startswithcapital(s) - true if string s starts with
a capital letter or is empty
startswithlowercase(s) - true if string s starts with
a lower case letter or is empty
islowercase(s) - true if all letters in string s
are lower case or if s is empty
Boolean functions operating on sets:
isunique(s) - true if s is a regular set or if s is a
multiset that contains no element more than once.
Boolean functions operating on model elements:
instanceof(e,s) - true if the type of model element e
is s or a subtype of s. For example, instanceof(context, 'package')
is true if the owner of the element is a package or a subtype
of package.