Design principles

[epatters]

The purpose of this issue is to collect and discuss preliminary "design principles" for the DSO, as they come up. At some point we'll create a more permanent document.

[epatters]

Here's one to get started, following up on #2:

Don't create new types that simply intersect existing types, unless the intersection has a preexisting name in standard usage or is needed to specify the domain of a function. E.g., we don't need to define a feature-extraction-model type that is-a feature-extraction and is-a model.