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Commands
- Commands are a type of activity that occurs in the domain.
- Represents a request to preform an action.
- the action has not yet happened and it can be rejected.
- Usually delivers to aa specific destination causes a change to the state of the domain.
- Eg. Add an item to an order, pay a bill.
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Events
- Events are another type of activities in the domain.
- They represent an action that happened in the past.
- because of the action already completed, they can not be rejected.
- often broadcast to many destinations.
- record a change to the state of the domain, often the result of aa command.
- Eg. item was added to an order, a bill was paid, aa meal was prepared.
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Quereis
- they represent a request for information about the domain.
- because they are a query, a response is always expected.
- usually delivered to a specific destination
- queries should not alter the state of the domain
- Eg. get all the details of an order, check if a bill haas been paid.
relation between command event and query.