We aim at assisting developers to write, in a Hoare style, provably correct graph transformations expressed in the ALCQ Description Logic. Given a postcondition and a transformation rule, we compute the weakest precondition for developers. However, the size and quality of this formula may be complex and hard to grasp. We seek to reduce the weakest precondition’s complexness by a static analysis based on an alias calculus. The refined precondition is presented to the developer in terms of alternative formulae, each one specifying a potential matching of the source graph. The developer chooses then the formulae that correspond to his intention to obtain finally a correct-byconstruction Hoare triple.