Existence declarations are the simplest declarations you can create. Each of these declarations must be fulfilled for the document or rule to match. However, for each possible combination multiple matches are created.
VARIABLE is ONTOLOGY, ROLE_1, ..., ROLE_N
A match with the name VARIABLE is created for an Instance that has the Ontology ONTOLOGY and all the roles (ROLE_1 to ROLE_N) mentioned.
A declaration is also valid if there is either an Ontology or a list of Roles after the is; providing both of them is optional.
Example: Just an Ontology
p is Person
If there is a Person Instance in the Case, it will be available in the variable p.
Example: Just a Role
p is AccountHolder
If there is an Ontology Instance with the role AccountHolder in the Case, it will be available in the variable p.
Example: Ontology and Role
p is Person, AccountHolder
If there is a Person Instance that has the Role AccountHolder in the Case, it will be available in the variable p.