Visual Query Interfaces

A Visual Query System (VQS) can be defined as a system that uses a visual representation for both the domain of interest and requests related to the domain. In particular, as the purpose of any VQS is to provide access to the information contained in a database, the main users' tasks are understanding the database content, focusing on meaningful items, finding query patterns, and reasoning on the query result. The first graphical query language which was referred to as Query-By-Example was introduced in the mid-1970s, and a wide range of implementations were built using these concepts and there are several tools using this paradigm today. In this chapter, we will first review the main approaches to visual queries, and later on we consider recent advancements, finally focusing in the field of data stream processing.