Today, the server has capabilities for MaxArrayLength, MaxStringLength, and MaxByteStringLength (and maybe array dimensions). This is of limited value for PubSub.
Each variable used in PubSub "should" specify it max length.
IF you don't specify it for each variable, then you "could" specify it for all variables used in a functional entity (which will require a new capability to be defined).
Finally, if you do neither of these things, your max lengths are defined by the values specified for the server (not recommended if you use strings in your datasets).

Added text to indicate input and output variable should include the recommended properties (or the server level version would apply)

Added text explaining MaxStringLength property and that it shall be assigned to variable in certain cases (Also MaxByteStringLength)