WorkflowDefinition
    graph       (WorkflowGraph SqlBackendKey SqlBackendKey) -- FileId, UserId
    scope       WorkflowInstanceScope'
    name        WorkflowDefinitionName 
    UniqueWorkflowDefinition name scope

WorkflowDefinitionDescription
    definition  WorkflowDefinitionId
    language    Lang
    title       Text
    description Html Maybe
    UniqueWorkflowDefinitionDescription definition language

WorkflowInstance
    definition  WorkflowDefinitionId Maybe
    graph       (WorkflowGraph SqlBackendKey SqlBackendKey)  -- FileId, UserId
    scope       (WorkflowInstanceScope SqlBackendKey SqlBackendKey SqlBackendKey)  -- TermId, SchoolId, CourseId
    name        WorkflowInstanceName
    category    WorkflowInstanceCategory Maybe
    UniqueWorkflowInstance name scope

WorkflowWorkflow
    instance    WorkflowInstanceId Maybe
    graph       (WorkflowGraph SqlBackendKey SqlBackendKey)  -- FileId, UserId
    initUser    UserId Maybe
    initTime    UTCTime
    state       (WorkflowState SqlBackendKey SqlBackendKey)  -- FileId, UserId
    currentNode WorkflowGraphNodeLabel