Persistent Graphical Objects in Procol

Persistent objects are objects whose contents may outlive the execution time of the program. This paper describes the process of introducing persistent objects in the object-oriented programming language Procol. The strength of persistent objects in an object-oriented programming language is the integration of a database system with programming language. Persistent objects make the program development easier, because the programmer does not have to implement the explicit loading and saving of data. Besides the general functional aspects, special attention is paid to graphical applications in order to deal with their specific geometric requirements. For example, it must be possible to find, in an efficient manner, all graphical objects that fall within a given region. These issues, persistent objects and their geometric rquirements, have not yet got the attention they deserve in the literature covering object-oriented graphical systems where modeling and functional aspects dominate