Imagine a computer model of the universe. The past, the present, the future, every event that has or will ever occur. This is The Universal Model.
Clearly there would be some major limitations on the quality this model. You can't have a perfect model of the present stored in the present (not to mention storing the past 13.7 billion years or the next googols of years predicted by our current best cosmological theories). What I have in mind is a kind of massive service where you can ask for information about the universe and retrieve those answers if they are available. The Universal Model is an abstract model that is, at best, partly built, as needed, in order to fulfill a query about it.
Let me try to flesh the idea out a little more. Imagine any system that needs to "answer a question" of some sort. Maybe you're typing a question into a search box. Maybe you're "asking" Google Earth to display a useful image of downtown Seattle. Maybe you're checking the weather for next weekend. Now, imagine a system that can fulfill the query in terms of questions about the way the universe is, plus some processing. In other words, imagine converting or compiling down the question into explicit questions about the universe. For Google Earth this could amount to rendering the image of what would be seen from a specific point and orientation above Seattle, right now. For the weather, you need to look at the 4D volume of space above the location you're at and from Saturday morning until Sunday evening. You'd then need to process the physical description to extract the amount of cloud and rain that's present, and then convert that into a label saying "sunny" or "partly cloudy" based on the context.
Now, again, since we can't store the whole universe, we need methods to fulfill the queries about The Universal Model. This could be done in a number of ways. If only a small subsection of the model is required, which would be the case in the vast majority of queries, then you could invoke specialized services designed to answer queries of that type. Queries about the nature of the weather on the weekend could be fulfilled by invoking weather models, for example.
Consider an analogy. When one wants to automatically translate a document from one language to another, one method would be to build a language-agnostic conceptual representation of the meaning expressed by the sentence and then to express that conceptualization in the other language. This solution would be extremely powerful because it preserves all relevant information and is scalable. (For any new language, you only need to be able to map it to The Language Model and then express that, in any language you want.) The downside of this approach is that we haven't been able to achieve any kind of mapping like this, partly because we don't know exactly what The Language Model would look like and because language is very context-dependent. Instead we build lower level representations, but not as "low" as The Language Model and then take a shortcut on that level of representation.
This is what would need to be done with The Universal Model as well. We take shortcuts while "translating" our query into an answer. This is a general problem for any sort of "conversion".
If, like me, you believe that all propositions are made true or false by the universe, then in the case of The Universal Model, the top layer would be any coherent question. So even our idealistic Language Model could be seen as a special case "hack", albeit at one of the lower levels of this hypothetical universal question answering device, that has The Universal Model at the bottom. The Universal Model is the most ideal model possible.
That's the idea anyways; I'm not sure it fully holds up; Take it with a grain of salt; etc; etc.
I wanted to get the idea out there rather than dwell on it too much and then end up not posting anything. Please comment and refine and clarify the idea further for me if you find it interesting!