We propose and investigate a semantics for "peer data exchange systems" where different peers are related by data exchange constraints and trust relationships. These two elements plus the data at the peers' sites and their local integrity constraints are made compatible via a semantics that characterizes sets of "solution instances" for the peers. They are the intended -possibly virtual- instances for a peer that are obtained through a data repair semantics that we introduce and investigate. The semantically correct answers from a peer to a query, the so-called "peer consistent answers", are defined as those answers that are invariant under all its different solution instances. We show that solution instances can be specified as the models of logic programs with a stable model semantics. The repair semantics is based on null values as used in SQL databases, and is also of independent interest for repairs of single databases with respect to integrity constraints.

本文提出并研究了一种语义，用于描述'点对点数据交换系统'，其中不同的点通过数据交换约束和信任关系相互关联。借助我们引入和研究的数据修复语义，将这两个元素与点站点的数据和本地完整性约束相兼容。通过逻辑程序的稳定模型语义指定解决方案实例，据此演示了逻辑程序可以用于指定解决方案实例等问题。此外，还介绍了基于SQL数据库中使用的空值的修复语义，并且还可用于对单个数据库进行完整性约束的修复，定义了称为'点一致答案'的向查询的正确答案。

点对点数据交换系统中的一致性和信任