todepends

Todepends is a term used in dependency modeling to denote the transitive set of dependencies that a node requires. In software packaging and build systems, the todepends of a package is the collection of all packages that must be present for the package to build, test, or run, including those reached through indirect dependencies.

Formal description: Model the situation as a directed graph G = (V,E) where an edge (u,v) indicates that u directly depends on v. The todepends of a node u, denoted todepends(u), is the set of all nodes v such that there exists a directed path from u to v in G. By convention, v ≠ u.

Computation and use: Todepends can be computed by traversal algorithms such as depth-first search or breadth-first search starting from u, or by maintaining a transitive closure. Many package managers compute or store the transitive dependency set to speed up resolution and to assess install footprints. The set may be constrained by version requirements, optional dependencies, and conflict rules.

Example: If A depends on B and C, and B depends on D, then todepends(A) = {B, C, D}, assuming D is required by B. If D is optional for A but needed for certain features, the todepends may be described with a flag indicating optionality.

Limitations and context: Cycles in the dependency graph complicate the notion of todepends and require cycle detection. Real-world systems may differentiate between mandatory, recommended, and optional dependencies, or separate runtime and build-time dependencies. The term itself is not universally standardized and appears mostly in theoretical discussions or experimental tooling.

See also: transitive closure, depends_on, dependency graph, package manager.