Design and implementation of a relational query language with teams

We introduce the concept "team" and incorporate the team query into the data language SQL. Existing relational query languages use tuple variables of tables to specify required data. Queries that are expressed by these languages are used to get all the data which satisfy the specified conditions. While a team variable represents a subset of a table, a team query is used to retrieve all the teams that meet certain constraints. We introduce team qualifications and briefly describe team query processing. The search space of a team query may be very large. Therefore, instead of using conventional breadth-first search method, we adopt a depth-first search method for query processing. Thus, users can always get a result if one exists.<>