classification-jop.arff:

@relation 'classification-jop'
@attribute X1 real
@attribute X2 real
@attribute C1 {one, two}
@data
10.0,12.2,one
21.1,24.3,two

clustering-jop.arff:

@relation 'clustering-jop'
@attribute X1 real
@attribute X2 real
@data
10.0,12.2
11.0,9.5
21.1,24.3
20.1,22.3

regression-jop.arff;

@relation 'regression-jop'
@attribute X1 real
@attribute X2 real
@data
10.0,12.2
15.0,16.5
21.1,24.3
25.1,28.3