  AvailBaseQueryCriteria | A collection of information about the locations for which availability is to be checked. It may be repeated to query availability of each individual train in multiple train segments for a specified route. Defines rail availability and schedule search criteria, including origin-destination information and train number and network code. |
| PassengerType | Specify passenger type/category.Classification of passenger demographics and rate qualifying information. |
| RailPrefs | Specifies the preferences for the availability request.Defines information used to express traveler preferences when requesting rail avilability information. |
| ReturnInfo | Indicates the date and time search criteria for the return journey.Date and time of trip that allows specifying a time window before and after the given date. |
| TPA_Extensions | A placeholder in the schema to allow for additional elements and attributes to be included per Trading Partner Agreement (TPA).Allows extensions to be added to the OpenTravel specification per trading partner agreement. |