An irreducibly inconsistent system of constraints (IIS) is a minimal s
et of infeasible constraints. MINOS(IIS) is a modified version of MINO
S 5.3 which analyzes an infeasible LP model and reports the constraint
s which constitute an IIS. This localization of the problem speeds the
diagnosis and subsequent repair of the model considerably. The paper
concentrates on the practical implementation of the filtering algorith
ms used for IIS localization in MINOS(IIS). New extensions to the algo
rithm which permit external guidance of the IIS localization are also
presented.