main schema e-service developers Revised for version 3.0 Kizoom Limited, by Adam Cohen Rose, Nicholas Knowles. [mailto:schemer@kizoom.com] Specialist advice for version 3.0. Matthew Frances, Action Information Management systems. [mailto:mfrancis@aimltd.co.uk] Overall direction and Advice from Roger Slevin [Roger.Slevin@dft.gsi.gov.uk] United Kingdom Created as W3C .xsd schema by Atkins Global as 2.1 XML schema, Richard Shaw, Mike Ness. mailto:richard.shaw@atkinsglobal.com 2003-05-20 2003-07-30 2003-12-03

JourneyWeb is an XML protocol to allow remote journey planning engines to communicate in order to provide multimodal journeys spanning different regions. The protocol is a UK national de facto standard sponsored by the UK Department of Transport and is being used in the Transport Direct Portal project to provide contiguous distributed journey planning for the whole of the UK. It builds on two other standards NaPTAN and the NPTG gazetteer.

JourneyWeb allows two or more journey planning engines with knowledge of different areas or transport modes to carry out distributed journey planning, that is to dynamically query data from both servers and use the results to build up composite journeys that span the respective areas covered by the respective engines.

JourneyWeb is a request response protocol with messages to query the following:

  • POINTS: The remote stops for a NPTG locality or coordinate.
  • JOURNEYS: Journeys between combinations of stops.
  • LEG DETAILS: Further Details about journey legs.
  • SERVICES: The services covered by a remote timetable.
  • OPERATORS: The operators supported by the remote journey planner.
  • TIMETABLES: A matrix of timetable data for remote services, suitable for producing columnar timetables.
  • STOPEVENTS: Departures for a stop at a specified time.

JourneyWeb results may optionally include map plotting data, disabled access information.

text/xml http://www.w3.org/2001/XMLSchema XML schema, W3C Recommendation 2001 http://www.journeyweb.org.uk/schemas/3.0/JourneyWeb.xsd [ISO 639-2/B] ENG Department for Transport, Great Minster House, 76 Marsham Street, London SW1P 4DR http://www.journeyweb.org.uk/schemas/3.0/ErrorHandling.xsd ErrorHandling Unclassified Crown Copyright 2000-2004. * JourneyWeb concept Originally developed in 1997 by G. P. Fingerle as part of his PhD thesis (final publication in July, 2001). * Revised as Version 1.1 Nov 10 2000 by A. C. Lock and G. P. Fingerle. * Revised as Version 1.1.1 December 12, 2001 by G. P. Fingerle. * Revised as Version 2.0 schema December 12, 2002 by Richard Shaw, Mike Ness WS Atkins. * Revised as Version 2.1 schema May 20, 2002 by Richard Shaw, Mike Ness WS Atkins. Version 3.0 Draft for approval Arts, recreation and travel, Tourism, Travel (tourism), Transport, Air transport, Aircraft (civilian), Airports, Aviation, Ports and maritime transport, Ferries (marine), Maritime transport, Sea transport, Water transport (sea-going) Public transport, Bus services, Coach services, Bus stops and stations Rail transport, Infrastructure (railways), Railway stations and track, Train services, Underground trains Roads and road transport, Car parks, Cars (road vehicles), Cycling (transport), Highways, Infrastructure (roads), Minicabs, Motorcycles, Parking, Pavements, Road signs, Taxis, Vehicles (road use), Walking (as transport), Access for disabled people, Mobility for the disabled Transport Direct JourneyWeb, an XML protocol for distributed journey planning. Standard @SchemaVersion Only responses valid for the requested version of the schema will be returned. @Language (optional) ISO639 value. @SuppressNames (optional). Contains one or more specific requests. @RequestID Request the points for a remote locality or X,Y. @RequestID Request a journey between A and B. @RequestID Request more information about a specific leg. @RequestID Request a composite timetable of all direct services from A to B. @RequestID Request service specific timetables (can be composite). @RequestID Request events at a stop of group of stops. @RequestID Search for services and timetable details. @RequestID Request a list of supported operators. @DataDate. @DataName (optional). Contains one or more responses. @RequestID Contains the points for the specified RequestID. @RequestID Contains the journeys for the specified request ID. @RequestID Contains journey leg details for the the specified RequestID. @RequestID Contains the timetable for the specified RequestID. @RequestID Contains the stop events for the specified RequestID @RequestID Contains the services for the specified RequestID. @RequestID Contains the operators for the specified RequestID. Date when the source database was last updated. Optional name of the source database. The version of the schema that the JourneyWeb instance document was written against. This attribute conforms with e-GIF guidance. Type for JourneyWeb Points Request. The locality for which points are being requested. @Precision (optional) A co-ordinate for which nearby points should be returned. The range of the search is undefined. Type for JourneyWeb Journeys Request. The places used for the origin. Via place for passing only (no stopover times). The via only has to go via one of these places e.g. if this defined all the bays in a bus station the journey only has to go via one of the bays. Identifier of a place The name of the via to be used in