private Set<String> generateOperations(Collection<String> filtertypes, Collection<String> charsForAttribute, int attLength, Collection<String> charsForValue, int valLength) {
        Set<String> allOperations = new HashSet<String>();
        Set<String> allValuesWithSubstring = createPermutations(charsForValue, valLength, true);
        Set<String> allValuesWithoutSubstring = createPermutations(charsForValue, valLength, false);
        for (String att : createPermutations(charsForAttribute, attLength, false)) {
            for (String fil : filtertypes) {
                if (fil.equals("=")) {
                    //Substrings are only allowed using '='
                    for (String val : allValuesWithSubstring) {
                        allOperations.add("("+att+fil+val+")");
                    }
                }
                else if (fil.equals("=*")) {
                    allOperations.add("("+att+fil);
                }
                else {
                    for (String val : allValuesWithoutSubstring) {
                        allOperations.add("("+att+fil+val+")");
                    }
                }
            }
        }

        return allOperations;
    }