# Architectural Refactorings

Within this section, we provide a documentation of all architectural refactorings (ARs) available in the Context Mapper tool.

## Motivation: Why refactorings?

The provided refactorings offer the advantage that the result is always a correct CML model which compiles without errors. If you perform similar changes manually, you also have to fix upcoming errors within the Context Map manually. The AR’s ensure that corresponding references and dependencies in other parts of the model are respected and adjusted if necessary.

## Architectural Refactoring Categories

The ARs are divided into the following categories:

**Structural Refactorings**: Change the structure of the decomposition (impact on Bounded Contexts and/or Aggregates).**Relationship Refactorings**: Just change the type of a relationship on the Context Map, but do not change the structure of the decomposition.

## Refactoring Overview

The Context Mapper tool offers you a set of architectural refactorings which can be applied to your CML models. The refactorings shall support you with evolving and improving the architecture of your system.

### Structural Refactorings

We currently provide the following structural ARs:

Name | Subject | Description | Input | Output |
---|---|---|---|---|

AR-1: Split Aggregate by Entities |
Aggregate | Splits an aggregate which contains multiple entities and produces one aggregate per entity. | 1 Aggregate | n Aggregates |

AR-2: Split Bounded Context by Use Cases^{1} |
Bounded Context | Splits a bounded context by grouping those aggregates together into one bounded context which are used by the same use case(s). | 1 Bounded Context | n Bounded Contexts |

AR-3: Split Bounded Context by Owner^{1} |
Bounded Context | Splits a bounded context by grouping those aggregates together into one bounded context which belong to the same team. | 1 Bounded Context | n Bounded Contexts |

AR-4: Extract Aggregates by Volatility |
Bounded Context | Extracts all aggregates from a bounded context by a given volatility, or likelihood for change (RARELY, NORMAL or OFTEN), and moves them to a separate context. | 1 Bounded Context | 2 Bounded Contexts |

AR-5: Extract Aggregates by Cohesion |
Bounded Context | Extracts a set of aggregates which are chosen by certain cohesion criteria and moves them to a separate bounded context. | 1 Bounded Context | 2 Bounded Contexts |

AR-6: Merge Aggregates |
Aggregate | Merges two aggregates within a bounded context together to one aggregate. | 2 Aggregates | 1 Aggregate |

AR-7: Merge Bounded Contexts |
Bounded Context | Merges two bounded contexts together. The result is one bounded context containing all the aggregates of the two input boundedcontexts. | 2 Bounded Contexts | 1 Bounded Context |

AR-8: Extract Shared Kernel |
Shared Kernel relationship | Extracts a new bounded context for the common model parts of the Shared Kernel and establishes two upstream-downstream relationship between the new and the existing Bounded Contexts. | 1 Shared Kernel relationship | 1 New Bounded Context and 2 new upstream-downstream relationships |

AR-9: Suspend Partnership |
Partnership relationship | Suspends a Partnership relationship and replaces it with another structure how the two Bounded Context can depend on each other. The AR provides three strategies to suspend the partnership. | 1 Partnership relationship | Depends on the selected mode |

^{1}: An aggregate in CML can be used by **multiple** use cases and is owned by **one** owner (team).

### Relationship Refactorings

The following ARs to change Context Map relationships are currently implemented:

Name | Subject | Description | Input | Output |
---|---|---|---|---|

AR-10: Change Shared Kernel to Partnership |
Shared Kernel relationship | Changes the type of a Shared Kernel relationship to a Partnership relationship. | Shared Kernel relationship | Partnership relationship |

AR-11: Change Partnership to Shared Kernel |
Partnership relationship | Changes the type of a Partnership relationship to a Shared Kernel relationship. | Partnership relationship | Shared Kernel relationship |

## Examples

Within our examples repository you can find input and corresponding output examples for all ARs listed above.

## How to apply Architectural Refactorings (ARs)

Architectural refactorings can be applied within the Context Mapper Eclipse plugin by using the context menu in the DSL editor. With a
right-click on a bounded context or an aggregate the **Context Mapper: Refactor** menu entry appears and lists all refactorings which are
applicable to the selected elements:

**Note** that the context menu only shows ARs for which your selected model element fulfills the preconditions.
The preconditions for all ARs are mentioned on the corresponding detail pages linked above.

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