What do you mean with "situation"? do you use situation as a an equivalent for context? (meaning, physical, cultural, etc.)? if so, yours is a great question! (also situation as context is barely mentioned in the most classical definition of Social Psychology as a science)

In Yang, Read, & Miller's article, based on a review of the literature on situations, we suggested that "The concept of situations" (2009) has generally been viewed as "a combination of the individually interpreted, implicit, and unique understandings, and the culturally shared, explicit, and common understandings of the surroundings that produce and constrain human behavior." (p. 1020).

Certainly contextual features are critical to situational meaning and our responses to them. Steve Read and I (1998) argued that situational concepts (e.g., a challenging situation, a threatening situation, a frustrating situation; a helpful situation; a vindictive situation; etc.) economically instantiate the gist of culturally recurring episodes or stories. That is, a "vindictive situation" might be one where the following situational script (as culturally defined) might have slots satisfied as follows (In the past, this person x did something to y, with bad effect, and x intended it so; Now, y can do something (or does do something) to x, with bad effect, and y intends (intended) it so) On the other hand, the concept "vindictive" is not even a word in many cultures.

But, across cultures, situations might be thought of as sequences of one or more stories where for each story there are a series of slots such as "who" does what "to whom" "under what circumstances(and with what resources)" with "what effect" and "why" -- Of course the same situation can be understood from potentially a number of perspectives (even by the same perceiver). By different perceivers a similar story structure (and series of stories) could result in the perception of different "situations" -- for example, X did this thing to Y, and it was bad, might be viewed by Y and Y's supporters as a victimization of Y situation and by X supporters as a victory situation.

Sometimes opposing groups in a conflict might use the same term (e.g., fiasco) to describe a conflictual impasse (or stalemate) situation. Consider the current political situation in the US. People with leanings towards the left and the right could all agree it is a situation that might be best labelled "a fiasco." But, the meaning of that situation is quite different on the left and on the right because those from different groups (subcultures perhaps) fill slots in the scenarios differently in terms of who is doing what to whom, why, with what effect (and therefore who is responsible for the stalemate), they have access to different resources (and media) and have different goals and motives regarding things like the affordable care act that affect how they view the sequence of events and what they think needs to happen to have a successful resolution.

In Yang et al. (2006) we argue that "the essence of a situation is its affordance of human goals, and that situations are largely characterized by...goal processes (what happened, is happening, or might happen to people's goals) and goal contents (the specific goals afforded in the situation) -- all of course taking into account the different "lenses" and culturally shared /individual meanings/understandings of actors and observers.

Milgram pointed to the problem we still confront:

"Ultimately, social psychology would like to have a compelling theory of situations which will, first, present a language in terms of which situations can be defined; proceed to a typology of situations; and then point to the manner in which definable properties of situations are transformed into psychological forces in the individual."(Milgram, 1965, p. 74).

To computationally model the dynamics of situations I find myself lamenting that I really don't know what are the critical variables/parameters that differentiate one situation from the next in any systematic way as it unfolds "in situ" (or in context) moment by moment because that seems rarely studied or described.

My question is really, why is following up on Milgram's suggestion so difficult? Is the problem with the available tools to adequately address this? Is the problem that the answers to this might require a level of description that would not be well received in the field? (and if so, why) Is the problem that we have tended not to think about and study things as they unfold over time? That is, what holds us back from understanding situations more systematically?

Discursive Psychology considers psychological concerns as features of situated practices. Exactly what does this mean - 'situated practices'?

I would like to read this article before i can make useful contributions, but so far what i have read is interesting and would like to follow further.