Misunderstanding The System Network

Fawcett (2010: 64n):

In any case, an adequate model of the full process of generation requires other ways of modelling decision-making in the higher stages of planning. System networks can be regarded as a special type of 'decision tree' that is incorporated within the semiotic system of language itself.

Blogger Comments:

[1] This is a bare assertion, unsupported by argument or evidence.

[2] To be clear, system networks do not model decision making, and thus there is a very important sense in which a system network is not a decision tree:

A decision tree is a decision support tool that uses a tree-like model of decisions and their possible consequences, including chance event outcomes, resource costs, and utility. It is one way to display an algorithm that only contains conditional control statements.

A system network does not represent a sequence of decisions. A system network systematises the relations between options in terms of types of expansion:

• delicacy = elaboration
• disjunction = extension: alternation
• conjunction = extension: addition
• entry condition = enhancement: condition
• realisation statement = elaboration (+ identifying)

For instance, a lexical item is not the output of a sequence of decisions.  A lexical item realises all the relations between all of the features that specify it, from the most general systems of the grammar to their most delicate elaboration.