{
    "query": {
        "@type": "koral:group",
        "operation": "operation:relation",
        "operands": [
            {
                "@type": "koral:span",
                "layer": "c",
                "key": "s"                                
            },
            {
                "@type": "koral:token"             
            }
        ],
        "relType": {
            "@type": "koral:relation",
            "wrap": {
                "@type": "koral:term",
                "foundry": "mate",
                "layer": "d",
                "key": "HEAD"
            }
        }
    },
    "meta": {}
}