Aspect data transports

With Bosch Semantic Stack, data is provided by aspects and described by the corresponding Aspect Models. However, there are multiple ways to access an aspect’s data. Currently, two protocols are supported: HTTP and MQTT.

Both protocols have their strengths and weaknesses. It depends on the use case which should be preferred for the implementation of an aspect. Registering an aspect in the Digital Twin Registry requires the Aspect Model identifier, the type of aspect and the aspect endpoint.

You can find more information on each type of endpoint in the respective sections on HTTP and MQTT.

Table 1. Comparison: HTTP aspect endpoints vs. MQTT aspect endpoints
Feature	HTTP endpoint	MQTT endpoint
Valid endpoint URL	Any `http://` or `https://` URL	Any `mqtt://`, `mqtts://`, `tcp://` or `ssl://` URL
Valid endpoint types	`READ`, `FILTER`, `OPERATIONS`	`READ`, `OPERATIONS`
Data access	Poll data via `HTTP GET`	Subscribe to topics
Filtering	Via RQL — Details…	N/A
Authentication	Via OAuth — Details…	N/A
Invoke Operations defined in the Aspect Model	Via JSON-RPC	Via corresponding topic
Receive Events defined the Aspect Model	N/A	Via corresponding topic