Franklin Gracer

Saving legacy with objects

Developers of application software must often work with “legacy systems.” These are systems that have evolved over many years and are considered irreplaceable, either because it is thought that duplicating their function would be too expensive, or because they are trusted by users. Because of their age, such systems are likely to have been implemented in a conventional language with limited use of data abstraction or encapsulation. The lack of abstraction complicates adding new applications to such systems and the lack of encapsulation impedes modifying the system because applications depend on system internals. We describe our experience providing and using an object-oriented interface to a legacy system.

TGMS: an object-oriented system for programming geometry

TGMS (tiered geometric modelling system) is an experimental system intended to reduce the difficulty and cost of developing new solid modelling applications while preserving investment in an existing, time‐tested, solid modeller. The application developer writes programs in the TGMS language, which consists of a base language augmented by data types (classes) for geometry. The base programming language is AML/X, an object‐oriented language intended for use in design and manufacturing applications. Solid modelling is done using an interface to GDP (geometric design processor), an existing, production‐quality solid modelling system. TGMS shows how a system written in a non‐object‐oriented language can be used as a base for an object‐oriented application programming environment.

Interactive Graphics for Volume Modeling

This paper describes the GRaphic INput subsystem (GRIN) of an experimental volume modeling system called the Geometric Design Processor (GDP) developed at the IBM Thomas J. Watson Research Center. Sitting at an interactive graphic workstation, a mechanical designer generates computer volume models of complex physical objects and mechanisms built up from primitive volumes, e.g., cuboids, cylinders, swept surfaces, etc., entered at any orientation in 3-dimensional space. Objects are represented in the model as polyhedral approximations. The central issue is the provision of an efficient, natural means for a mechanical designer to enter and interact with these models.

Interactive graphics for volume modeling

This paper describes the GRaphic INput subsystem (GRIN) of an experimental volume modeling system called the Geometric Design Processor (GDP) developed at the IBM Thomas J. Watson Research Center. Sitting at an interactive graphic workstation, a mechanical designer generates computer volume models of complex physical objects and mechanisms built up from primitive volumes, e.g., cuboids, cylinders, swept surfaces, etc., entered at any orientation in 3-dimensional space. Objects are represented in the model as polyhedral approximations. The central issue is the provision of an efficient, natural means for a mechanical designer to enter and interact with these models.