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

Chapter 4. Applying an Immune System Analogy to Data-Clustering Problems 104data-clustering system and an artificial immune system. A further system, the SparseDistributed Memory, SDM, which has already been shown to be analogous to the AISis then introduced in more depth. It is then shown how aspects of the SDM and AIScan be combined in order to derive a model theoretically capable of performing dataclustering.Finally, the remainder of the chapter lays the foundations for generatingan artificial data testbed which is used for testing two novel immune-based models,described in chapters 5 and 6.4.1.1 Data-Clustering with an Artificial Immune SystemConsider a database to represent an antigen universe: a single item of data in thedatabase represents an antigen that must be recognised by the host system. An antibodyproduced by the artificial immune system recognises a set of antigens in the antigenuniverse — in a data clustering context, those items recognised by a single antibody canbe considered to form a cluster, and the antibody itself represents a concise descriptionof that cluster. In biological terms, the affinity or size of the ball of stimulation ofthe antibody would determine the size of the cluster. Assuming all antigens in theuniverse can be recognised by the antibody set, then the number of antibodies presentdetermines the generality/specificity of the clusters; a small number of antibodies willresult in few clusters, and therefore each cluster represents a very general descriptionof the data. As the number of antibodies is increased, the specificity of the clusterand hence the concept it represents also increases. New data arriving in the data-baseis continuously presented to the system, which triggers the antibody set to adapt tothe new dataset, either by adapting existing antibodies, or creating new ones. This isexactly analogous to the primary response in the biological immune system.4.1.2 Data-clustering with a Sparse Distributed MemoryAs previously stated in chapter 2, [Smith et al., 1996] showed that immunologicalmemory belongs to the same class of associative memories as Kanerva’s Sparse DistributedMemory (SDM). In this work, they argued that the B-Cells and T-Cells ofthe immune system perform the same function as the hard locations in an SDM, and