Just to add to what's been said already:

>  As I think you've realized, once features are read, they generally
>  stay in that order throughout the workspace; that's quite important
>  for some formats such as DGN, and some transformers work better when
>  you can assume features are processed in this order. You can change
>  the order using a Sorter, and of course merging/splitting streams of
>  data may cause a change of order.

This is completely correct.  And unlike the Ghostbusters, there's no
danger when you "cross the streams"
(http://tinyurl.com/rt5jp) 

Most commonly, the Sorter is used to do a meaningless sort if all you
want to do is stop-up a stream for some reason.  GlobalVariable
setting/retrieving is also a way to do something like what the
feature-merger can do -- in the example here, the roads themselves
could go through straight away unfettered, and after the filtering, a
global variable could be set to YES for each NODE ID that should be
saved.  Simultaneously, the  nodes would go into a sorter to STOP them
up, and when they came out (which would happen after all the input
data of any kind was read) then a global variable retriever could be
used to check if there was a global variable for the node id with the
value yes.  Okay, it is tricky to set this up in workbench 'cause I
just checked and the global variable names are asked for as if they
are constants, but you can go behind FME's back and use
&ATTRIBUTE_NAME in place of where the constant should have been to set
a global variable whose name is taken from the value of an attribute,
in this case, called ATTRIBUTE_NAME.

But why I was really responding to this post was so that I could point
out one other obscure thing, that rarely should matter, but is
interesting nonetheless.

If you have multiple connection links coming out of a single output
port of a transformer or source feature type, the FIRST one you
connected or drew is the first one that will fire, that is, where data
will flow.  And as soon as that feature has gone as far as it can, the
second link drawn will have a feature sent down it.  Normally one
would not care about this but there are some obscure cases where it
can make a difference (such as when writing to tables that have
foreign key constraints on them, or when global variables are
involved).

Good questions.

Dale





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