the results. Allows results to be given using the name that the user has selected instead of a name select from NaPTAN (particularly useful with multi-lingual places). Must be given when a geocode is used as the via. Not via places to avoid. The resulting journey must not stop at any of these points. The name of the not-via to be used in the results. Allows results to be given using the name that the user has selected instead of a name select from NaPTAN (particularly useful with multi-lingual places). Must be given when a geocode is used as the not via. The places used for the destination. Whether the request is an arrive-before or depart-after request. The number and extent of journeys to return. The requested journeys are returned from each origin place to any of the destination places. The requested journeys are returned from any origin place to each of the destination places. Type of search algorithm (default is default) Preferred walk speed (default normal). Maximum walking distance tolerated. Preferred interchange speed (default normal). Options restricting the available routes. Specifies if routes with limited accessibility interchanges should be requested. Defaults to no accessibility exclusions. Requests a journey without the specified accessibility hazard. @Exclude. default false: exclude specified values; true, include specified values. Which modes of transport to include in request. If omitted then all modes are to be included. @Exclude. default false: exclude specified values; true, include specified values. The operators to include/exclude from the calculation. If omitted then all operators may be included. Unique code of an operator to include or exclude. @Exclude. default false: exclude specified values; true, include specified values. The services to include/exclude from the calculation. If omitted all services may be included. Service to be included or excluded. Options controlling level of detail returned. Type for JourneyWeb LegDetails Request. Legs for which details are requested. Identifies a leg for which details are to be returned. Options controlling level of detail returned. Type for JourneyWeb StopTimetable Request. Start place for the timetable request. A choice of places for the origin. The name of the origin to be shown in the timetable description. Allows results to be given using the name that the user has selected instead of a name select from NaPTAN (particularly useful with multi-lingual places). Must be given when a geocode is used as the origin. Destination point for timetable. A choice of places for the destination. The name of the destination to be shown in the timetable description. Allows results to be given using the name that the user has selected instead of a name select from NaPTAN (particularly useful with multi-lingual places). Must be given when a geocode is used as the destination. @Exclude. default false: exclude specified values; true, include specified values. Modes of transport for which timetables are to be returned. If omitted then all modes are to be included. @Exclude. default false: exclude specified values; true, include specified values.The operators to include/exclude from the calculation. If omitted then all operators are possible. The unique operator code when available. @Exclude. default false: exclude specified values; true, include specified values. The services to include/exclude from the calculation. If omitted all services are possible. A transport service run by an operator. Type for JourneyWeb ServiceTimetable Request. The unique description of each service that should be output in the composite timetable. The minimum required to uniquely identify a service. A private service ID that only has meaning to the remote server. Only needed when PrivateID does not give a unique service. Whether to include a URL to a schematic map of the service (if available). Type for JourneyWeb StopEvents Request. The stops that events are requested for. Time and date of first event (default now). Return arrival, departures or all (default all) The number and extent of events to return. default 24 hours. Whether to return only the first event of each service. (default false, i.e return all). Which types of intermediate stops are to be returned, 'all,' 'before', 'leg', etc (default none). Whether real-time information should be returned (default false, i.e. omit real-time data). @Exclude. default false: exclude specified modes. true, include specified modes. The transport modes for which stop events are to be returned. If omitted, include all modes. Specifies criteria for omitting services from the response. @Exclude. default false: exclude specified values; true, include specified values. The operators to include/exclude from the calculation. If omitted all operators are to be included. @Actual. default false: exclude specified values; true, include specified values.Only return services that have previously passed one to these points (doesn't have to be the service origin unless actual = true). If omitted, do not filter by origin. NaPTAN stop identifier of an origin. @Actual. default false: exclude specified values; true, include specified values. Only return services that will go on to pass one to these points (doesn't have to be the service destination unless actual = true). If omitted, do not filter by destination. NaPTAN stop identifier of a destination @Exclude. default