# Structs
A Controller is the handler of all API REST calls matching the stack model It forwards API requests to the stack instance identified by the GONG_StackPath parameters in the request the stack instance is the BackRepo instance.
A GenericError is the default error message that is generated.
An PredecessorID parameter model.
PredecessorInput is a schema that can validate the user’s input to prevent us from getting invalid data swagger:parameters postPredecessor updatePredecessor.
An ProjectID parameter model.
ProjectInput is a schema that can validate the user’s input to prevent us from getting invalid data swagger:parameters postProject updateProject.
An TaskID parameter model.
TaskInput is a schema that can validate the user’s input to prevent us from getting invalid data swagger:parameters postTask updateTask.
A ValidationError is an that is generated for validation failures.