Defining a Trigger Two People Would Agree On
Here is a test that costs nothing. Write your entry rule on a piece of paper, hand it to somebody who trades, give them the same chart, and ask them to mark every point where the rule fired. Then compare their marks with yours. Most rules that feel completely clear in the head fail this on the first session they are tried against, and the places they fail are the places that have been quietly costing money.
Ambiguity Hides in Ordinary Words
The usual culprits are adverbs. Decisively, clearly, convincingly, with conviction. Each one sounds like it narrows the rule and none of them can be checked. Two people will not draw the same line between a decisive break and an ordinary one, and neither will the same person on a Monday and on a Thursday.
Nouns can hide just as much. A rule that references the breakout bar assumes everyone agrees which bar that is. A rule that mentions volume confirmation has not said volume of what, measured over what, compared against what. These are not pedantic objections. Each unspecified term is a place where the rule will resolve itself according to whatever you happen to want at the time.
The Four Things a Trigger Must State
A complete trigger definition answers four questions, and most written rules answer only the first. Which level, is the easy one, and it still needs care: the range high measured over which period, and does the period end on a bar boundary or a clock time.
What condition relative to that level, is the second. Touched, traded through, traded through by a stated amount, closed beyond, remained beyond for a stated duration. One of these, named.
Observed on what, is the third. A condition on a one minute bar and the same condition on a five minute bar are different rules. If the condition involves a close, the bar length is part of the definition and not an implementation detail.
And when does the trigger expire, is the fourth, which almost nobody writes down. A break at the very end of the session is not the same opportunity as a break shortly after the range completes, and a rule with no cutoff is a rule that will eventually take one at an hour you never intended to trade.
Write It as a Sequence of Checks
The practical form is a short list of conditions in order, each of which is either true or false when you look at it. Not a paragraph describing the setup, because prose invites interpretation, but a sequence you can run down while the bar is forming.
Ordering matters more than it looks. A rule with three conditions checked in a fixed order can be evaluated the same way every time, and it can be abandoned early when the first condition fails, which saves you from talking yourself into the second. The same three conditions held loosely in mind get weighed against each other, and weighing is where the discretion creeps back in.
The list should be short enough to hold in view. A definition with many clauses is usually one that has been patched after each bad trade, and a patched rule tends to be tuned to the particular losses that prompted it rather than to anything general.
Testing the Definition Against Awkward Cases
Once written, run the rule against the cases that usually cause arguments rather than the clean ones. The break that happens on the very bar the range completes. The break where price is already beyond the level at the moment the range period ends. The second break in the same direction after a first one failed. The break that occurs while a scheduled release is printing.
For each, the rule should produce an answer without you having to think about what you meant. Where it does not, that is the clause to add, and adding it now is much cheaper than discovering it during a session with a position at stake.
Why Precision Is Worth the Trouble
A precisely defined trigger is not necessarily a better trigger. It can be specified exactly and still be a poor rule. What precision buys is the ability to find out.
A vague rule cannot be evaluated, because every disappointing outcome can be attributed to having applied it badly rather than to the rule itself, and every good outcome confirms it. A rule that fires unambiguously produces a record of what it actually did, and that record is the only thing that can tell you whether to keep it. The point of the exercise is not agreement with another trader. It is agreement with yourself, across sessions, when the market is making it inconvenient.