A spatial preference query ranks objects based on the qualities of features in their spatial neighborhood. For example, using a real estate agency database of flats for lease, a customer may want to rank the flats with respect to the appropriateness of their location, defined after aggregating the qualities of other features (e.g.,restaurants, cafes, hospital, market, etc.) within their spatial neighborhood. Such neighborhood concept can be specified by the user via different functions. It can bean explicit circular region within a given distance from the flat. Another intuitive definition is to assign higher weights to the features based on their proximity to the flat. In this paper, we formally define spatial preference queries and propose appropriate indexing techniques and search algorithms for them. Extensive evaluation of our methods on both real and synthetic data reveals that an optimized branch-and-bound solution is efficient and robust with respect to different parameters.
To our knowledge, there is no existing efficient solution for processing the Top-k Spatial preference query. Object ranking is a popular retrieval task in various applications. In relational databases, we rank tuples using an aggregate score function on their attribute values. For example, a real estate agency maintains a database that contains information of flats available for rent. A potential customer wishes to view the top-10 flats with the largest sizes and lowest prices. In this case,the score of each flat is expressed by the sum of two qualities: size and price, after normalization to the domain (e.g., 1 means the largest size and the lowest price). In spatial databases, ranking is often associated to nearest neighbor (NN) retrieval.Given a query location, we are interested in retrieving the set of nearest objects to it that qualify a condition (e.g., restaurants). Assuming that the set of interesting objects is indexed by an R-tree , we can apply distance bounds and traverse the index in a branch-and-bound fashion to obtain the answer.
We propose spatial ranking, which orders the objects according to their distance from a reference point, and non-spatial ranking, which orders the objects by an aggregate function on their non-spatial values. Our top- k spatial preference query integrates these two types of ranking in an intuitive way. As indicated by our examples, this new query has a wide range of applications in service recommendation and decision support systems. To our knowledge, there is no existing efficient solution for processing the top-k spatial preference query. A brute-force approach for evaluating it is to compute the scores of all objects in D and select the top-k ones. This method, however, is expected to be very expensive for large input data sets.