| Name | Description |
| client | A producer or consumer of metadata. |
| channel | A is an object on which metadata can be sent. Is created by instantiating a channel object and is uniquely identified by its topic and source. |
| producer | A application that produces metadata over a channel on the metadata broker. |
| consumer | A application that subscribes to one or more channels. |
| subscriber | A subscriber is an object that makes it possible to subscribe to a channel and receive published metadata. |
| topic | A textual string that identifies a metadata channel. Access control is configured on the topic. |
| source | Similar metadata can be separated into several channels under one topic. The channels has a source, e.g. '0', '1', 'masked'. Access control can only be enforced on topic level, NOT on a source level. |
| payload | The payload is the data published by producers to channels, and received by the consumers through subscribers. |
| info | Information that does not change during the lifetime of the channel object, such as calibration tables and how the metadata published by a producer is structured and what data it supports. A consumer can request the info from a producer. |
