Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1997-01-31
2001-05-01
Amsbury, Wayne (Department: 2777)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000
Reexamination Certificate
active
06226646
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a storage medium carrying data relating to a plurality of geographical locations, which data comprise for each of the geographical locations a data structure with one or more attribute values.
The invention further relates to a system for reading data relating to a plurality of geographical locations from a storage medium, the data for each of the geographical locations comprising a location code and a data structure with one or more attribute values, which system comprises a read module for reading a given data structure associated with a given location code on the basis of correspondence of a given code to said location code.
The invention further relates to a TMC receiver for receiving traffic messages.
The invention further relates to a method of storing data relating to two or more geographical locations on a storage medium, a data structure with one or more attribute values being stored for each of the geographical locations.
The invention further relates to a system for storing data relating to two or more geographical locations on a storage medium, which system comprises a write module for storing for each of the geographical locations a data structure with one or more attribute values.
The storage and the processing of said data are known from the document “Location Referencing Rules For RDS-TMC”, European Road Transport Telematics Implementation Co-ordination Organisation, Task Force on Geographical Location Referencing, CORD Project V 2056, Deliverable No D010, August 995. This document gives a number of rules concerning the specification of geographical locations for use in traffic messages. One application of such traffic messages is the presentation of traffic information to drivers of vehicles. A traffic message is then transmitted from a central station and received by a receiver in the vehicle. Such a receiver is referred to as a Traffic Message Channel (TMC) receiver. This receiver converts the traffic message into information for the driver and reproduces this information via a display screen or via a loudspeaker. The data specifying a geographical location is stored on a local storage medium in a system in the receiver. A traffic message generally includes only a reference to a geographical location and upon reception of the traffic message the system in the vehicle retrieves the data relating to the geographical location from the local storage medium. Page 22 of the reference specifies a number of location types. For each of said types it is defined which attributes, i.e. what types of data, form the specification. Some attributes are mandatory and some are optional. In addition to said attributes, it is further possible to include extra attributes in order to adapt the specification of geographical locations to a given application, see for example pages 27 and 28 of the reference. Annex A
1
of the reference contains a more comprehensive list of types of geographical locations.
The known system, which utilizes information about geographical locations in the above manner, carries the data relating to a multitude of geographical locations on a local storage medium. For each geographical location space for any possible attribute of a geographical location has been reserved on the storage medium. This results in a record having a fixed layout in fields which store values of the attributes. The system knows this layout and consequently knows the location in the record where the value of a given attribute is stored, for example the name or the number of a road, and can process this information. A drawback of the known storage medium is that some of the fields reserved in the records on the storage medium remain unused because no values exist for all the possible attributes of each geographical location. A further drawback of the known storage medium is that a future extension of attributes of a geographical location makes it necessary for the system reading the storage medium to be immediately adapted to the extension. A new version of the storage medium storing records with a new field for a new attribute cannot be read by the current version of the system because the layout of the record has been changed.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a storage medium of the type defined in the opening paragraph, on which the data can be stored in a more efficient and more flexible manner than on the known storage medium. To this end, the storage medium in accordance with the invention is characterized in that the data for a first one of the geographical locations comprise a first structure description, which describes a layout of the data structure associated with the first geographical location and for a second one of the geographical locations comprise a second structure description, which second structure description differs from the first structure description and describes a layout of the data structure which is associated with the second geographical location and which differs from the first data structure. For a given geographical location the values of a number of attributes are stored in the data structure on the storage medium. Which attributes these are and how large the required space for the value of each of the attributes in the data structure is, is specified in the relevant structure description. For different geographical locations with values for different attributes different structure descriptions are stored on the storage medium. If for different geographical locations values for the same attributes are present on the storage medium, the same structure description can be used for both locations. As a result of the use of the structure description, it is no longer necessary to reserve in advance space for a value of any possible attribute for a geographical location. An advantage of the storage medium in accordance with the invention is that it is adequate to store only the data structure with the currently existing values of the attributes and a structure description which specifies the data structure for the relevant geographical location. The number of structure descriptions required is substantially smaller than the number of different geographical locations for which data have been stored, because for many locations a similar combination of attributes is used. A further advantage of the storage medium in accordance with the invention is that the actual layout of the data structure of the data of a geographical location is stored with the data themselves and need not be known in advance in the system which is to read the data. For a given geographical location it is determined by means of a structure description for which attributes the storage medium stores a value and how the layout is. When a subsequent version of the storage medium with a value for a new attribute for the given geographical location is issued, the structure description on the new version of the storage medium will describe this new layout. As a result, the new version can be read and processed in the same way as the current version. For the same reason a newer version of the system, adapted to read the storage medium with the new attribute in the data structure, is readily capable of also reading the old version of the storage medium.
An embodiment of the storage medium in accordance with the invention is characterized in that the data for each of the geographical locations comprise a location index record, which record comprises a first reference to the structure description corresponding to the relevant geographical location and a second reference to the data structure associated with the relevant geographical location. Owing to the location index records the data of the relevant geographical location can be located more easily. The location index records are short, thus enabling the location index record corresponding to the desired geographical location to be found in a simple and rapid manner. Subsequently, on the basis of the first reference, the structure description is
Amsbury Wayne
Lewis Cheryl
Mannesmann VDO AG
Mayer Brown & Platt
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