An additional consideration is that we would like to focus on the discovery of novel or non-obvious DE operators.
for a given candidate DE operator c, we compute p F byNPI pcq: the value of F byNPI pcq that results if we discard all NPI contexts containing a DE operator on a list of 10 wellknown instances, namely, 'not ', 'n't', 'no', 'none', 'neither', 'nor', 'few', 'each', 'every', and 'without'.