With the development of global networking, invention of WWW, and proliferation of Internet-enabled computer hardware and software into homes and pockets, a huge customer base has been created for electronic commerce. It is rapidly expanding in USA and Europe and Japan are following the trend. So far, the development of E-commerce has happened in a rather unregulated way especially in USA, whereas in Europe the European Commission has been developing a regulatory basis mainly in form of directives. Currently (12/1999) they have not yet all been accepted and a major restructuring of the regulatory framework has also been planned. Another technological development is the rapid growth of mobile computing, especially through WAP technology, which makes also mobile E-commerce possible.

In this article we review the need of a transaction model and the corresponding transactional mechanism and its usefulness for E-commerce in general and for mobile E-commerce in particular. We tackle the issue both theoretically and empirically. In the theoretical part we review some of the earlier work, and discuss especially money atomicity, goods atomicity and certified delivery. The empirical part consists of trials at three E-commerce sites, two in Finland and one in USA and reveal important differences in the structure of E-commerce transactions in different cases. These must be taken into consideration when transactional support is developed further.

Using the emerging technology both customer and merchant can now become mobile, although it is more probable that a customer is mobile but a merchant stationary. Communication autonomy and other autonomy aspects and miniature size of the terminals aggravate the problems of achieving the various levels of atomicity. Security, privacy, authentication, and authorization are of paramount importance in an open network environment. One important conclusion is that the transactional mechanism must be closely related with these aspects and that the main goal of using the transactional mechanism is actually to support security, privacy, authentication and authorization -- and vice versa.