Followup to: Reduced representation of alternatives.
Scene graph represents information about environment, focusing on certain objects and relations, at a certain level of description. Each element of representation leaves fair amount of uncertainty, specifying only a coarse picture. At the lowest level, labels encode classes of properties without discriminating among the properties within represented class. Finer distinctions are expressed through the graph structure in which labeled nodes are organized. Common arrangements of local structure can later be summarized in maps.
Similar states of information about environment are represented by similar scene graphs, which allows to infer ways of transforming representation without significantly distorting represented information about environment. Many details and high-level properties of environment implicitly described by the scene are absent in the representation but known based on scenes encountered in the past. Scene can be transformed to replace a given description of environment with one that is expressed in terms of more familiar structural contexts, and that doesn’t leave out properties that are usually represented explicitly.
Details included in representation, especially restored ones, are of different levels of uncertainty. Furthermore, since patterns are represented implicitly, uncertainty of the same detail can vary between its different local reconstructions by structure waves. Essentially, stochastic process of modification of map salience through propagation of structure waves balances uncertainty of different elements of representation, by enumerating sufficiently certain structural contexts. Salience of a map is influenced through different routes, since the same map can be a part of many different patterns, and the same pattern can be suggested as sufficiently likely by many different structure waves.
A pattern that is used in many contexts in the scene, is of high certainty by itself, while each of its instantiation points can have different levels of uncertainty, and all of the details in the scene are very unlikely to be correct simultaneously. Similarly, contradicting properties generate alternative scenes of higher uncertainty than the scene without contradicting properties, but common areas of these alternative scenes are still pretty certain.
Reduced representation can be thought of as a state of knowledge that allows to answer questions. Structural contexts or patterns are specific answers, and structure waves are questions. Answers to different questions can contradict each other when considered by themselves. Different parts of the scene can have contradictory properties, just as alternative properties of the same part of the scene contradict each other. Which color is a zebra? Different colors at different points. What color is an animal? Depends on which animal it is. Encoding different structures of alternative states of the scene allows to represent the structure of uncertainty about the scene with the same expressive power as used for describing the fixed structure of a single scene.
Contradictions can be resolved either in the question, by specifying additional details that allow to give a simple answer, or in the answer, by making it conditional, by enumerating alternatives. Different alternatives in the answer can be recast as elaborations to the previous question, and this is one way of exploring an overly complex answer to an overly general question, such as the structure of the whole scene. Structure waves are iteratively refined questions shaped by state of knowledge about the scene, and structural contexts they restore are both local answers and iterations of further refinement. Scope of the question can include elements of alternative structures of the scene, or elements of different parts of the same structure of the scene expressed in common pattern, erasing the difference between these cases.
