docs: function schema (controller, args) {
      // get model
      var model = controller.model
      // if action set then try to get action model
      if (args.action) {
          // require action model
          if (!model.actionModels[args.action]) {
              httpError(400, 'Invalid Action')
          }
          // use action model to get schema
          model = model.actionModels[args.action]
      }
      // get data column name for model
      var dataColumn = model.columnName('data')
      // if meta is set or there is no data column return entire schema 
      // otherwise return only schema for data
      return args.meta || !model.schemaData
          ? model.schemaMeta
          : model.schemaData
  }