information visualization  information visualization, an increasingly important subdiscipline within the field of human computer interaction (hci) [13], focuses on visual mechanisms designed to communicate clearly to the user the structure of information and improve on the cost of access to large data repositories. in printed form, information visualization has included the display of numerical data (e.g., bar charts, plot charts, pie charts), combinatorial relations (e.g., drawings of graphs), and geographic data (e.g., encoded maps) [1, 9, 16]. in addition to these "static" displays, computer- based systems, such as the information visualizer [2] and dynamic queries [15] have coupled powerful visualization techniques (e.g., constraints, 3d, animation) with near real-time interactivity, i.e., the ability of the system to respond quickly to the user's direct manipulation commands. another important aspect of computer- based information systems concerns the dual communication with user and machine, which motivates the concept of visual formalism that has been introduced by harel: "the intricate nature of a variety of computer-related systems and situations can, and in our opinion should, be represented via visual formalisms; visual because they are to be generated, comprehended, and communicated by humans; and formal, because they are to be manipulated, maintained, and analyzed by computers" [12].  while historically hci and database research were kept separate, the interests of both research communities have been converging, mainly in what concerns the topic of information visualization. in the database community, the focus on information visualization started with research in visual query languages, where the visualization of schema and/or database instances is common (for a survey, see [4]). recently, a new generation of database systems is emerging, which tightly combine querying capabilities with visualization techniques and are information visualization systems in their own right [3, 8, 11]. database applications that access large data repositories, such as data mining and data warehousing, and the enormous quantity of information sources on the www available to users with diverse capabilities also provide hci researchers with new opportunities for information visualization (see, for instance, the acm report on strategic directions in hci [13], the reports of the "fadiva" working group [10], and the work presented in [14]).  the objective of this special issue is two-fold: to compile some of the most recent research on information visualization from both communities, and to make it available to a large readership whose main interests lie in the management of data. the eight papers in this issue cover fundamental topics in information visualization, including tailorable multi- visualizations (i.e., the ability of the system to provide the user with alternative visualizations, depending on their suitability to different data, tasks, and users' preferences); near real-time interactivity when dealing with very large data sizes; effective display and color usage, and multidimensionality. a short overview of each paper follows.  tiziana catarci isabel f. cruz