false: exclude specified values; true, include specified values. The services to include/exclude from the calculation. If omitted include all services. Service to be included or excluded. Type for JourneyWeb Services Request. Identifies the operator for which services are to be returned. @BeginWith default false; use whole service number. true, all services that begin with the specified string will be returned e.g. begin with 1 would return services 1, 11, 105, X1, X15, etc Identifies service to be returned. The direction of services which are to be returned. @Exclude. default false: exclude specified modes. true, include specified modes. The transport modes for which services are to be returned. If omitted, include all modes. Type for JourneyWeb Operators Request. @Exclude. default false: exclude specified modes. true, include specified modes. The transport modes for which operators are to be returned. If omitted, include operators for all modes. Type for JourneyWeb Points Response. Unordered set of points. @TimingInformationPoint (optional). true. point is a timing point. false not a timing point, absent: unknown. @LocalityCentre (optional). true point is a locality centre. false not a locality centre, absent: unknown. If the request was being made using a coordinate and the distance to the stop has been calculated using a better method than crow-flies then this is the calculated distance to the point. Type for JourneyWeb Journeys Response. Contains the journeys that satisfied the request. If omitted then no journeys could be returned. An individual journey fulfilling the constraints of the request. Information about the journey returned. E.g. 'Does not satisfy accessibility requirements'. The legs that make up the complete journey. In sequence of use. Place holder for future development of fares. Defined at the journey level to accommodate fares that cover more than one leg of the journey. Unique identifier of a request. Type for JourneyWeb LegDetails Response. Contains an unordered list of the legs that were requested, to the appropriate level of detail. Unique identifier of a request. Type for JourneyWeb StopTimetable Response. A service timetable. The title to use for the timetable. For stop to stop timetables it should include the stop names, e.g. London to Edinburgh. The first date for which timetable has been generated. The days for which this timetable has been generated. The last date for which this timetable has been generated. Should only be used for pre-generated timetables, timetables generated on the fly should have a LastDate. The stops that are shown in the first column of the timetable. The size of this list defines the number of rows. The stops must be in the order that they are to be displayed in. The same stop can be repeated (circular routes, and composite timetables with different stopping patterns). @Activity @StopType @Num The columns on the timetable. The must be in the order they are to be displayed. Contains all details of the column. Service details are included her to support composite timetables e.g. stop to stop timetables. Reference to service details for this column. Days of operation if different to those specified in the service details. The abbreviation of a note which is defined later in the schema. Notes if abbreviations are not being used. @TimingInformationPoint (optional) @Activity (optional). Used for a column of times. Must be one for each stop. Activity only needed if row Activity is Mixed. Used for a column that includes text only e.g. frequency column. Must be a label for every stop. @Ref. Details for the service references used in the columns. General timetable notes or the notes to go with abbreviations used in the columns. If left blank then the note represents a general timetable note. The note that goes with the abbreviation. Type for JourneyWeb StopEvents Response. The arrivals or departures at a stop. An arrival or departure at a stop. @TimingInformationPoint. The origin of this vehicle. Only omitted if the event occurs at the origin. The timetabled departure time from the origin. If frequency based service then leave out - frequency is defined in stop below. @TimingInformationPoint The stops between the origin and the requested stop. Only returned if requested. @TimingInformationPoint The stop where the event occurs. @TimingInformationPoint The stops between the requested stop and the destination. Only returned if requested. @TimingInformationPoint The destination of this vehicle. Only omitted if the event occurs at the destination. The timetabled arrival time at the destination. Reference to service details for this event @Ref. Details for the service references used in the stop events. Type for JourneyWeb ServiceTimetable Response. A collection of services meeting the request criteria. Description of a transport service. Type for JourneyWeb Operators Response. Transport service operators Transport service operator A code Identifying Transport Service Operator The customer facing name of the operator. Transport Mode of Service provided by operator Groups parameters controlling how the timetable should be returned. The date for which the timetable is to be generated. If true then the timetable that spans the specified date is returned. If false then the timetable for only the specified day is returned. Whether to only include timing information points in