UCM13 — define port types for “pull-pull” interactions

The UCM core library defines the message connector in which the data producer pushes data to the connector, and the connector pushes data to the consumer. This more or less corresponds to the event interactions of CCM.

Yet, in some situations, pulling data from the producer is a good architectural choice. For example, if we want to ensure a piece of data is sent periodically, it is best to let the connector manage this, instead of the component: even if there are bugs in the component business code, that connector shall periodically fetch the data.

It might be difficult to standardize a “pull-pull” connector because there could be many different situations: periodic fetching, fetching upon request from the consumer, etc. The UCM standard should simply define port types in order to have standard APIs.

define a data pull connector

Define a data pull connector in the extended interactions. This connector involves one supplier and one or more consumers. Whenever a consumer pulls a piece of data, the piece of data is fetched from the supplier.