Igor Query

An Igor query is a relationship pattern in which one of the subject patterns may be preceded by a subject marker.

This scary-looking syntax includes only three paths. I'll highlight each path in black.

In the first path, the Igor query has no subject marker.

In the second path, a subject marker is prepended to the first subject pattern in the relationship pattern:

In the third path, a subject marker is prepended to some subject pattern other than the first:

Explanations of subject markers TBD.

The Subjects of a Pattern

• The subjects of an instance pattern are the views that match the instance pattern.
• By default, a relationship pattern's subjects are the subjects of the last pattern in the relationship pattern. Subject markers and branch patterns override this default.
• If a pattern in an Igor query is marked with a subject marker, the Igor query's subjects are the subjects of the marked pattern.
• A branch pattern's subjects are the subjects of the first pattern in the enclosed relationship pattern.

Further explanation with examples TBD.

Subject Marker

A subject marker is a dollar sign ($) prepended to an instance pattern or branch pattern. A subject marker marks a pattern as the subject of the enclosing Igor query.

• $s1 s2 — matches a view s1 that has a descendant view s2.

At most one subject marker is allowed in an Igor query.

Subject markers are not allowed inside branch patterns.