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June 28, 2005

Patent Law and Layers of Abstraction

In his talk yesterday (see my previous posting), Drew Endy talked about how some of his work is shifing towards designing biological systems at higher layers of abstraction. The idea of "layers" (or "levels") of abstraction is deeply engrained in the way engineers, and computer scientists in particular, think about systems. I've argued elsewhere that some of the problems with software patents could be fixed if patent law recognized the distinction between different layers of abstraction and focused its attention on the layer(s) where innovation is actually occurring in a particular field.

If you're not familiar with the concept of "layers of abstraction," imagine that you're designing a toaster. You might design the toaster as follows:

1. Start with the very high-level (i.e., very abstract) goal of designing a machine to toast bread.
2. Then you might identify the functions that the toaster needs to be able to perform, such as holding bread, heating bread, detecting when the bread has been toasted to the desired darkness, and ejecting the bread. Identifying these functions is called "functional design."
3. Then you might design the physical components for performing the functions described above, such as heating elements for heating the bread and springs for ejecting the bread. Designing these components is called "physical design" and is often what we think of as "inventing."

Once you've designed and built your toaster, there is of course only a single physical toaster. But you can still think about and describe the toaster in terms of its "physical layer" (its physical components) and its "functional layer" (the functions it performs). Machines and other systems are often designed and described in terms of many such layers in addition to the physical and functional.

It is possible to innovate in any of these layers. Mechanical engineers traditionally have innovated in the physical layer by designing new physical components or new combinations of existing physical components. Computer programmers traditionally have innovated in the functional layer by writing programs consisting of new functions or new combinations of existing functions.

But physical innovation holds a special place in patent law, as the result of assumptions that are no longer valid. One example of patent law's attachment to the physical layer is section 112, paragraph 6 of the U.S. patent statute, which says that patent claims written using functional language are to be limited in scope to the specific physical structure of the invention as described elsewhere in the patent. This section hard-wires the physical layer as the upper limit on the layer of abstraction at which an invention may be claimed.

This legal distinction between the physical and functional layers made sense when the focus of most innovation was the physical layer, and when there were no computers or other means available to automatically produce physical implementations of innovations described at higher levels of abstraction. But these assumptions are no longer valid, and patent law needs to become more flexible in response by focusing protection on the layer(s) of abstraction at which innovation is actually occurring in the real world. In future postings on this site I will explore ways in which patent law could be reformed to achieve this goal. I will also consider potential problems with such reforms.

Posted by Robert at June 28, 2005 9:31 AM
category: Philosophy of Computing | Software Patents

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