The Observer as Decoding Rule: Semantic Origin and Multi-Observer Invisibility in Zero-Entropy Ontology

Building upon the first three works of the projective ontology framework, this paper further clarifies the ontological status of the observer: the observer is not an information storage device, but a pure, living decoding rule. Information clusters are static, meaningless syntactic bitstreams; the observer as a rule maps syntactic bits into meaningful semantic experiences. We formalize two modes of rule-information interaction: when information can be defined by the existing rule, the rule remains unchanged; when information is undefinable, the rule undergoes uncaused random expansion, which is precisely the source of the observer's "aliveness" and free will. Since rules can only take information as input and cannot read other rules, no observer can observe another observer—the phenomenon of multiple observers is a projection of narrative coordination within the information cluster. We also derive the conservation relation between rule complexity and apparent physical entropy, extending the information entropy conservation equation to the rule-evolution framework. As an application, we provide a rule-decoding explanation for quantum interference and collapse. This framework further consolidates zero-entropy ontology and offers a formal foundation for the semantic nature of consciousness and the limits of solipsism.