9.1 Introduction

Classical relational database model and its extension of imprecision and uncertainty do not satisfy the need of modeling complex objects with imprecision and uncertainty. So many researches have been concentrated on the development of some database models to deal with complex objects and uncertain data together. In (Yazici et al., 1999), an extended nested relational data model (also known as an NF ² data model) was introduced for representing and manipulating complex and uncertain data in databases and the extended algebra and the extended SQL-like query language were hereby defined. Also physical data representation of the model and the core operations that the model provides were also introduced in (Yazici et al., 1999). It should be pointed out that, being the extension of relational data model, NF ² data model is able to handle complex-valued attributes and may be better suited to some complex applications such as office automation systems, information retrieval systems and expert database systems (Yazici et al., 1999). But it is difficult for NF ² data model to represent complex relationships among objects and attributes. Some advanced abstracts in data modeling (e.g., class hierarchy, inheritance, superclass/subclass, and encapsulation) are not supported by NF ² data model, which are needed by many real applications. Therefore, in order to model uncertain data and complex-valued attributes as well as complex relationships among objects, current efforts have being focused on conceptual data models and object-oriented databases (OODB) with imprecise and uncertain information.

Regarding modeling...