To define properly datasets, the notion of sample should be introduced first. A sample is defined as polymorphic tuple. The size of the tuple will be by definition the arity of the sample itself.
is a collection of samples, that
size, which in turn can be infinite,
Hence the dataset implements the notion of sequence.
The descriptive power of the datasets in Unit Test Framework comes from
Only "monomorphic" datasets are supported, which means that all samples in a dataset have the same type and same arity  .
As we will see in the next sections, datasets representing collections of different types may be combined together (e.g.. zip or grid). These operations result in new datasets, in which the samples are of an augmented type.