com.liferay.portal.kernel.workflow
Interfaces 
WorkflowDefinition
WorkflowDefinitionManager
WorkflowEngineManager
WorkflowHandler
WorkflowHandlerRegistry
WorkflowInstance
WorkflowInstanceManager
WorkflowLog
WorkflowLogManager
WorkflowStatusManager
WorkflowTask
WorkflowTaskManager
Classes 
ContextConstants
DefaultWorkflowDefinition
DefaultWorkflowInstance
DefaultWorkflowLog
DefaultWorkflowTask
StatusConstants
WorkflowDefinitionManagerUtil
WorkflowEngineManagerUtil
WorkflowHandlerRegistryUtil
WorkflowInstanceManagerUtil
WorkflowLogManagerUtil
WorkflowStatusManagerUtil
WorkflowTaskManagerUtil
Exceptions 
RequiredWorkflowDefinitionException
WorkflowDefinitionFileException
WorkflowException
WorkflowTaskDueDateException