“…A dataspace system copes with the problem of integrating a variety of data based on their structures and semantics such as structured, semi-structured, and unstructured data, and returns the best-effort or approximate answer to its users [16,17,30]. The existing works on query processing and query answering paid attention to return top-k answers to the users in the area of dataspace system [6,10,15,18,29,40,42,4,26,22,38,19,34,39,37,33,41]. The motivation behind this work is to focus on "how is information important?"…”