in a recent column (http://blog.stephenwolfram.com/2015/12/what-is-spacetime-really/) Stephen discusses his idea of a network model of the universe (originally presented in chpt. 9 of NKS and in his earlier blog (http://blog.wolfram.com/2007/09/11/my-hobby-hunting-for-our-universe/). It is worth noting that Albert Einstein had also thought in tihs direction. here are some comments of Einstein that i have located:
"But you have correctly grasped the drawback that the continuum brings. If the molecular view of matter is the correct (appropriate) one, i.e., if a part of the universe is to be represented by a finite number of moving points, then the continuum of the present theory contains too great a manifold of possibilities. I also believe that this too great is responsible for the fact that our present means of description miscarry with the quantum theory. The problem seems to me how one can formulate statements about a discontinuum without calling upon a continuum (space-time) as an aid; the latter should be banned from the theory as a supplementary construction not justified by the essense of the problem, which corresponds to nothing "real". But we still lack the mathematical structure unfortunately. How much I have already plagued myself in this way!" - letter to Walter Dallenbach, Nov 1916
"In any case, it seems to me that the alternative continuum-discontinuum is a genuine alternative; i.e. there is no compromise here. In [a discontinuum] theory there cannot be space and time, only numbers [...]. It will be especially difficult to elicit something like a spatio-temporal quasi-order from such a schema. I can not picture to myself how the axiomatic framework of such a physics could look [...]. But I hold it as altogether possible that developments will lead there [...]."
"I consider it entirely possible that physics cannot be based upon ... continuous structures. Then nothing will remain of my whole castle in the air including the theory of gravitation, but also nothing of the rest of contemporary physics"
"The problem seems to me how one can formulate statements about a discontinuum without resorting to a continuum (space-time) ... But for this we unfortunately are still lacking the mathematical form. How much I have toiled in this direction already!"
Its worth ponting out that the first comment was made in 1916 at the same time that Einstein created his theory of GR and not later, when he was in what many physicists consider (incorrectly, and often condescendingly) to be in his intellectual dotage.
note: if you are interested in other discrete models of the universe, you might look at the publications of Raphael Sorkin (http://www.perimeterinstitute.ca/personal/rsorkin/some.papers/) related to the causal set approach.
finally, let me just point out that whether one prefers a continuum or discontinuum approach, these are MODELS of realty, not representations of reality. in the words of John von Neumann:
"The sciences [...] make models [that are] mathematical constructs which, with the addition of certain verbal interpretations, describes observed phenomena."
note that In this statement, von Neumann accepts the Popperian falsifiability criterion for science, rather than the post-empirical confirmation criterion nonsense recently proposed by Dawid and finding some support amongst theoretical cosmologists who have been unable to develop experimentally testable models such as string theory and GQL theory.