<?xml version="1.0" encoding="UTF-8"?>
<flow>
    <chain name="chain1">
        THEN(v.tag("subChain1"));
    </chain>

    <chain name="subChain1">
        THEN(v.tag("subChain2"));
    </chain>

    <chain name="subChain2">
        THEN(a, b);
    </chain>
</flow>