We define a potentialist system of ZF-structures, that is, collection possible worlds in the language ZF connected by binary accessibility relation, achieving account full background set-theoretic universe $V$. The definition involves Berkeley cardinals, strongest known large cardinal axioms, inconsistent with Axiom Choice. In fact, as theory we assume just ZF. It turns out propositional modal ...

The need for interaction between customer and supplier during the production of a service makes it difficult to measure and evaluate the soft factors of a service process. They cannot be measured by using objective measuring equipment. Soft factors rather have to be measured and evaluated by people who function as subjective measuring equipments. The use of Likert scales is the common way to me...