Databases containing personal information are acquiring ever-greater significance, both in the private and business realms.  Thus, for example, it is known that companies access address databases and then send their advertising to persons stored in these databases in order to acquire new customers in this manner.  Consequently, owing to the financial significance of such databases, it has now become common practice to buy and sell the contents of such databases, so as to also make the stored personal information available to other companies in exchange for payment.  In this context, the value of such a database or of its contents depends to a decisive extent on the scope of the stored personal information and on how up-to-date this information is. 
It is known nowadays that such databases or their contents are compiled essentially manually.  To this end, potential customers are requested, for instance, through the modality of sweepstakes, to provide their addresses and other items of personal information.  By the same token, information can be accessed that is typically available at mail-order companies, provided that the customers stored there have not explicitly prohibited their data from being passed on to others. 
In addition to the above-mentioned databases essentially containing information about potential customers or recipients of advertising, another typical area of application for databases containing personal information is, for example, an address database and/or an appointment database.  Nowadays, many people keep databases of the above-mentioned type for their business activities and sometimes also for their private sphere listing the contacts these persons use such as, for instance, business partners, friends, physicians, attorneys, public addresses, etc. 
Also in the case of the latter databases, the problem of keeping the databases updated arises, for instance, when persons whose information is stored in such a database have moved elsewhere, thus changing their addresses, or else the person has contact data that has changed in the meantime for other reasons such as changed phone numbers, e-mail addresses, mailing addresses and the like.