Research into Declarative, Object-Oriented Languages for Programming Data and Knowledge

关系查询语言，如SQL，是声明式编程的早期成功案例。然而，随着新的应用领域的发展，关系系统被发现存在不足。它们的局限性--与结构和语言有关--导致了数据库和演绎数据库。当数据的结构是众所周知的，并且数据访问路径和检索方法可以在系统开发时确定时，面向对象的数据库(简称O-O)是有效的。基于逻辑的演绎DBMS适用于定义不太明确的情况，即事先不知道将被询问的所有查询的情况。灵活性对于现代DBMS非常重要，尤其是当用户缺乏关于应用程序域结构的详细知识时。为此，传统上每当需要智能处理数据时都会使用基于逻辑的语言。另一方面，这种语言固有的平面数据结构不适合于许多科学应用、CAD/CAM设计、建模、敏捷制造过程等，其中数据具有复杂和已知的内部结构。

Relational query languages, such as SQL, were the early success stories of declarative programming. However, as new applications areas have developed, relational systems have been found wanting. Their limitations--both structural and language related--have led databases and deductive databases. Object-oriented databases (abbr., O-O) are effective when the structure of the data is well- known and the data access paths and retrieval methods can be determined at system development time. Deductive DBMS, based on logic, are appropriate in less well-defined situations; situations where one does not know before-hand all the queries that will be asked. Flexibility is extremely important for modern DBMS, especially when the user lacks detailed knowledge about the structure of the application domain. For this reason, logic-base languages have traditionally been used whenever intelligent processing of data was required. On the other hand, flat data structures inherent in such languages are ill-suited for many scientific applications, CAD/CAM design, modeling agile manufacturing processing, etc., where data has complex and known internal structure.