On-the-fly data integration, i.e. at query time, happens mostly in tightly coupled, homogeneous environments where the partitioning of the data can be controlled or is known in advance. During the process of data fusion, the information is homogenized and data inconsistencies are hidden from the application. Beyond this, we propose in this paper the Nexus metadata model and a processing approach that support on-the-fly data integration in a loosely coupled federation of autonomous data providers, thereby advancing the status quo in terms of flexibility and expressive power. It is able to represent data and schema inconsistencies like multi-valued attributes and multi-typed objects. In an open environment, this best suites the application needs where the data processing infrastructure is not able to decide which attribute value is correct. The Nexus metadata model provides the foundation for integration schemata that are specific to a given application domain. The corresponding processing model provides four complementary query semantics in order to account for the subtleties of multi-valued and missing attributes. In this paper we show that this query semantics is sound, easy to implement, and it builds upon existing query processing techniques. Thus the Nexus metadata model provides a unique level of flexibility for on-the-fly data integration.

中文翻译：

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一种基于模式的方法来实现动态数据集成

动态数据集成，即在查询时，主要发生在紧密耦合的同构环境中，其中数据的分区可以被控制或预先知道。在数据融合的过程中，信息被同质化，数据的不一致对应用程序来说是隐藏的。除此之外，我们在本文中提出了 Nexus 元数据模型和一种处理方法，支持在松散耦合的自治数据提供者联盟中进行动态数据集成，从而在灵活性和表达能力方面提升现状。它能够表示数据和模式的不一致，例如多值属性和多类型对象。在开放环境中，这最适合数据处理基础设施无法确定哪个属性值正确的应用程序需求。Nexus 元数据模型为特定于给定应用程序域的集成模式提供了基础。相应的处理模型提供了四种互补的查询语义，以解决多值和缺失属性的微妙之处。在本文中，我们展示了这种查询语义是合理的、易于实现的，并且它建立在现有的查询处理技术之上。因此，Nexus 元数据模型为动态数据集成提供了独特的灵活性。易于实现，它建立在现有的查询处理技术之上。因此，Nexus 元数据模型为动态数据集成提供了独特的灵活性。易于实现，它建立在现有的查询处理技术之上。因此，Nexus 元数据模型为动态数据集成提供了独特的灵活性。