Mads Torgersen

The Expression Problem Revisited

The expression problem (aka the extensibility problem) refers to a fundamental dilemma of programming: To which degree can your application be structured in such a way that both the data model and the set of virtual operations over it can be extended without the need to modify existing code, without the need for code repetition and without runtime type errors.

Design, implementation, and evaluation of the Resilient Smalltalk embedded platform

Most microprocessors today are used in embedded systems and the percentage of microprocessors used for embedded systems is increasing. At the same time development of embedded systems is very resource-consuming among others due to the lack of support for incremental development and for support for dynamic servicing and upgrading of deployed systems. This paper introduces the design and implementation of the Resilient System for embedded systems development which has as a design goal to support exactly this. Programs are written in a dialect of Smalltalk and executed on a compact, efficient virtual machine running on embedded systems. Programmers may connect to running virtual machines and service, monitor, or change the running systems. Furthermore, we present an evaluation of the Resilient platform in relation to the design goals through a case study of two development projects which successfully used the platform.