Am Wed, 1 Oct 2014 17:39:46 +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? 
> 
> Now I see what you mean and I agree with you. But I guess I'd choose the
> second case between the two following cases:
> 
> 1. deliberately providing a many-to-one relation between keys and value,
>    and writing code that ensures all these values of all theses *number*
>    keys lead to the single issue's number,
> 2. be careful in providing a one-to-one relation between a single
>    "number" key and issue's number value, and being able to specify that
>    this key is required.

That was what I meant with that you need to be careful to define and
use "basic keys". 

Beside this there is also the timing problem Joseph mentioned: when
should be tested if a key has been used? It is obviously not the key
code of the key that can do it. So imho you are not looking for a
.required property but a .enableifsettest property which adds and
sets some boolean which you can later check.  



-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/