PD ISO/TR 21707:2008

This Technical Report specifies a set of standard terminology for defining the quality of data being exchanged between data suppliers and data consumers in the ITS domain. This applies to Traffic and Travel Information Services and Traffic Management and Control Systems, specifically where open interfaces exist between systems. It may of course be applicable for other types of interfaces, including internal interfaces, but this Technical Report is aimed solely at open interfaces between systems.

This Technical Report identifies a set of parameters or meta-data such as accuracy, precision and timeliness, which can give a measure of the quality of the data exchanged and the overall service on an interface. Data quality is applicable to interfaces between any data supplier and data consumer, but is vitally important on open interfaces. It includes the quality of the service as a whole or any component part of the service that a supplying or publishing system can provide. For instance, this may give a measure of the availability and reliability of the data service in terms of uptime against downtime and the responsiveness of the service, or it may give a measure of the precision and accuracy of individual attributes in the published data.

In the majority of ITS applications, data is routinely exchanged between disparate systems. Where this data is being exchanged on a closed circuit between known senders and recipients, the parties concerned need to understand the quality of the data being exchanged and any resultant restrictions on its subsequent use by the recipient. In most cases, this is dealt with on a case-by-case basis and all parties to the agreement to exchange data will understand the quality parameters and restrictions.

However, transport and travel information is frequently being provided now via interfaces onto open networks for use by external users and it may not always be known from where this data has originated or for what purposes it is suitable. In these circumstances, a stated quality of the data becomes important and it is critical for users to understand the quality parameters so that accurate information can be derived from the data by itself or in combination with data from other sources.

Data quality meta-data includes the usual range of parameters normally associated with the measurement of quality such as accuracy, precision and timeliness of the data. However, there are other important quality meta-data such as ownership of the data. Ownership is important in many applications, and data suppliers may wish to restrict the usage of their data to certain classes of users. Measures of data quality may also be important in determining the relative monetary value of data in a commercial situation and so it is important that there is a common understanding of these measures.

It should be noted that, in the context of this Technical Report, data may be taken to be either raw data as initially collected, or as processed data, both of which may be made available via an interface to data consumers. The data consumer may be internal or external to the organization which is making the data available. Additionally, the data may be derived from real time data (e.g. live traffic event data, traffic measurement data or live camera images) or may be static data which has been derived and validated off-line (e.g. a location table defining a network). Measurements of data quality are of importance in all such cases.

This report is suitable for application to all open ITS interfaces in the Traffic and Travel Information Services domain and the Traffic Management and Control Systems domain.