Actra(ID:1785/act021)

Multiprocessing Smalltalk 

An exemplar-based, mutitasking, multiprocessing Smalltalk.
Lalonde et al Carleton University, 1985

used in DFACTT: Data Fusion and Correlation Techniques Testbed

A full function tactical SIGINT production system



Related languages
Actors => Actra   Influence
Smalltalk-80 => Actra   Influence
References:
  • Thomas, D.A., and Lalonde, W.R., Actra: The Design of an Industrial Fifth Generation Smalltalk System, Proc. of IEEE COMPINT '85, Montreal, Canada, Sept. 1985, pp. 13g-140. view details
  • LaLonde, W. R., D. A. Thomas, et al. (1986). "An exemplar based Smalltalk." view details Abstract: Two varieties of object-oriented systems exist: one based on classes as in Smalltalk and another based on exemplars (or prototypical objects) as in Act/1. By converting Smalltalk from a class based orientation to an exemplar base, independent instance hierarchies and class hierarchies can be provided. Decoupling the two hierarchies in this way enables the user's (logical) view of a data type to be separated from the implementer's (physical) view. It permits the instances of a class to have a representation totally different from the instances of a superclass. Additionally, it permits the notion of multiple representations to be provided without the need to introduce specialized classes for each representation. In the context of multiple inheritance, it leads to a novel view of inheritance (or-inheritance) that differentiates it from the more traditional multiple inheritance notions (and-inheritance). In general, we show that exemplar based systems are more powerful than class based systems. We also describe how an existing class based Smalltalk can be transformed into an exemplar-based Smalltalk and discuss possible approaches for the implementation of both and-inheritance and or-inheritance. DOI
          in SIGPLAN Notices 21(11) November 1986 (OOPSLA - Conference on Object Oriented Programming Systems Languages and Applications 1986) view details
  • Thomas, David; LaLonde, Wilf R.; and Pugh, John R. "Actra - a mutitasking multiprocessing smalltalk" Technical Report SCS-TR-92, Carleton University, May 1986. view details Abstract: DFACTT provides a full function tactical SIGINT production system through automation of every aspect of the Electronic Warfare (EW) process. By fusing and correlating raw EW sensor information about emitters on the battlefield, DFACTT produces detailed situation analysis using expert systems and object-oriented technology. This is achieved by providing automated workstations and seamless communications to every detachment of the Canadian Army's EW squadron.

          in SIGPLAN Notices 21(11) November 1986 (OOPSLA - Conference on Object Oriented Programming Systems Languages and Applications 1986) view details
  • Epstein, D. and W. R. LaLonde "A SMALLTALK window system based on constraints." view details
          in SIGPLAN Notices 23(11) November 1988 (OOPSLA '88) view details
  • LaLonde, W. R. and M. v. Gulik "Building a backtracking facility in SMALLTALK without kernel support." view details
          in SIGPLAN Notices 23(11) November 1988 (OOPSLA '88) view details
  • Thomas, D. A. et al. "Actra - a multitasking/multiprocessing Smalltalk." view details Abstract:
         The Actra project is investigating future generation industrial computer systems based on the actor or object-oriented metaphor. It is designed to provide an integrated, multi-user, multi-processor object-oriented program development environment for use in medium and high performance industrial applications dealing with complex man-machine systems. Typical areas include command and control systems, manufacturing systems, simulation and intelligent assistants. In this paper we have presented concurrent programming features of Actra a multiprocessor Smalltalk. The design builds on existing message passing primitives and requires minimal changes to the Smalltalk virtual machine and applications programs. We have introduced operations for creating and communicating between active objects(actors) which are consistent with the object-oriented viewpoint. The resulting system provides a powerful facility for performing anthropomorphic programming in a multitasking\slash multiprocessor environment. Extract: Introduction
    Introduction
    The Actra project is investigating future generation industrial computer systems based on the actor or object-oriented metaphor. It is designed to provide an integrated, multi-user, multi-processor object-oriented program development environment for use in medium and high performance industrial applications dealing with complex man-machine systems. Typical areas include command and control systems, manufacturing systems, simulation and intelligent assistants.
    Actra has been strongly influenced by the evolving theory of actors and incorporates the extensive software engineering contribution of Smalltalk-80. We define a new class of active objects called Actors, which encapsulate the behaviour of tasks. Actors are first class objects which can be created and sent messages just like all other Smalltalk objects. Actors are realized using the Harmony real-time kernel. The resulting system allows the natural evolution of object-oriented programming from uniprocessor to multiprocessor environments.
    The software and hardware for such systems can be viewed as a collection of communicating objects (both real and abstract) which together model the application environment. Most industrial applications do not require a massively parallel architecture such as those being proposed [HewittS0, Athas88]. We believe such requirements can be met using a conventional shared memory multiprocessor. The system uses readily available components (MC 68020 and VME bus). Using this approach, a cost effective solution that does not require a breakthrough in either semiconductor or interconnect technology has been developed. DOI Extract: Conclusions
    Conclusions
    We have presented concurrent programming features of Actra ,a multiprocessor Smalltalk. The design builds on existing message passing primitives and requires minimal changes to the Smalltalk virtual machine and applications programs. We have introduced operations for creating and communicating between active objects (actors) which are consistent with the object-oriented viewpoint. The resulting system provides a powerful facility for performing anthropomorphic programming in a multitasking/multiprocessor environment.

          in SIGPLAN Notices 24(04) April 1989 incoroporating Proceedings of the 1988 ACM SIGPLAN workshop on Object-based concurrent programming, San Diego view details
  • Philippsen, Michael "A survey of concurrent object-oriented languages" pp917-980 view details
          in Concurrency: Practice and Experience 2000 v12 view details