Application Data Structures Research Articles

A user interface toolkit based on graphical objects and constraints

One of the most difficult aspects of creating graphical, direct manipulation user interfaces is managing the relationships between the graphical objects on the screen and the application data structures that they represent. Coral (Constraint-based Object-oriented Relations And Language) is a new user interface toolkit under development that uses efficiently-implemented constraints to support these relationships. Using Coral, user interface designers can construct interaction techniques such as menus and scroll bars. More importantly, Coral makes it easy to construct direct-manipulation user interfaces specialized to particular applications. Unlike previous constraint-based toolkits, Coral supports defining constraints in the abstract, and then applying them to different object instances. In addition, it provides iteration constructs where lists of items (such as those used in menus) can be constrained as a group. Coral has two interfaces: a declarative interface that provides a convenient way to specify the desired constraints, and a procedural interface that will allow a graphical user interface management system (UIMS) to automatically create Coral calls.

A Picture-Building System

The picture-building system (PBS) deals with the problem of creating and manipulating data structures for applications using computer graphics. PBS has a data definition facility that enables one to specify structures needed for a given application, a manipulation facility for loading and editing the data, and displaying the image stored in the structures. The structures are defined in a relational data base and allow graphical attributes to be specified in the same way as nongraphical attributes. There is a deliberate attempt to separate data from programs which is in accord with other data-base developments. It is also possible to mix text and vector data with raster scan data which we have found to be very useful in some graphical applications. Some examples and a brief description of our color display system will be given.