# Guidelines

### Processing Rules

* **Purpose:** Take the incoming `contextData` aliases and assign them to concrete eVars, props, or events so they surface in reporting.
* **Order matters:** If you overwrite variables in multiple rules, be mindful of rule execution order—later rules cannot recover the original value if overwritten incorrectly. 
* **Guard against empty overwrites:** Only apply overwrites if the incoming value is present to avoid unintentionally blanking fields.
* **Friendly naming:** Use consistent human-readable labels (e.g., “LiSA Session ID”, “LiSA Media Type”) to reduce cognitive load for analysts.

### Naming Conventions

* Prefix mapped variables with a clear namespace like “LiSA” in the friendly label.
* Use semantic event names in Adobe (e.g., `event1` = “Playback Started”, `event2` = “Product Click”) and document their mapping for internal consistency.

### High-Cardinality Caution

Some values (UUIDs like `eventId`, `visitorId`, `mediaItemId`) are high-cardinality. Sending these directly into ad-hoc breakdowns can degrade performance or produce unwieldy reports.

#### Best practices:

* Use classification rules to derive human-friendly buckets (e.g., grouping product IDs into content categories) without changing the raw alias.
* Limit how many unique dimension items a given report expands on; apply filters or sample intelligently.
* Dual-capture when needed: e.g., have a UUID in an eVar for attribution but also capture a lower-cardinality derived attribute (like product category) for easy breakdowns.