An algebraic structure is described
that forms the innermost core of the object model of the Ruby programming language.
The structure, denoted S1, is induced by superclass and eigenclass links between
Since Ruby is a serious candidate for the
most object-oriented programming language in the world,
the S1 structure can be considered to be the
core structure of object technology
We provide a simple set-theoretic representation showing how the
structure can be interpreted via
set inclusion and set membership.
We also describe lazy evaluation of infinite eigenclass chains.
Finally, the Smalltalk precursor of the S1 structure is discussed.