Gajski-Kuhn chart

The Gajski-Kuhn chart (or "Y diagram") depicts the different perspectives in VLSI hardware design. Mostly, it is used for the development of integrated circuits. Daniel Gajski and Robert Kuhn developed it in 1983. In 1985, Robert Walker and Donald Thomas refined it.
According to this model, the development of hardware is perceived within three domains that are depicted as three axis and produce a Y. Along these axis, the abstraction levels that describe the degree of abstraction. The outer shells are generalisations, the inner ones refinements of the same subject.
The issue in hardware development is most often a top-down design problem. This is perceived by the three domains of behaviour, structure, and the layout that goes top-down to more detailed abstraction levels. The designer can select one of the perspectives and then switch from one view to another. Generally, the design process is not following a specific sequence in this diagram.