puzzlement over prefix expansion

I'm having trouble understanding rdf prefix expansion.

Below is a mass-o-code. According to my feeble mind's understanding it should work, but
it doesn't, so obviously I'm autobogotified.

Forgive the length, but I figured better that than missing something relevant.

I'm trying to generate a turtle file that represents some info I already have as prolog facts
(thats whats in floblocks).  I'm having trouble with rdf_meta not working properly - querying
convert('test.ttl'). 
results in it running down to the error, where it throws an error, expecting an atom and getting
flo:inputFor
which is apparently   ':'(flo, inputFor)

Note that it's obviously the rdf_meta being ignored somehow, since items in add_rdf are being converted properly.
changing one of the r's in the rdf_meta to rdf generates an error, so apparently the rdf_meta declaration is indeed being
interpreted somehow.

:- module(converter, [convert/1]).
/** <module> Non automagic code for making the rdf

*/
:- use_module(floblocks).

:- use_module(library(semweb/rdf_db)).
:- use_module(library(semweb/rdf_turtle_write)).
:- use_module(library(semweb/rdfs)).

:- rdf_register_prefix(flo, 'http://www.friendularity.org/ontology/flo#').


convert(Outfile) :-
setof(BlockType, Section^section(BlockType, Section), BlockTypes),
add_rdf(BlockTypes),
write_rdf(Outfile).

add_rdf([]).
add_rdf([H|T]) :-
rdf_global_id(flo:H, HGlobal),
rdf_assert(HGlobal, rdf:type, flo:'BlockType'),
subsection(H, SubSection),
rdf_assert(HGlobal, flo:subsection, literal(SubSection)),
section(H, Section),
rdf_assert(HGlobal, flo:section, literal(Section)),
description(H, Desc),
rdf_assert(HGlobal, rdfs:comment, literal(Desc)),
rdf_assert(HGlobal, rdfs:label, literal(H)),
visual_style(H, Style),
rdf_assert(HGlobal, flo:visual_style, literal(Style)),
inputs(H, InputList),
input_types(H, InputTypeList),
% call is here
assert_rdf_list(HGlobal, flo:inputFor, flo:inputName, InputList,
     flo:inputType, InputTypeList),
outputs(H, OutputList),
output_types(H, OutputTypeList),
assert_rdf_list(HGlobal, flo:outputFor,
flo:outputName, OutputList,
flo:outputType, OutputTypeList),

add_rdf(T).

:- rdf_meta assert_rdf_list(o, r, r, +, r, +).

assert_rdf_list(_, _, _, [], _, _).
assert_rdf_list(Subj, PredLinkingSubj, Type1, [required(H1)|T1], Type2, [H2|T2]) :- !,
rdf_bnode(BNode),
% Yells that PredLinkingSubj is flo:inputFor, isn't an atom here   <=== THE ERROR
rdf_assert(BNode, PredLinkingSubj, Subj),
rdf_assert(BNode, Type1, literal(H1)),
rdf_assert(BNode, Type2, literal(H2)),
rdf_assert(Subj, flo:requiresInput, BNode),
assert_rdf_list(Subj, PredLinkingSubj, Type1, T1, Type2, T2).
assert_rdf_list(Subj, PredLinkingSubj, Type1, [optional(H1)|T1], Type2, [H2|T2]) :- !,
rdf_bnode(BNode),
rdf_assert(BNode, PredLinkingSubj, Subj),
rdf_assert(BNode, Type1, literal(H1)),
rdf_assert(BNode, Type2, literal(H2)),
rdf_assert(Subj, flo:optionalInput, BNode),
assert_rdf_list(Subj, PredLinkingSubj, Type1, T1, Type2, T2).
assert_rdf_list(Subj, PredLinkingSubj, Type1, [H1|T1], Type2, [H2|T2]) :-
rdf_bnode(BNode),
rdf_assert(BNode, PredLinkingSubj, Subj),
rdf_assert(BNode, Type1, literal(H1)),
rdf_assert(BNode, Type2, literal(H2)),
rdf_assert(Subj, flo:optionalInput, BNode),
assert_rdf_list(Subj, PredLinkingSubj, Type1, T1, Type2, T2).


write_rdf(Outfile) :-
rdf_save_turtle(Outfile, []).


A vastly puzzled noobie-to-semweb Annie bangs head against desk