the response. The earliest departure time to include in the output. The latest departure time to include in the output. The number of the first column to return. The maximum number of columns to return. Groups elements describing a service's frequency of operation. The maximum duration for this leg of the journey. The scheduled time gap between departures for a frequency-based service. Minimum and maximum time gaps can be specified as attributes. Groups elements describing a service's duration. The window of opportunity that the traveller has to perform this leg of the journey. The typical duration of this leg of the journey. Groups arrival and departure times for an event at a stop. The time that the vehicle is timetabled to arrive. The time that the vehicle is timetabled to depart. Only to be used when arrival and departure time are the same. The scheduled time gap between departures for a frequency-based service. Minimum and maximum time gaps can be specified as attributes. Groups rea-time and scheduled departure times for an origin. Groups timetabled and real-time times at stop where the journey leg starts. Only to be used when arrival and departure time are the same. Groups the vehicle at stop time elements. Scheduled time of arrival of vehicle at stop. Scheduled time of departure of vehicle from stop. Only to be used when arrival and departure time are the same. Groups timetabled and real-time times at stop where the journey leg ends. Only to be used when arrival and departure time are the same. Groups the arrival times at the destination. Groups real-time arrival times at stop. Estimated time of arrival of vehicle at stop. Actual time of arrival of vehicle at stop. Groups real-time departure times at stop. Estimated time of departure of vehicle from stop. Actual time of departure of vehicle from stop. Empty type used to enforce empty content of indicator elements (such as those used in DaysOfOperationStructure). Distance (metres) as defined by http://www.ordnancesurvey.co.uk/xml/resource/units.xml#metres A restriction of W3C XML Schema's duration datatype that only allows durations to be measured in days, hours, minutes and seconds. This permits a total ordering of values. Transport Operator identifier code type. Type for stop identifiers. Short code for region e.g. S (Scotland) SE (South East). Direction taken (for example, eastbound, inbound, anti-clockwise). Identifier type for a NaPTAN stop Identifier type for a NaPTAN locality.. Types of journey planning optimisation algorithms supported by JourneyWeb. Allowed values for stops. Natural Languages supported by JourneyWeb. English. Welsh. Irish. Scots Gaelic. Quantised speed levels supported by JourneyWeb. Obstacles to accessibility. For example, slippery surfaces or grids. Kinds of vertical movement. Allowed values for Arrival before or Departure after journey planning constraint Allowed values for Arrival before or Departure after stop event constraint. Allowed values for timetable row activities. Mapping systems that the client may use. Ordnance Survey MasterMap Topographical ID. Ordnance Survey ROADS (previously OSCAR hence the O) Database Reference. NavTech mapping reference. Mentz Datenverarbeitung GmbH mapping reference http://www.mentzdv.de . Allows the client to request no mapping system information to be returned. Different grid systems (e.g. UK OS, Irish OS) that can be used to express Eastings and Northings. Ordnance Survey UK grid with origin at bottom left of Sheet SV. Ordnance Survey Irish grid with origin at bottom left of Grid V. Levels of precision for geocodes. Available types of features for describing walk legs. The start point of the leg. The end point of the leg. A bend in the track that merits attention (without a junction). Cross over the road. Traversing over a bridge. Either a point at which another road is taken, or a side road that is passed along the way. Denotes a change of road name when there is no junction. Going through a subway. A named landmark that can be seen from the track. The name should be provided in the Feature Description. Available directions to turn from a feature point. Modes of transport applicable to timetabled public transport. Modes of transport applicable to private and non-timetabled transport. Union of vehicle and continuous modes. Determines the types of interchange nodes in terms of their transport mode. Allowed values for stop activities. Allowed values for stop types. Co-ordinate type that supports easting and northing. Specifies the grid system being used. e.g. UKOS or IrishOS. OS 1 metre - 6 digits. OS 1 metre - 6/7 digits. Based on the LineString element from GML 2.1.2, but using JourneyWeb coordinate representations. @Precision, @GeocodeId. A point on a map. Id may refer to a previously defined point. Either a rendered map or a sequence of points that can be rendered by the client. Set of physical points which describe this segment. This must include the beginning and end of the segment. URL of a custom map rendered by the journey planning system. @MappingSystem. Map element IDs (e.g. OSODRs or TOIDs) can be passed separately to ease the mapping process for those systems that support them. This enumeration should include all mapping systems used by JourneyWeb clients and suppliers. The elements that identify a service. Code identifying transport operator. The customer facing service number. Define