This overview of structured modeling ideas is a suitable starting point. Read the whole thing without much attention to details. Since writing this article, I have (a) discovered that a level-by-level explanation of computationally active definitional dependency diagrams is the best way to explain SM's "universal" modeling paradigm, (b) formalized the SML language, (c) completed the FW/SM research prototype, and (d) done much related research.
This paper formalizes the SM modeling paradigm. Read Section 1, and then skim Sections 2 and 3 together with the figures in the appendix.
This pair of papers provides an example-based description of a notational system for SM, together with pointed discussion of SML's allegedly "notable characteristics". Read both papers straight through without much attention to language details. Keep in mind that SML is just one of many possible notational systems for the SM modeling paradigm; for example, I would like to see a hybrid notational system that is more explicitly graphical and hence closer to the underlying modeling paradigm.To learn more about SML, the next step would be my Working Paper 378, which is a long tutorial on the subject. Copies are still available.
This paper describes the functionality of an SML implementation built on top of Framework, and discusses the significance of certain features of general interest. There is also a more technical companion paper by Neustadter et al. giving details about design and implementation.
This can be read independently of the above papers. Although it is not on Structured Modeling per se, it details much of my philosophy about the sort of modeling environment that will some day transform model-based work. Some of the references to then-current work are now a bit dated, but I still believe as strongly as ever in the views expressed in this paper.