Existence constraints were defined in the Relational Data Model, but, unfortunately, are not provided by any Relational Database Management System, except for their NOT NULL particular case. Our (Elementary) Mathematical Data Model extended them to function products and introduced their dual non-existence constraints. MatBase, an intelligent data and knowledge base management system prototype based on both these data models, not only provides existence and non-existence constraints, but also automatically generates code for their enforcement. This paper presents and discusses the algorithms used by MatBase to enforce these types of constraints.

翻译：存在性约束最初在关系数据模型中定义，但遗憾的是，除了其NOT NULL特例外，没有任何关系数据库管理系统提供此类约束。我们的（初等）数学数据模型将其扩展至函数乘积，并引入了其对偶的非存在性约束。MatBase是一个基于上述两种数据模型的智能数据与知识库管理系统原型，它不仅提供存在性与非存在性约束，还能自动生成强制执行这些约束的代码。本文介绍并讨论了MatBase用于强制执行此类约束的算法。