You've been discussing  how SFG analyzes these sentences:
>> >        a) Bob likes the decision to acquit the President
>> >        b) The decision pleases Bob.

SFG describes sentences as consisting of participants, processes, and
circumstances.
Participants are traditional subjects, direct objects, and indirect objects
as well as noun phrases and clauses that function in these roles.  
Processes are traditional verbs.  They come in different types.  The
largest category is material processes, which have Actors as Subjects and
Goals as objects.  Other categories are mental and existential.  
Circumstances are conditions, often optional, of all types, mainly and
usually our adverbials.
(SFG does not analyze vocatives and interjections syntactically.)

Beyond syntax, English  provides choices of different Subjects and Themes,
which allow us to tailor the statements to suit the contexts and cohesive
patterns: one way for a political discussion and another way to discuss our
friend.  SFL has a lot to say about those patterns, but those are other
issues.  I assumed that syntax was the issue here.     

        So let's look at finer details in SFG grammar. It distinguishes
different syntactic patterns for different types of processes.  The
processes under discussion are mental processes. One characteristic of
mental processes is that their unmarked present tense is the simple
present, not the two-word present that is common for material processes 
(Bob likes..., not Bob is liking...).  Another characteristic is that they
cannot be probed with "do."  More relevantly, in mental processes at least
one participant is treated as endowed with consciousness, and the other
participant can be either a thing or a fact.  The participants in mental
processes are called Sensers and Phenomena.  They are bidirectional. In
this case, in either order, Bob is a Senser and the decision is a
Phenomenon.  

>> >        a) Bob likes the decision to acquit the President
Bob is the Sensor, likes is the affective mental process, and decision is
the Phenomenon.
and
>> >        b) The decision pleases Bob.
The decision is the Phenomenon, pleases is a different affective mental
process, and Bob is the Sensor.

        Halliday discusses sentences very much like this pair on pages
112-119 of the second edition of Introduction to Functional Grammar. 
Please correct me if I have oversimplified or misinterpreted him.

Carolyn Hartnett

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