A signature thus provides a conceptual glossary in whose terms everything else in the symbolic model must be described, similar to an English dictionary for the English language. Additionally, a signature comprises information to capture certain aspects of the ontology of an architecture. For example, it may include hierarchical information between sorts in terms of an ‘is-a’ relationship, or containment information in terms of an ‘includes’ relationship, or dependency information in terms of a ‘requires’ relationship. Signatures that contain this additional information are more general than a glossary. They provide a conceptual schema, similar to the schema provided to biologists by the species classification.