Patterndepends

Patterndepends is a conceptual mechanism in pattern-oriented design and template-based systems that expresses a dependency relationship between patterns. A pattern may declare that it can be applied only when another pattern is present or when certain conditions are met. The term is used in discussions of pattern languages and in some domain-specific tooling to describe how patterns influence one another.

In practice, patterndepends is modeled as a dependency graph, with nodes representing patterns and directed edges indicating that one pattern depends on another. Resolution algorithms traverse this graph to determine a valid combination and execution order. Systems may allow conditional dependencies, such as Patterndepends(P, Q, cond), where cond is a predicate over context, configuration, or results of P and Q. Some implementations support cycles handling, constraints, and version or capability compatibility checks.

Examples of patterndepends appear in various domains. A user interface pattern for adaptive layouts may depend on a LayoutOrientation pattern. A data processing pipeline pattern may depend on a Logging pattern to ensure traceability. A serialization pattern may depend on a VersionedSchema pattern to guarantee compatibility across formats.

Benefits of using patterndepends include enforcing coherent composition, enabling automated validation, and guiding tooling for code generation or runtime assembly. Potential drawbacks include the risk of cyclic dependencies, ambiguous constraints, and added complexity in maintenance and understanding.

Related concepts include dependency management, feature modeling, and pattern languages. Patterndepends emphasizes conditional applicability beyond mere presence of patterns, and is used to reason about how pattern combinations affect system behavior.