but leave blank where there isn't one e.g. most rail services. Direction of travel. Not well defined.! The minimum required to identify a service in a request. Unique code of operator. Identifier of service. Direction in which service runs. The minimum required to uniquely identify a service. Unique code of operator. Identifier of service. Direction in which service runs. Information that can be returned about a service in a response. Transport mode of service, e.g. bus Description of a service used in a Continuous Leg. The mode of the service. Shared elements between the ServiceResponseStructure and the ContinuousLegServiceStructure. The customer facing name of the operator. The description of the service. Date that service commences. The days of the week for which this trip is valid at this time. The last day that this trips timetable is valid. The timetable does not have a specified end date. The name displayed on the front of this vehicle. Link to a timetable for this leg of the journey. The scheduled time gap between departures for a frequency-based service. Minimum and maximum time gaps can also be specified. The scheduled time gap between departures for a frequency-based service. The minimum time gap between departures for a frequency-based service. The maximum time gap between departures for a frequency-based service. Options controlling level of detail returned. Which types of intermediate stops are to be returned (default none). all, before leg, etc. Whether to include detailed track information for the legs for which track data is available (default false). Whether to include textual instructions for legs using particular modes. Default is to omit all instructions. Note that including instructions for a particular mode will also include track data for that mode (even if IncludeTracks has been set to false). Specifies a mode for which leg instructions should be returned. Whether to include detailed interchange information in response (default false). Whether real-time information be returned (default false). The mapping system which the client understands e.g. TOID, OSODR, NavTech, MDV, none. Defaults to none - i.e. no mapping system references are to be returned. @Exclude (optional). The modes to include/exclude from the calculation. If omitted then all modes are used. A method of transportation such as bus, rail, etc. Type for specifying place references on requests ID of a NaPTAN node. @Precision NPTG identifier of locality Type for specifying additional request general constraints. The number of journeys to return after the departure time or before the arrival time. An interval after a departure time or before an arrival time for which journeys should be returned. Used to limit the number of journeys returned for an interval. e.g. Get the first 3 journeys in the next 6 hours. An example use of this is to get the first 3 journeys during an off-peak period i.e. stop the search before the peak period starts. Maximum number of journeys An interval after a departure time or before an arrival time for which journeys should be returned. Minimum number of journeys to return. If greater than zero this will extend the interval if not enough journeys have been found. Default zero. The maximum interval to search when extending the interval to find a minimum number of journeys to return. The default of 24 hours is not included in the schema due to validation problems with Xerces. Type for specifying origin and destination places on requests. The individual places that make up the origin or destination. In most cases these are a choice of start or end places (see Range). Identifier(s) of the place. Normally one of the following. Multiple NaPTAN codes may be used. The arrive or depart time and date for this place. Details of the calculation so far from the origin or destination. Can be used to implement the maxChanges algorithm, to allow the journey to continue on the same vehicle, etc. For depart after requests this is the departure time at the origin. For arrive by requests this is the arrival time at the destination. The last service used in the calculation. Used in conjunction with JourneyTime to allow the same vehicle to be used. The walk distance so far in metres. The name of the origin/destination to be used in the results. Allows results to be given using the name that the user has selected instead of a name select from NaPTAN (particularly useful with multi-lingual places). Must be given when a geocode is used as the origin/destination. @TimingInformationPoint (optional) Represents a place in a response. A meaningful name for the place that will be given to the end user. If a GivenName was input in the request it should be returned here. This will usually contain more than the NaPTAN name e.g. Locality and NaPTAN name - Epsom: High Street ID of a NaPTAN node @Precision (optional) default 1 km The coordinate of the NaPTAN stop - can be used for rudimentary map displays. @Precision (optional) default 1km A point on a map. Additional bay information that is not implied by a NaPTAN ID e.g. rail platform. Type for Days of operation. Type for URL to timetable. A URL which can be used to obtain a pre-rendered timetable - PDF, HTML, etc. A URL which can be used to obtain a pre-rendered schematic map of the service - PDF, HTML, etc. A private identifier to unique identify a timetable (may represent both directions