(CONTINUATION FROM ABOVE POST)
Let's analyze my personal "operational" philosophy when applied to the framework of the Pavia derivation of QT. The fundamental notion of the entire framework is that of "test", which is a collection of outcomes, and is represented by a box with wires--"the systems". The outcomes have the objectivity status: a deterministic outcome can be the simple fact that the box is a mirror, or a laser on the optical table. However, the wires--"the systems"--are only partially operational, they are mostly theoretical notions. For example, we put a laser in front of a detector, and the wire here represents the laser beam. It is true that the laser beam can be "seen" in a smoky air, and we can definitely "align" the two boxes by a suitable protocol. But, at the very end, when we represent the wire connecting the "preparation" (laser) with the "observation" (detector), we say that it represents the traveling "photon", and, as such, we cannot "see" it. Such a system is defined operationally only in part, and, indeed, it is mostly a theoretical notion. It is our way of causally connecting the two objective events "laser-on" and "detector-click". The same can be said of the "field mode". Both kinds of systems are the support of the "information", the register where information is written and read. Informationalism coincides with operationalism as long as information means classical data, "outcomes". "States" are preparation protocols (probabilistic equivalence class of them, to be precise), and, as such, they are operational notions. The same applies to "effects" and " transformations". But it is not the same for the "systems". Systems are theoretical notions, and, as such, their specific instance is theory-dependent, e.g. they can be classical bits, particles, field-modes. When we interpret them as causal connections between objective events, they become theoretical notions, since, at least, we need to restrict to causal theories. And, when interpreted as causal connections, they are "subjective", and this subjectivity reconciles my notion of causality with the Humean one.
Thus, in conclusion, "informationalism" is not equivalent to "operationalism" a la Bridgman.
*I am not against onthologies, but only against naïve ones*
As I wrote in my essay, I consider onthologies as powerful ways of thinking, tools for analyzing mechanisms visually and efficiently. But they are only tools, temporary tools subjected to the evolution of theory. They do not "actually exist" as such out there. They are not the real objects casting the "shadows" that we see.
Is it the Planck scale a new ontology? It will become a full ontology when we will clearly understand the whole physics at that scale. Consider for example the existence of mechanisms, as the "relative locality" of Amelino-Camelia and Smolin, where events delocalize depending on the reference frame. The more closely you look at "reality" the more it becomes "blurred". It is not a veiled reality. It is space-time that emerges in this way from quantum systems in interaction. There is no "empty space" filling the gaps between the denumerable entities. Space as we imagine in the current physics is an ontology that must be changed. Space is more as a blurred quantum-digital screen, which gets a huge resolution when you'll look at it from far apart.
*SR is operational. But, operationally, the relativity principle is not logically mandatory. On the top of this, GR is no longer operational*
As was shown by Ignatowski in 1910, Lorentz transformations can be derived from the simple requirements of linearity, symmetry between any two observers, and the Galileo's principle, the latter including homogeneity and isotropy of space and time. Einstein in his more mature derivation of SR used the Galileo principle, applying it also to electromagnetism. The impression that we got from this derivation is that such a fundamental principle is essentially indispensable to do science, that we cannot even state a physical law if it cannot express it in a way that is frame independent. This is not logically necessary. The physical law can be stated in a preferred frame if we know how to change it when changing the frame. Indeed this is what happens in practice, since we cannot avoid using the frame of fixed stars as a reference inertial frame. So, operationalism has not much to do with the relativity principle as such: SR is mostly based on the no-preferred-frame credo. What is truly operational are the Einstein's clock-synchronization protocol and the use of synchronized clocks to establish a full coordinate system by sending light back and forth between events. But such a protocol is strictly classical. In a Planck world you need quantum clocks, you need to send signals of quantum nature, which spread and have intrinsic imprecision.
Just a final comment on GR. The bending of space due to mass is a purely theoretical ingredient needed to mimic gravity: it is no longer just the equivalence principle. As such, GR has no longer an operational basis. Einstein admitted that, and stated that for a formal system to qualify as a physical theory it was "not necessary to demand that all of its assertions can be independently interpreted and 'tested' "operationally" [See "Operationalism on Stanford Encyclopedia of Philosophy"]. Then, allow me to say that the "bendable" space of Einstein is not more ontic than the emerging space of the Planck scale: it is just classical.
(CONTINUES)
