There must be a way to supply the parameters required by a method in order to invoke it in the workflow engine. The workflow engine has a pool of data at its disposal in the form of workflow data objects (see Workflow Data Objects). Input mappings are used to declare which workflow data object attributes will be used to populate the values of the specific method parameters when the method is invoked. Input mappings are optional where struct fields have been specified as method parameters. However, primitive base type parameters must be mapped.