Terminology

Traffical’s dashboard, API, and analyses all use the same small vocabulary for the things a running policy produces and the things an analysis counts. This page defines that vocabulary. Every other page uses these terms in exactly these senses.

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Assignment events

An assignment event is every decision or exposure row produced by a running policy, repeats included. It measures serving volume — not a sample size. Assignment events are the umbrella term. They comprise two kinds:

• Decision event — the SDK resolved an allocation for a unit — the intent-to-treat (ITT) signal, whether or not the unit saw it.
• Exposure event — a unit actually experienced its allocation — the treatment-on-the-treated (TOT) signal.

Both kinds fire automatically. A single unit generates many assignment events over time: every resolution produces a decision event, and every read of a parameter value produces an exposure event (deduplicated within a session). When a surface counts raw event rows without distinguishing the two kinds, that count is a count of assignment events.

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The three counts

Surfaces that report volume use three counts, each strictly smaller than the last: The three form a funnel: assignment events ⊃ unique units ⊃ enrolled units. Deduplicating assignment events by unit key gives you unique units; attributing each unique unit to the allocation of its first assignment — and excluding units seen in more than one allocation — gives you enrolled units.

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Entry points and qualification

An entry point is a reusable, timestamped milestone that determines when a unit qualifies for measurement — reaching checkout, say, rather than merely visiting the site. Its qualification rules are conditions on source-fact dimensions that select which fact rows qualify. When a measurement has an entry point attached, the funnel gains a fourth step: assignment events ⊃ unique units ⊃ enrolled units ⊃ qualified units.

• Qualified units — enrolled units with a qualifying fact at or after first assignment. The analysis sample when an entry point is active.
• Qualification rate — qualified units divided by enrolled units, shown overall and per allocation.
• Time to qualification — how long after first assignment units reach the entry point — the gap between enrollment and qualification, shown as p50/p75/p90.

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Allocations and traffic splits

An allocation is a named bundle of parameter overrides a policy serves, with a share of its traffic. control, treatment, low_price — each is an allocation. Allocation is the canonical noun; other tools call the same thing a “variant” or an “arm”. The traffic split is how a policy’s traffic divides across its allocations — for example, 50% / 50%, or 90% / 10% during a ramp. Percentages on a policy always describe traffic, so they read “traffic” or “traffic split”.

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Decision log vs decision events

These two share a word but have nothing else in common:

• Decision events are runtime data: one row per SDK resolution, the ITT half of assignment events.
• The decision log is the governance audit trail of decision records — approvals, ramps, promotions, guardrail breaches — capturing who did what and why at each lifecycle moment. See the decision log.

A policy serving a million decision events writes no decision records; approving its measurement plan writes one.

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Analysis signal

The analysis signal is which assignment signal an analysis reads:

• Decision events give an intent-to-treat (ITT) analysis: every unit the policy resolved an allocation for counts, whether or not the unit saw it. ITT catches problems that stop an allocation from rendering.
• Exposure events give a treatment-on-the-treated (TOT) analysis: only units that actually experienced their allocation count. TOT measures the effect on units the change really reached.

In warehouse-native mode, an assignment definition declares its Signal — decision or exposure, or mixed when a source_type column is mapped and each row says which kind it is.

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Next steps