This record describes an abstract operation. It is a potential
step of a workflow that has not yet been bound to a concrete
implementation. It specifies an input and output signature, but
does not provide enough information to be executed. An
implementation (or other tooling) may provide a means of binding
an `Operation` to a concrete process (such as `Workflow`,
`CommandLineTool`, or `ExpressionTool`) with a compatible signature.
