AIAI CBR Shell

The AIAI CBR Shell is a generic tool for case-based reasoning. The tool performs classification based on case comparison. The parameters of the algorithm can be varied: the number of nearest neighbours considered can be specified, the weights can be set manually, or the weights can be optimised by a genetic algorithm. The accuracy of the algorithm is measured by a leave-one-out evaluation.

A case is simply a comma delimited list of values (numbers or strings), one of which denotes the class to which the case belongs. E.g. the Iris data has 5 fields, the final being the class:
5.1,3.5,1.4,0.2,Iris-setosa
4.9,3.0,1.4,0.2,Iris-setosa

The CBR Shell is made available without warranty or guarantee for academic purposes only.

Download and Installation

If you wish run the CBR as an application, then download the jar file: click here. To run under Linux or Mac OS X, type java -jar cbrapplet.jar under XP open with javaw or from a shell.

You may wish to copy the files from the table below (shift-click to download, or use the `Save Page As' option in Netscape 6 and use the files names given.

Using the shell:
Load a casebase file (the key is automatically loaded,but must be in the same directory).
Step presents the results of each case analysis - the screen should appear as shown below after the casebase is loaded and Step is executed:

Run goes through the casebase and calculates the accuracy.

CBRSettings: set K or threshold, select weight structure:

Genetic Algorithm: the GA optimises the weight structure. Each chromosome represents the weights 1..N, as applicable to a casebase of cases each having N fields. The GA does not alter the value of k.

Initially, set the no. of chromosomes to a small value e.g. 20.
Run setsup and starts the GA. The results of each generation are printed to the command line.
The mapping from bits to weights can be configured. The default number of bits is 2, giving a total of 2**bits = 2**2 = 4 weight values. The weight values must be listed in the Mapping text field. The bit values 00-11 correspond to 4 weights:
00->weight-1, 01->weight-2, 10->weight-3, 11->weight-4
In the example above, 00->0.0, 01->1.0, 10->2.0,11->4.0
meaning that 00 in the chromosome is decoded as a weight of 0.0, 01 is decoded as 1.0 and so on. The CBR is run once, using these parameters, to evaluate each chromosome. The usual crossover and mutation operators are applied. NOTE: there may be problems with this option under windows.

Casebase and Key Files

The Casebase Data: the data must be in comma delimited form, newline delimits a case. The first line of the casebase must contain the name of the key file, the second states the goalfield (i.e. the class to which the data/record/case belongs). See the example files.

The Key: this file defines the type of matching that is done on each field in each case. The matching types include:
num - numerical comparison by evaluating the ratio of 2 numbers
stringexact - string comarison (equality test)
trigram - comparison of strings/sentences/paragraphs by trigram matching

The Iris key is simply:
num weight: 1.0
num weight: 1.0
num weight: 1.0
num weight: 1.0
stringexact weight: 1.0
meaning there are 4 numerical fields, and a string field. All weights are 1.0. In fact, the final field is the goal field and is always treated as a string (the weight is ignored).

Contact: Stuart Aitken
Email: s.aitken@ed.ac.uk