operator: starts-with

    description:
        starts-with ket
        returns all relevant kets that start with the given prefix

    examples:
        -- learn some knowledge:
        age |person: Fred Smith> => |47>
        mother |person: Fred Jones> => |Mary>
        age |person: Sam Hughes> => |49>

        -- now ask some questions:
        starts-with |>
            |context> + |person: Fred Smith> + |person: Fred Jones> + |person: Sam Hughes>

        starts-with |person: >
            |person: Fred Smith> + |person: Fred Jones> + |person: Sam Hughes>

        starts-with |person: Fred >
            |person: Fred Smith> + |person: Fred Jones>

    see also:
        rel-kets, guess-ket