Anchor may refer to an absolute location, a relative object, a semantic zone, or a defined 3D volume, enabling consistent multimodal interpretation of spatial cues and interactions.

2      Functional Requirements

  • Anchor Classification – The Data Type shall represent the anchor category as one of the following:
    • absolute – an exact spatial reference;
    • relative – relative to another object or entity;
    • semantic – a named human‑interpreted zone;
    • volume – a spatial region represented as a 3D volume.
  • Absolute Anchoring – When AnchorType is absolute,
    the Data Type may reference a fixed Location.
  • Relative Anchoring – When AnchorType is relative, the Data Type shall identify the reference object via ReferenceObject.
  • Semantic Anchoring – When AnchorType is semantic, the Data Type shall specify a conceptual or functional area via SemanticZone.
  • Volume Anchoring – When AnchorType is volume, the Data Type shall provide a reference to a spatial volume description via LocationRef.
  • Confidence – The Data Type shall allow encoding of confidence (0..1) in the anchor’s interpretation.

3      Syntax

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

4      Semantics

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

Table 1 – Semantics of the Spatial Anchor

Label Description
Header Spatial Anchor Header – Standard “OSD-SAN-Vx,y”.
MInstanceID ID of Virtual Space the Spatial Anchor refers to.
SpatialAnchorID Identifier of this Spatial Anchor instance.
AnchorType Nature of the spatial anchor. One of:
• absolute – fixed spatial reference;
• relative – anchored to a reference object;
• semantic – named human-meaningful zone;
• volume – spatial region described using a 3D Location structure.
LocationRef Reference to a spatial 3D Location (as defined in OSD/V1.5/Location.json).
Required when AnchorType = volume.
ReferenceObject Identifier of the object used as the spatial reference point for relative
anchoring. Required when AnchorType = relative.
SemanticZone Name of a semantically meaningful area or zone (e.g., “kitchen”, “stage_left”,
“meeting room”). Required when AnchorType = semantic.
Confidence Confidence score (0..1) indicating reliability of the anchor interpretation
or the certainty that the anchor reference is correct.
DataExchangeMetadata Metadata optionally supporting regulated or controlled exchange of Interaction Potential Data, as defined by AIF V3.0.
Trace Provenance information defined by AIF V3.0, identifying the producing AIM, generation time, and related metadata.
DescrMetadata Descriptive metadata (maximum 2048 characters) supporting annotation, documentation, or indexing.

5     Conformance Testing

A Data instance Conforms with V1.5 Spatial Anchor (OSD-SAN) 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