第946页 Chapter 22 Object-Based Databases

1. object-oriented database system
2. object-relational mapping

这两个概念虽然第一次接触。但是的确碰到过相关的应用。不知道结构式的储存是不是属于其中的一种情况。
As database systems were applied to a wider range of applications, such as computer-aided design and geographical information systems, limitations imposed by the relational model emerged as an obstacle. The solution was the introduction of object-based databases, which allow one to deal with complex data types.
Complex application domains require correspondingly complex data types, such as nested record structures,multivalued attributes, and inheritance,which are supported by traditional programming languages.Such features are in fact supported in the E-R and
extended E-R notations, but had to be translated to simpler SQL data types.
Differences between the type system of the database and the typesystem of the programming language make data storage and retrieval more complicated, and need to be minimized.
We then address the issue of supporting persistence for data that is in the native type system of an object-oriented programming language. Two approaches are used in practice:

1. Build an object-oriented database system, that is, a database system that natively supports an object-oriented type system, and allows direct access to data from an object-oriented programming language using the native type system of the language.

2. Automatically convert data from the native type system of the programming language to a relational representation, and vice versa. Data conversion is specified using an object-relational mapping.

We provide a brief introduction to both these approaches. Finally, we outline situations in which the object-relational approach is better than the object-oriented approach, and vice versa, and mention criteria for choosing between them.