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54 Chapter 2 Understanding and conceptualizing interaction

2.3.3 A case of mix and match?
As we have pointed out, which kind of conceptual model is optimal for a given ap-
plication obviously depends on the nature of the activity to be supported. Some are
clearly suited to supporting a given activity (e.g., using manipulation and naviga-
tion for a flight simulator) while for others, it is less clear what might be best (e.g.,
writing and planning activities may be suited to both manipulation and giving in-
structions). In such situations, it is often the case that some form of hybrid concep-
tual model that combines different interaction styles is appropriate. For example,
the tourist application in Activity 2.2 may end up being optimally designed based
on a combination of conversing and exploring models. The user could ask specific
questions by typing them in or alternatively browse through information. Shopping
on the Internet is also often supported by a range of interaction modes. Sometimes
the user may be browsing and navigating, other times communicating with an
agent, at yet other times parting with credit card details via an instruction-based
form fill-in. Hence, which mode of interaction is "active" depends on the stage of
the activity that is being carried out.