Visualization of rule behaviour in active databases

Abstract

One of the characteristics of database systems is the ability to efficiently handle large amounts of information. This characteristic must apply also when rules are introduced into database systems, resulting in so-called active database systems. Hence, active database systems need to manage both a large amount of data and many rules. One of the problems with large sets of rules is the complexity of interaction between rules. A rule that is perfectly workable by itself may in the interaction with other rules produce serious malfunctions. To prevent such situations, a rule debug- ger is needed, preferably a visual one. In this paper we introduce Adela, a rule visualization tool suitable for the rela- tional data model. We introduce a multilevel rule concept, which is important when, for example, rule visualization tools need to display how rules are related to the data model and the data instances. Three different levels within the multilevel rule concept are provided: model level, rule level, and instance level. An event/rule trace tree is introduced to display: i) the context in which rules are fired, and ii) the execution states of rules. A data trace is introduced in order to display what is hap- pening to data instances when they are manipulated by rules. We also address issues such as scalability of rule visualization tools, and on-line rule visualization tools, which in real time show what is happening in active databases.