Traditionally, the physical space and the virtual space are disjoint and distinct. Users in each space operate within the scope of the space, i.e, they may communicate among themselves but do not cross the boundary to the other space. However, technological advances in ubiquitous computing, smart interfaces and new augmented realities have made it possible for these two spaces to co-exist within a single space, the co (existing) space.
In a co-space environment (or cyber-physical system), the physical space and the virtual space interact simultaneously in real-time. Locations and events in the physical world are captured through the use of large number of sensors and mobile devices, and may be materialized within a virtual world. Correspondingly, certain actions or events within the virtual domain can affect the physical world (e.g. shopping or product promotion and experiential computer gaming). Thus, on one hand, the physical space is virtually enhanced with information. On the other hand, the virtual space is continuously refreshed with real-time, real-world information. Figure 1 shows the information flow within a co-space environment - data may flow within a single space, but more importantly, data also flows into the other space. It is this that distinguishes co-space from mixed reality (or augmented reality or augmented virtuality) - while mixed reality integrates the real and virtual worlds (e.g., augmenting live video imagery with computer generated graphics), it is done in a rigid and static manner, and does not capture real-time changes and their effects on either of the spaces.
In co-space, we can design innovative applications that provide experiences and opportunities that neither the physical nor the virtual spaces alone can offer. Some example applications include partnership in shopping among online and physical shoppers, an enhanced digital model that captures physical troop movement, location based games and social networking.
Within such a context, it is easy to see that large amount of data and information must flow to/from co-space in order to ensure that the real and virtual worlds are synchronized. This brings new challenges such as a need to process heterogeneous data streams in order to materialize real world events in the virtual world and more intelligent processing to send interesting events in the co-space to someone in the physical world.
To allow users to process and manipulate information seamlessly between the real and digital spaces, novel technologies must be developed. These include smart interfaces, new augmented realities, efficient storage and data management and dissemination techniques. In this paper, we first present a sample of promising co-space applications. Given that these applications are data-driven, and the potential size of the data that could be generated is enormous, we believe that the database community has much to offer to drive the growth of this field. Finally, we identify and present several challenges that we, as a community, can contribute to manage the large amount of data, the huge number of events and the massive number of concurrent users within co-space. These include the development of efficient storage and indexing methods, processing engines, parallel and distributed architectures.