DBMS support for time and totally ordered compound data types

摘要

Certain DBMSs support a small class of time-point and time-duration types. One limitation is that these types vary from one DBMS to another and a default finest time resolution is always considered, which is completely dependent on the commercial software. In practice however, there are applications in which types, other than those supported by a specific DBMS, need be used. As a consequence, applications have to be appropriately adapted or programmers have to write their own code. To overcome these problems, a set of primitive data types is identified in this paper and operations are formalized, by which arbitrary time-points of a hardware rather than software dependent resolution, can be defined by users. A set of composite numbers is also defined as another representation format for integers. It is shown that a time-duration type is actually only one of the many ways by which such a set can be interpreted. Generic operations are defined between time-ponts and time-duration types. The formalization is quite general and can be applied both to temporal databases, in which time plays a primary role and also to the definition by the user of new compound types of practical interest, in terms of others.