Immunology as a Metaphor for Computational ... - Napier University

Chapter 7. Conclusion 188most importantly, the memory is self-organising. In addition, the immune system possessesthe ability to ’forget’ cases which are no longer useful, therefore improving theefficiency of the system.[Hunt et al., 1995] compared an immune-network to several other forms of casememory,namely linear memories, hierarchical memories, nested memories, decisiontrees,and knowledge-guided indexing. The analysis showed when compared to thesememories, only the immune system has a structured memory, is inherently incrementallyadaptable, can automatically create its memory structure without a memory ’designer’identifying the appropriate structure, is inherently self-organising and providesan implicit mechanism for case-forgetting. Furthermore, when considering retrievalmechanisms, the immune system can focus search towards similar cases and can handlenoisy or missing data. None of the previously mentioned forms of memory exhibitboth these properties. However, the immune system has one potential drawback in thatit is not deterministic, and does not necessarily return the same result given the sameinputs. This is in contrast to the other forms of memory considered.Is then, a CBR system a suitable methodology for tackling scheduling problems? Certainly, in the problem described in chapter 3, a database of previous cases, i.e.schedules, could be built up. Straightforward matching algorithms could be utilised tomatch partial schedules and environmental conditions to cases in the databases, as ingeneral we would only be dealing with integer representations. Thus, it is conceivablethat a CBR approach might be adopted in some circumstances. However, a CBR approachhas a major drawback in that it is not possible to produce entirely new schedulesfrom such a system, that do not resemble existing cases in the database. This is not trueof an immune system approach in which the building blocks from which schedules arebuilt can be recombined in many ways to produce novel schedules which are appropriatefor the current conditions. Thus, this fact might prove a significant advantage foran immune-system rather than CBR approach in this case.7.3.2 Other Approaches to Data-ClusteringIn [Timmis et al., 1999], the author compares the performance of an immune-networkalgorithm for clustering with a simple clustering technique known as Single Linkage