[new rule] add a rule(set) to clearly specify how data change events should be used

[BirgitBader]

(i) This issue has been manually transferred from a former internal repository, as a private repository issue cannot be transferred to a public repository.

Context

Data change events usually do not contain semantical information of why a change happened. This is why the usage of data change events should be limited. Deducting business decisions from data change events implicitly requires domain knowledge of a foreign domain, thus reducing encapsulation.

A rule (or a set of rules) should be created to clearly state how data change events should be used.

Possible rules:

• SHOULD use data change events for data replication
• SHOULD be used for updating otherwise read-only data sources. The only purpose of these read-only data sources is for consumption (e.g. by UIs, report generation, statistics).
• MUST NOT be used to implement policies (automation rules) that issue business side effects (commands) to any API.
• MUST NOT deduct intention from data change events