Function
Ref. Model
I/O Data
SubAIMs
JSON MData
Profiles
Ref. Software
Conformance
Performance
1 Functions
The Natural Language Understanding (MMC‑NLU) AIM receives an input text that might have been generated by a keyboard or by an MMC‑ASR AIM and produces a refined text (if the input text was produced by an MMC‑ASR AIM) and the Meaning of the input text. The MMC‑NLU AIM may also receive the descriptors of an audio‑visual scene and the ID of an object:
| Receives | Text Object directly input by the Entity. |
| Recognised Text from an Automatic Speech Recognition AIM. | |
| The ID of an Instance. | |
| The Audio‑Visual Scene Descriptors containing the Instance ID. | |
| Refines | Input Text if coming from an Automatic Speech Recognition AIM. |
| Extracts | Meaning (Text Descriptors) from Recognised Text or Entity’s Text Object. |
| Produces | Refined Text. |
| Text Descriptors (Meaning). |
2 Reference Model
Figure 1 depicts the Reference Model of the Natural Language Understanding (MMC‑NLU) AIM.

Figure 1 – The Natural Language Understanding (MMC‑NLU) AIM
3 I/O Data
Table 1 specifies the Input and Output Data of the Natural Language Understanding (MMC‑NLU) AIM.
| Text Object | Input Text. |
| Recognised Text Object | Text from the Automatic Speech Recognition AIM. |
| Instance Identifier | The Identifier of the specific Audio or Visual Object belonging to a level in the taxonomy. |
| Audio-Visual Scene Geometry | The digital representation of the spatial arrangement of the Visual Objects of the Scene. |
| Visual Instance Identifier | The Identifier of the specific Visual Object belonging to a level in the taxonomy. |
| Meaning | Descriptors of the Refined Text. |
| Refined Text Object | The refined version of the Recognised Text from the NLU AIM. |
4 SubAIMs
No SubAIMs.
5 JSON Metadata
https://schemas.mpai.community/MMC/V2.5/AIMs/NaturalLanguageUnderstanding.json
6 Profiles
The Profiles of the Natural Language Understanding (MMC‑NLU) AIM are specified.
7 Reference Software
Not part of this specification.
8 Conformance Testing
Table 2 provides the Conformance Testing Method for the MMC‑NLU AIM.
If a schema contains references to other schemas, conformance of data for the primary schema implies that any data referencing a secondary schema shall also validate against the relevant schema, if present, and conform with the Qualifier, if present.
| Text Object | Shall validate against Text Object schema. Text Data shall conform with Text Qualifier. | |
| Recognised Text | Shall validate against Text Object schema. Text Data shall conform with Text Qualifier. | |
| Instance ID | Shall validate against Instance ID schema. | |
| Audio-Visual Scene Geometry | Shall validate against AV Scene Geometry schema. | |
| Refined Text | Shall validate against Text Object schema. Text Data shall conform with Text Qualifier. | |
| Meaning | Shall validate against Meaning schema. |
Table 3 provides an example of MMC‑NLU AIM Conformance Testing.
| Input Selector | Binary data | All Input Selectors shall conform with Selector. |
| Text Object | Unicode | All input Text files to be drawn from Text files. |
| Recognised Text | Unicode | All input Text files to be drawn from Text files. |
| Meaning | JSON | All JSON files shall validate against Meaning schema. |
| Refined Text | Unicode | All Text files produced shall conform with Text. |
The four taggings: POS_tagging, NE_tagging, dependency_tagging, and SRL_tagging must be present in the output JSON file of Meaning. Any of the four tagging values may be null.
9 Performance Assessment
Not part of this specification.