You might also consider the links(). It works as an action to create a set of (attribute) values - default being $Name - of each matching note.

The #linkedTo/#linkedFrom special queries have an optional second parameter, 'Type', allowing you to tighten the match to a single link type.

When testing/researching links for the above don't forget that you can turn each link type off individually via the LinkTypes palette (Cmd+2). Also, the Path view (Cmd+Shift+P) allows you to see all notes linked by a given link type (albeit both source & sink without polarity). Raodmap (Cmd+Opt+R) allows links to be navigated and all inbound outbound links are shown (withuot link types). Browse links shows all outbound links. Lots of slightly overlapping tools.

Not time to build tests now but the above should help give some start points.

Re-read the notes on #linkedTo/#linkedFrom and you'll see the target is a single note. I assume you're not trying to link to a note called "*"? Usage:

#linkedTo("some note",agree)
#linkedFrom("another note")

A note's name can be substituted for by any item object.

#linkedTo("some note","custom type")

If you delete agent #1 do the others work? What is the query for agent #1?

Well, that weird agent behavior seems to have resolved itself.

Thanks much for your help, Mark!

I'm getting encouraging results from using the links() operator.

My little testing ground TBX has three User attributes:
Action (boolean)
OpenPrecedent(boolean)
MyPrecedent(set)

- the Rules for my Task prototype are looking like this:

OpenPrecedent=links.inbound.antecedent.Action;
if($OpenPrecedent) {Action=False};
MyPrecedent=links.inbound.antecedent.Name;

I'm still tinkering to figure out if I want to query from Action or OpenPrecedent, or both, or what, when I collect tasks.

No doubt. Thanks for the pointer - I'll check out that section.

The way I'm working at it now, there are no attempted wildcard searches.

The Tbref that Mark A. referred me to on the #linkedTo syntax does seem to indicate that w*ldcards are ok in queries using #linkedTo and From.

What are IIRC prototpes? What's an 8-based scope of search?

Thanks!

OK, I've continued tinkering for a while now. I'm learning a lot!

And making progress...

But right now I can't figure out from the available reference material if I'm using terms correctly or not, or if it's something else that's stopping me. So it seems like a good time to post.

Here's the idea:
(1) Sequential Tasks are connected, in their required order of doing, by links of a type called "antecedent".
(I.e. each task has a link that points to the task that comes after it, if there is one.)
(2) Through rules, task-notes will know if there is an undone task "upstream" from them. I'm calling an undone upstream task an "open precedent."
(3) Tasks-notes automatically set their Action attribute to false when they have an open precedent, so they won't get swept up by Context agents. Thus, the GTD maxim to focus only on the very next action is achieved. Or at least supported...

Here is the chunk of rules that I'm using, with **annotations**.
Code:

PrecedentValues= links.inbound.antecedent.Action;
**This populates a set attribute with the Action status of any preceding tasks**
if(PrecedentValues(true)){OpenPrecedent=true};
**This is meant to translate the set to a Boolean attribute - it doesn't seem to work.**
PrePrecedentValues=links.inbound.antecedent.OpenPrecedent;
If(PrePrecedentValues(true)){OpenPrecedent=true};
**These two lines are meant to ensure that the existence of an OpenPrecedent in the task sequence cascades downstream.**
if((PrePrecedentValues!(true)&PrecedentValues!(true))){OpenPrecedent=false};
**This last line is meant to reset OpenPrecedent to false when upstream tasks are completed.**
MyPrecedents= links.inbound.antecedent.Name;
**And this rule, which works great, fills a set attribute with the names of the immediate upstream tasks.** 

Here is a copy of the little tester TBX I've been tinkering on:
Sequence]Working.tbx (39.14 KB)

If anyone is able to help, I'll be eternally grateful.

I think this sequential task stuff is important for the TBX/GTD community, as well.

Thanks!