Dissimilar software

Cranfield Algorithm for Fault-Tolerance (CRAFT) Food Taster Distinct and Dissimilar Software Recovery Blocks... 

In multiple-version dissimilar software, a set of two or more computer programs are developed separately (and independently) to satisfy the same functional requirements. Errors specific to one of the versions should be detected by comparison of the outputs between the different versions. When multiple-version dissimilar software is used in redundant computer systems, the likelihood of the same errors in both systems is theoretically significantly reduced, thereby achieving a higher level of safety for the system. Multiple-version dissimilar software involves applying the dissimilar design concept to software. 

N-version programming is a system design technique that involves producing two or more software components that provide the same function, but in different ways. This approach is intended to avoid sources of common errors between redundant components. N-version programming is also referred to as multi-version software, dissimilar software, or software diversity. 

See Design Diversity and Dissimilar Software for additional related information. 

Similarity is often used as a general term to encompass either similarity or dissimilarity or both (see Section 6.4.3, on similarity measures, below). The terms "proximity" and distance are used in statistical software packages, but have not gained wide acceptance in the chemical literature. Similarity and dissimilarity can in principle lead to different rankings. 

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The first application of a computational method to select structurally diverse compounds for purchase started in 1992 at the Upjohn Company, which predated the formation of Pharmacia Upjohn by about three years. The basic approach selected compounds using a method based upon maximum dissimilarity and was implemented using SAS software [11]. This later evolved into the program Dfragall, which was written in C and is described in Section 13.6.3. Basically, a set of compounds that is maximally dissimilar from the corporate compound collection is chosen from the set of available vendor compounds. Early versions of the process relied solely on diversity-based metrics but it was found that many nondrug like compounds were identified. As a result, structural exclusion criteria were developed to eliminate compounds that were considered unsuitable for... 

Gillet, V. J. and Willett, P. (2001) Dissimilarity-based compound selection for library design. In Combinatorial library design and evaluation. Principles, software tools and applications in drug discovery, Ghose, A. K. and Viswanadhan, A. N. (eds.), Marcel Dekker, New York, pp. 379-398. 

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