Returns TRUE only if there is not a point of geom2 located inside of the geom1 and at least one point is of geom2 is located inside of geom1. So, it will return TRUE if the inside and the edge of geom2 are located completely inside of geom1.

1 geo.contains

    <geom1> *
        <geom1 /> *
    <geom2> *
        <geom2 /> *
    <from table='buildings' alias='a' >
    <where> = 'MACBA'