with a single ID - in which case direction will be defined as well). This can be used ServiceTimetableRequest to obtain the timetable data. Used if the PrivateID doesn't include direction Indicates if matrix timetable data can be requested for this timetable. A collection of legs. A leg that runs to a timetabled time. A leg that runs to a given frequency. A leg that doesn't run to any type of schedule, e.g. walking, cycling A leg that describes an interchange. Can occur as end leg as well as within journey (e.g. Waterloo station to TCR - would need to interchange to underground first). Geospatial representation of a leg for mapping and instructional purposes. @TransXChangeSegmentID:an optional reference to the operator's TransXChange ID for the segment. A track segment describes a section of the geospatial representation of a leg. The choice of segments subdividing a leg is left up to the server. Information to create a visual map. @MappingSystem A mapping system reference (e.g. TOID, OSODR, NavTech, MDV) value which the requesting client has asked for. This contains the information necessary to describe a track segment textually in a step by step fashion. Optional textual description of segment. May correspond directly to features or may be a customised replacement (e.g. for commonly used segments). @GeocodeRef Represents a physical obstacle in the route e.g. a crossing. The first feature point should be the start point of the leg (the leg board point). Each feature contains directions to the next feature. An enumeration of the different types of features. Which way you would turn from this feature point. The compass bearing which you should take directly from this feature point. The name of the road or path following this feature. The number of the road following this feature e.g. A1. Provides the distance to the next feature point, or to the leg alight point for the last feature point. Provides a description of the feature. Refers to a geocode in the mapping information for the track segment. Identifies the segment according to its TransXChange ID. An abstract base type for non-interchange legs. Information about the leg returned. E.g. Intermediate stops not available. @TimingInformationPoint (optional) The origin place. Only omitted if the board place is the origin. @TimingInformationPoint (optional) Returned if IncludeIntermediateStops is set to 'all'. @TimingInformationPoint (optional) true if this is the requested via point. @TimingInformationPoint (optional). Returned if IncludeIntermediateStops is set to 'all' or 'leg', or this is the via point i.e. pass = true. true if this is the requested via point @TimingInformationPoint (optional). true if this is the requested via point. @TimingInformationPoint (optional) Returned if IncludeIntermediateStops is set to 'all'. @TimingInformationPoint (optional). The destination place. Only omitted if the alight place is the destination. @TotalDistance Geospatial representation of the leg for mapping and instructional purposes. Any notes about the vehicle or walk. Identifies the leg for future reference in any LegDetailsRequests. Type for a leg that runs to a schedule. Type for a leg that runs a frequency based service. Times for the complete trip of the vehicle. Times for the part of the journey the traveller will make. LegBoard and LegAlight should be used to describe walk, etc. ServiceOrigin and ServiceDestination should only be used for DRT. Description of the service (mostly optional as could be used to describe a walk leg). Structure of an interchange leg. Start point of Leg. Equivalent to the "LegBoard" for this leg (but since there is no vehicle involved there can be no boarding). End point of Leg. Equivalent to the "LegAlight" for this leg (but since there is no vehicle involved there can be no alighting). Describes the interchange in terms of a sequence of pairs of nodes and links with accessibility and duration. A point within an interchange. Either a point of access to transport, such as a bay, or an intermediate point between other nodes. A possible path between two interchange nodes. The final node in the interchange path - should correspond to the LegDestination. Optional mapping information for displaying interchange legs. Schematics are hyperlink references to hand-crafted schematic map images. A hyperlink to the schematic map. Maps should be in a web compatible image format (e.g. JPEG, GIF) that can be embedded in a web page or a PDF. @GeocodeRef A node in the interchange model. Each node has a type indicating its primary function (for example, a rail platform would have a type of "rail") Determines the types of interchange nodes in terms of their transport mode. Name or brief description of node. For example, "Waterloo Main Concourse". If the node corresponds to a NaPTAN node then the NaPTAN ID should be included here. Refers to a geocode in the optional mapping information provided as part of the Interchange Leg. If mapping information is provided then this reference is required. A link in the interchange model. Links have a duration and optional accessibility hazards. How long it takes to traverse the link, assuming the specified walk speed. A description of the link. Information on any limits on accessibility on the link. @ChangeOfLevel whether the link goes up or down. The nature of the accessibility constraint. One of a fixed list of defined values.