The goal is to develop a definition for 'system' that could used by the full range of “system” disciplines: Systems Science, Applied Systems Science and Systems Engineering across the major system types: natural, social and engineered.

Essentially a return to first principles which might open the playing field to a broader audience yielding a better answer.

I expect that a major (and likely correct) push back on this initial proposed definition is that it is too simple. Even if true, it can be used to agree that we are discussing a 'system', even across representative from the different system disciplines, and from there determine what is unique about THIS system, so we have a sub-class. As we work through these specializations, we will be forming the Taxonomy for systems which can form the base for a set of Ontologies and associated Schemas but with broader involvement.

A system is a bounded interval of spacetime for which the the inputs and modified outputs, consisting of matter and/or energy and/or information, can be observed and specified.

If we accept this definition, then:

1. Since a system exchanges inputs and outputs with “something”, “something” can be labeled as another system
2. Systems can either exist alongside a system in some environment or within other systems

1. Does this proposition provide a way to determine if “what we are observing” is a system?
2. Does this proposition capture everything we currently think is a system, up to the “Universe” (discussion about what is beyond 'space-time' to exchange with or 'wrapping around' and exchanging with itself is philosophy not science at this time) and down to “fundamental particles” (things not composed of smaller things)?
3. Do the proposition and theorems “feel” like they “makes sense”?