Am Wed, 1 Oct 2014 16:46:13 +0200 schrieb [log in to unmask]: >> It is normally not the *key* that is required but a *value* > > Except if some keys are considered as mandatory arguments (and they > could not be turned into arguments because keys are much more explicit > than arguments). No, it is still the value you want. E.g assume that beside your keys you also define a key numbermonth=143/6 and a key numberdate=143/6/2014 and a key extranumber=143/b and a key issuenumber as alias to number. All set the needed value 143. So which key do you want to declare as required? >> Imho it is easier and more logical to test for the value and emit an >> error if is doesn't exist. > OK but, AFAICS, there isn't any high level key property for this (and > that's the point of this thread): The question is if the high level key property is the correct place to declare such a requirement on a value. >> (Actually I wouldn't emit an error. As almost everyone is using >> scrollmode today error message are often ignored. > Most of the TeX editors highlight errors, no? At least it is the case > for TeXstudio, for instance. Sure but a lot of users tend to ignore them as long as the document compiles. They often don't understand what the error means and so turn a blind eye on it. You wouldn't believe how many people start the correct errors only when the 100-error limit is reached and nothing works ;-) -- Ulrike Fischer http://www.troubleshooting-tex.de/