Starting from top left and going counter-clockwise, we have the following elements. The Application that is to be developed has certain Characteristics (see also 1. Maintainable Applications). Some Characteristics
Characteristics of Decoupling Patterns
Each decoupling pattern has different characteristics. These characteristics have to match with the quality requirements of your application. we state the characteristics that are most important for this type of decoupling. Other characteristics may be interesting for other decoupling types.
| Type | Description | |
|---|---|---|
| Knowledge characteristics | User set or System set | Is there a certain moment when you want to make a decision (explicitly), or do you want that the rule engine with its truth maintenance takes over and derives the value when needed (implicitly)? |
| Parameters or complex model | For decoupling, input and output parameters are needed These parameters receive a value from attributes in your domain. In the most extreme cases, no parameters are needed at all, or the complete domain acts as input. Certain patterns favor simple parameters, others favor complex parameter sets. In case that a large part of the domain is needed is input, and your domain can not be simplified significantly, then you might choose not to apply any of the presented decoupling patterns. | |
| Enhanced by Blueriq Functionality | Blueriq has certain features in studio, such as model validations, the Decision Requirements graph, dependencies and specifications which help in creating and maintaining complex applications. Depending on the pattern, these feature can or can not be used. | |
Maintainability characteristics It should be possible to quickly make changes to business rules independent of other functionality. | Focus on Internal or External Use | The functionality might only be used internally, favoring certain decoupling mechanisms. This makes the contract simpler to maintain, as both the exposer and consumer are under control. If the application is also valuable externally, then the contract to the outside world can not be changed as easily. |
| Low Implementation complexity | Each pattern increases the complexity of the model, and some more than others. Does the gain weigh up against the complexity costs? | |
| Internals invisible (encapsulation) | Internals of decoupled functions is invisible or visible for the requesting application. When the internals are not visible, it reduces the mental load on the Business Engineer as well as prevents errors when the internals are used. Business rules must be executed autonomously and have no dependencies with other application features. When this is achieved, the internals can be safely refactored without side-effects. | |
| Autonomous | Business rules must be executed autonomously and have no dependencies with other application features. With a strict separation, side-effects of changes are impossible. When only the internals are hidden (see above), then it might still be possible to have side-effects. However, a knowledge-model may embrace all business rules without decoupling every single rule. | |
| Highly Testable | It must be easy to test the functionality. This includes manual as well as automated tests. | |
| Highly Reusable | Calculations often have to be reused within the Blueriq application landscape. Certain patterns make a component easier to be re-used than other patterns. | |
| Out of the Box | Business rules must be easily modeled and executed with Blueriq by using OOTB functionalities. By preference you want everything to be provided by the product. There are patterns possible, however, that need some custom coding. | |
Deployment characteristics | Deployment Granularity | The pattern can be included in the project, meaning that only when a new version of the application is published the decoupled part is published. Or the decoupled part can be deployed independently, so that when it is published, all projects that use this feature are directly using the new version. |
Design Patterns
These are the decoupling patterns that are available for decoupling domain and business rules.
- Decoupling Pattern 1: Module with Flow
- Decoupling Pattern 2: Webservice call
- Decoupling Pattern 3: Custom service to retrieve data
- Decoupling Pattern 4: Custom decision service
- Decoupling Pattern 5: Function
- Decoupling Pattern 6: External Rule
- Decoupling Pattern 7: AQ_StartProject service
- Decoupling Pattern 8: External Flow Container
For decoupling a business function a.k.a domain service of the domain layer, such as a business decision or calculation, we generally advise patterns Decoupling Pattern 2: Webservice call and Decoupling Pattern 6: External Rule. You need to match the pattern to your specific situation however.
Overview
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