corner-lines.xml

<svg>
    <defs>
      <marker id="arrow" refX="1" refY="0.5" orient="auto-start-reverse" markerWidth="5" markerHeight="5" viewBox="0 0 1 1">
        <path d="M 0 0 1 0.5 0 1" style="stroke-width: 0.2;"/>
      </marker>
    </defs>
    <style>
        <![CDATA[
            rect { fill: white; stroke: black; stroke-width: 0.1px; }
            line, polyline { stroke-width: 0.2px; stroke: black; fill: none; }
            text { font-size: 3px; dominant-baseline: central; text-anchor: middle; }
            .outline { fill: lightblue;}
        ]]>
    </style>

    <rect xy="3 18" wh="24 27" class="outline"/>
    <rect xy="10 20" wh="10" text="a" id="a"/>
    <rect xy="5 35" wh="8" text="b" id="b"/>
    <rect xy="20 33" wh="5" text="c" id="c"/>
    <polyline start="#a@b" end="#b@t" corner-offset="25%" marker-end="url(#arrow)"/>
    <polyline start="#a@r" end="#c@t" marker-end="url(#arrow)"/>
    <polyline start="#a@l" end="#b@l" corner-offset="1.5" marker-end="url(#arrow)"/>
    <line start="#b@r" end="#c@l" marker-end="url(#arrow)"/>
</svg>