Filtering FamilyInstances by multiple categories via FamilySymbols

This filter combines an inclusion list with the two-step relationship pattern to select placed elements across multiple categories.

(
  /* Category inclusion */
  $CategoryInclusion := ["OST_Doors", "OST_Windows"];

  /* Filter FamilySymbols by category */
  $familySymbols := $[
    type = "FamilySymbol"
    and values.category.label in $CategoryInclusion
  ].id;

  /* Filter FamilyInstances by their FamilySymbol */
  $[
    type = "FamilyInstance"
    and parent.id in $familySymbols
  ].{
    "id": id,
    "type": type,
    "name": name,
    "parent": parent.id
  }
)

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What this filter does

"Select all placed door and window elements by first selecting the relevant types, then selecting all instances that use those types."

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Why the two steps are necessary

Category data lives on FamilySymbol, not on FamilyInstance. Filtering instances directly by category is fragile — the correct approach is always:

1. Filter symbols by category → collect their IDs
2. Filter instances where parent.id is in that set

This pattern is correct for any rule that applies to placed elements of specific categories. See Two-Step Filtering for the full explanation.

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Typical use cases

Use this structure for rules like:

• "All placed doors and windows must have a Mark"
• "Door and window instances must be on a valid level"
• "No placed element in these categories may have an empty Assembly Code"

Any rule that combines multiple categories with instance-level validation starts here.