Ranking distributed uncertain database systems: Discussion and analysis

Large databases with uncertainty became more common in many applications. Ranking queries are essential tools to process these databases and return only the most relevant answers of a query, based on a scoring function. Many approaches were proposed to study and analyze the problem of efficiently answering such ranking queries. Managing distributed uncertain database is also an important issue. In fact ranking queries in such systems are an open challenge. The main objective of this paper is to discuss ranking in distributed uncertain database along with its issued problems. Starting with uncertain data representation, query processing and query types in such systems are discussed along with their challenges and open research area. Top-k query is presented with its properties, as a ranking technique in uncertain data environment, mentioning distributed top-k and distributed ranking problems.