Identifiers are used to name different kinds of language objects such as nodes, hyperedges or variables. Identifiers may contain letters, numbers, underscores, and dollar signs but must begin with a letter or an underscore.
Accordingly, the following identifiers are all valid,
Besides these lexical requirements, identifiers must also be unique in their respective scope. Hence, no two nodes may have the same identifier since this would prohibit the unambiguous identification of a particular node.
Similarly, variables and parameters may not have the same identifier as a node or other variables and parameters belonging to the same node.
