All structural elements can be given identifiers, i.e. names. Names are case sensitive and need to start with a letter or underscore. After the first initial letter numbers and letters may follow. Names need not be unique: Two elements can have the same name without Karamba3D complaining. Each element has a default identifier: its index. This is the reason why it is not allowed to have an integer number as an element identifier. Fig. 3.1.15.1 shows how a list of elements can be split into two data trees using their identifiers. The “Dispatch Elements"-component expects a list of elements in “Elems” as well as a list of identifiers or regular expressions in “Id”. Regular expressions need to be prefixed by a “&”. They represent a very mighty selection tool. In fig. 3.1.15.1 one can see three use-cases: