Module derived 

Derived attack closure per Cayrol & Lagasquie-Schiex 2005 and Amgoud et al. 2008 §3.

Given a BipolarFramework, compute the set of all attacks (direct plus derived) that hold under necessary-support semantics. Three derivation rules:

1. Direct: every edge in the attack set is an attack.
2. Supported: if A transitively supports X and X directly attacks B, then A attacks B.
3. Secondary/Mediated: if A directly attacks X and X transitively supports C, then A attacks C. (Amgoud et al. distinguishes secondary and mediated but both produce the same edges under the necessary-support reading.)

The closure is computed as a fixed point over all three rules applied together. For a framework with n arguments, convergence is bounded by n iterations and the closure has at most n² edges.

Functions

closed_attacks

Compute the closed attack set for a bipolar framework under necessary-support semantics.