malloy-document

Documenting a Malloy Model

Add #(doc) tags to describe sources and fields in plain language so they are easy to find and understand:

Tag	Purpose	Goes on
#(doc)	Plain-language description for natural-language search	source, dimension, measure, view, join
#(filter)	Deprecated, prefer given:. Parameterizable filter (runtime/modeling concern, see malloy-model)	source

#(doc) is a standard Malloy annotation. It documents a field or source with a human-readable description that downstream tools can surface and search against.

#(doc) Tag

Add before any source, dimension, measure, view, or join. When multiple fields share a keyword, use it once as a block header. Tags and field names are indented under the keyword; tags go on the line(s) directly above the field they annotate.

Tag ordering (when a field has multiple tags): #(doc) → render tags (# currency, # label, etc.) → field name. Separate each field group with a blank line:

#(doc) Customer who placed the order
join_one: users with user_id

dimension:
  #(doc) Date the order was placed (UTC)
  order_date is created_at::date

measure:
  #(doc) Total revenue from all orders in USD
  # currency
  revenue is sum(total)

Writing Doc Strings for Retrieval

Doc strings power natural-language search: users type plain-English questions and the system matches against your #(doc) strings. Write descriptions that match how analysts would search:

• Include business meaning, not code mechanics: what it represents, not how it's implemented
• Include units (USD, count, percentage): a unit is part of what a number means. For counts, name the unit being counted and say whether it counts distinct entities or events: "total students enrolled" on a subject×term-grain measure counts enrolments, not students, and a student taking four subjects counts four times. If the model cannot answer the distinct-entity version, say so in the doc.
• List a categorical field's values only while the list stays short (roughly ten or fewer). A handful of values makes a description concrete; past that, say what the field captures instead, because the dump crowds out the meaning and goes stale the moment someone adds a value. Treat ten as a rule of thumb, not a hard cap.
• Avoid Malloy jargon: never use "filterable", "groupable", "dimension", "measure", "aggregation"