Martin (1992: 107):
These options [in the IDENTIFICATION network of Fig. 3.4] do not distinguish within partial pronominal reference between somebody/someone/something and anybody/anyone/anything. The contrast is between [restricted] reference to a particular member of a class and [unrestricted] reference to any of its manifestations.
 To be clear, the discourse semantic network in Fig. 3.4 includes choices defined in terms of grammatical form, pronominal vs nominal, instead of semantics. The inconsistency (confusion) is one of stratification (symbolic abstraction).
 This again confuses a potential referent with the items that refer to them. To be clear, these non-specific pronouns do not function as reference items, since they do not signal the recoverability of an identity.
 The claim here is that
- some(body/one/thing) is a restricted reference to a particular member of a class, whereas
- any(body/one/thing) is an unrestricted reference to any member of a class.
However this does not characterise the difference in deixis between the two sets, as demonstrated, for example, by we stopped for something to eat, in which something is not a restricted reference to a particular member of a class of food.
To be clear, Halliday & Matthiessen (2014: 368) classify the deixis of some and any as follows: