Properties, identity and multiple values

world open.
jacob:Person[child -> {joseph, benjamin}; label -> "Jacob"].
?- jacob[child -> ?Child].
?- jacob[child -> {joseph, benjamin}].
expect unknown: jacob[child -> anotherChild].

The variable query returns Benjamin and Joseph as separate bindings. The ground question about both values returns true. Neither question claims that no other child exists.

-> means that a property has a value. It does not promise a single value and it is not assignment. Adding another child preserves earlier children. Repeating the same fact does not create another logical copy.

The braces abbreviate multiple facts; they do not store a list or a set-valued object. They carry no ordering information. Bundles in conditions require all their members. Express alternatives with explicitly grouped OR.

The identifier jacob is different from the label string "Jacob". Labels are human-facing data. Two objects with the same label do not automatically become the same object. Stable identity matters when merging sources and knowledge graphs.

Naming convention

Use descriptive lower-camel-case object and property names, capitalized class names, quoted strings, and ?Name variables. Do not rely on capitalization alone to mark a variable. For an uppercase entity in a value position, use a backtick-delimited identifier. Integers, finite decimal numbers, booleans and strings remain different kinds of values; avoid assuming text-to-number conversion.

Try it

Add another child and rerun the ground question. Why does the answer remain true? What extra assumption would you need to claim the list was complete?