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