Digital tags: data with restricted accessibility for e-commerce applications

A digital tag is defined to be attached to objects and there are the following two kinds of major functions; (1) tags are only accessible through base objects and there are constraints which should be satisfied to access a tag, (2) tags can be used as paper tags in the real world. In many cases, it cannot exist without objects to be attached. For each object we can define a real or virtual world location such that the object can be accessed only from users close to it. In the real world the distance is defined to be real distance and in the virtual world it is defined to be, for example, the number of links to access the object to which the tag is attached. It can be used to simulate the real world constraints, since in the real world information available to a user will be changed by the location of the user and time-date. In this paper a definition of digital tags is given. Using digital tags we can realize e-commerce systems satisfying constraints currently realized by the real world. Although it is said that by e-commerce all price information is available to consumers and thus they can select the best sellers, apparently such a situation is not acceptable for most sellers and we believe realization of the current real-world constraints is important at least during the transition period. Since conventional database model is used as a basis, it is possible to remove some or all of real-world constraints and add artificial constraints. We have developed a prototype based on the idea using mobile computing systems, called a `SpaceTag´ system, where a space tag is a special case of a digital tag