Metadatas

Astoria introduces the concept of ‘metadata’, used here as a specific technical term.

Metadata is a specific set of mutable and immutable data that defines the environment that the robot is running in.

Examples of metadata include: robot starting zone, development mode indicator

Metadata is managed by the Astmetad state manager. Metadata must conform to the schema, which is defined in astoria.common.metadata.Metadata.

Metadata Resolution

Metadata is ‘resolved’ during runtime by overlaying a number of metadata sources.

All metadata attributes must be present, even if the value of an attribute is None.

Sources are overlaid in priority order. The highest priority source is overlaid last such that it can override data from lower-priority sources.

For example:

  • Initial metadata is generated.

    • Metadata is {"foo": 1, "bar": 2, "bees": "hive"}

  • First Overlay: {"foo": 2, "bar": 3}

    • Metadata is {"foo": 2, "bar": 3, "bees": "hive"}

  • Second Overlay: {"bar": 0, "bees": "wasp"}

    • Metadata is {"foo": 2, "bar": 0, "bees": "wasp"}

Metadata Source

Metadata sources are of the type Dict[str, str], where the key is the name of the attr to be overridden and the value is the overriding value.

A metadata source must be defined in the code for Astmetad and cannot be dynamically registered.

A metadata source must have a set of attributes that it is able to override. No metadata source should be able to arbitrarily override.

Any spurious attributes in the metadata source will have no effect. astmetad will give a warning though.

Currently implemented sources: