Feature Model Diagram

A Feature Model Diagram is particularly useful for representing the options and configurations available in a software product, making them essential for product line engineering and software configuration management. Feature Model Diagrams help stakeholders understand the complexities and variability of software features, enabling better decision-making regarding product development and customization.

When is a Feature Model Diagram Useful?

Feature Model Diagrams are most useful during the planning and design phases of software development, especially when dealing with:

Configuration Management: To understand and document the different configurations and customizations available for a software product.
Requirements Engineering: To analyze and specify the requirements of software systems, particularly when dealing with optional and alternative features.
Decision Making: To facilitate the selection of features and configurations by stakeholders, developers, or automated configuration systems.

Feature Model Diagram Explained

Feature

A feature represents a distinguishable characteristic, functionality, or aspect of a system that holds significance for some stakeholder. Features are typically organized in a hierarchical structure, illustrating how higher-level features may be decomposed into more specific, lower-level features. This hierarchical arrangement facilitates a comprehensive understanding of the system's capabilities and options.

Mandatory

A mandatory feature is one that must be included in any configuration of the system. It is essential for the functionality of the system or product, indicating that the presence of the parent feature necessitates the inclusion of the mandatory feature. In diagrams, mandatory features are denoted by a filled circle connector to their parent feature, emphasizing their obligatory nature.

Optional

An optional feature is not required for the system to function and may be included or excluded based on specific requirements or preferences. This flexibility allows for a variety of configurations to accommodate different needs or scenarios. Optional features are represented by an empty circle connector.

Or

The Or relationship signifies that out of the child features connected to a parent feature, at least one must be selected if the parent is included. This allows for multiple child features to be selected simultaneously, offering flexibility in the configuration. The representation of the Or relationship in diagrams is with an arc connecting the child features to a filled arc over the line connecting them to the parent feature, indicating the possibility of selecting one or more of these features.

Alternative

An Alternative relationship (or as exclusive or - XOR) dictates that exactly one of the child features must be selected when the parent feature is included. This is used when the child features are mutually exclusive options for a particular aspect of the system. The depiction of the Alternative relationship in diagrams is with an arc connecting the child features to an empty arc over the line that connects them to the parent feature, emphasizing the exclusivity in the choice among the child features.

Requires

The Requires relationship is depicted as an arrowed connector that points from the feature that imposes the requirement to the feature that is required. This visual representation underscores the dependency between features, indicating that the presence of one feature necessitates the inclusion of another specific feature within the system configuration. This relationship is fundamental for defining conditional dependencies that ensure the coherence and completeness of feature selections.

Excludes

The Excludes relationship is represented by a double arrowed line between two features, signifying that the selection of one feature prohibits the inclusion of the other within the same system configuration. This graphical notation is crucial for highlighting incompatibilities or conflicts between features, ensuring that mutually exclusive features are not selected simultaneously. The Excludes relationship is key to avoiding invalid configurations by clearly delineating features that cannot coexist.

Feature Model Diagram Overview

Creating a Feature Model Diagram in Software Ideas Modeler

Software Ideas Modeler offers robust support for creating Feature Model Diagrams, starting from the Premium edition. The diagram type is accessible from the 'Other' group in the diagram menu. Here's how to create one:

Add a Feature Model Diagram: Navigate to the 'Other' group in the diagram menu and select 'Feature Model Diagram'. A new diagram canvas will be created.
Add Features: Use the toolbox to add 'Feature' elements to the diagram (drag and drop them or specify exact bounds in the diagram canvas). Each feature represents a functional or non-functional characteristic of the system.
Define Relationships: Utilize the different relationship types to define how features relate to each other:

Mandatory Relationship: Indicates that a subfeature is essential if the parent feature is selected.
Optional Relationship: Indicates that a subfeature is optional.
Or Relationship: Represents a choice among subfeatures; at least one must be selected if the parent is included.
Alternative Relationship: Similar to 'Or', but specifies that exactly one of the subfeatures must be chosen.
Requires: Specifies that the inclusion of one feature requires the inclusion of another.
Excludes: Indicates that the inclusion of one feature prohibits the inclusion of another.

Use Context Bar for Subfeatures: To add subfeatures efficiently, utilize the context bar. It offers buttons for Alternative, Or, Mandatory, and Optional features, ensuring they are connected properly to their parent features.
Finalize the Diagram: Arrange the features and relationships on the canvas to clearly convey the structure and dependencies of your system's features.