Implementing Low-Code Solutions

The next step after modelling the solution is to implement the solution. The following chapter describe how to proceed with the implementation of the solution.

In order to implement behavior for a solution Commands, Services, Events and Operations are used. These elements have scope with regards to what they can call or be called from, below is a description of each element and their scope of elements they can call.

Note: Currently for Java low-code solutions only Operations are available.

Factory Command

  • Creates an instance of a root entity and persists it in the data-store
  • Inside a factory command, solution engineers can call Events
  • Inside a factory command's implementation, there is a function called available(). This is used to check the necessary pre-conditions of the command. If the function returns true then the command will be executed, otherwise, the command will not be executed at all

Instance Command

  • Manipulates the values of one or more properties of an already existent instance of an entity
  • Inside an instance command, solution engineers trigger Events
  • Inside an instance command's implementation, there is a function called available(). This is used to check the necessary pre-conditions of the command. If the function returns true then the command will be executed, otherwise, the command will not be executed at all

Domain Service

  • Can perform operations throughout different domain namespaces
  • Inside a domain service, solution engineers can call Factory Command, Instance Command, Domain Service, and Events

Events

  • They are published to indicate that some state has changed
  • An event that is successfully published will automatically execute the script of the Agent that is related to this event

Agents

  • When an event is triggered, then agents are automatically executed as consequence of the action that triggered the event
  • Inside agents, solution engineers can call Factory Command, Instance Command and Domain Service, and trigger Events

Operation

Can perform operations throughout different domain namespaces

Inside Operation, solution engineers can call Factory Command, Instance Command, Domain Service

Illustrative table for the scope of implementation elements

CALLEE
CALLER Factory command Instance command Domain service Events Agent Operation
Factory command √
Instance command √
Domain service √ √ √ √
Events √
Agent √ √ √ √
Operation √ √ √