Gradation: A pay-as-you-go style hybrid query language for structured and text data

There is an increasing number of Web data which consist of text and structured data, such as the combination of Wikipedia pages and DBpedia data. To issue queries to such data, we must choose one of the followings: (1) submit keyword queries against textual data part, or (2) submit structured queries in structured query languages like SPARQL, against structured data part. Keyword queries are easy for casual users to write, but they do not have expressive powers enough to fulfill the user’s information needs. On the other hand, structured queries are more expressive than keyword queries, but are not easy for casual users to write. This paper proposes a hybrid query language that seamlessly integrates the two types of queries, allowing us to write queries in a “pay-as-you-go” fashion.published or submitted for publicationis peer reviewe