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：存在约束是在关系数据模型中定义的，但遗憾的是，除其特例NOT NULL外，没有任何关系数据库管理系统提供这些约束。我们的（基础）数学数据模型将其扩展到函数积，并引入了与之对偶的非存在约束。基于这两种数据模型的智能数据与知识库管理系统原型MatBase不仅提供存在约束和非存在约束，还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。