Enabling queries on relational data on the Web

虽然万维网为公众提供了有史以来最大和最异构的数据集之一，其查询能力仍然非常有限的关键字搜索。这降低了搜索的效率和可以探索或检索的信息的范围。更具体地说，当搜索不限于选择并且涉及对文档内容的连接和设置操作时，关键字搜索是不够的。例如，关键字搜索不适合查询关系，而Web包含大量的关系。此外，当搜索结果的粒度小于文档并且结果是满足某些条件的更精细的项或实体集合时，关键字搜索不是非常适用。

While the World Wide Web provides public access to one of the largest and most heterogeneous data collections ever created, its querying capabilities have remained very much limited to keyword search. This reduces the efficiency of the search and the scope of the information that can be explored or retrieved. More specifically, a keyword search is not sufficient when the search is not bounded to a selection and involves join and set operations over the contents of the documents. For instance, a keyword search is not appropriate for querying relationships, and the Web contains relationships galore. Also, a keyword search is not very applicable when the granularity of the search result is smaller than a document, and the result is a more refined set of items or entities that satisfy some conditions.