Revision control
++ <svg width="400" height="400" viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
++ <defs>
++ <!-- Arrowhead marker definition -->
++ <marker
++ id="arrow"
++ viewBox="0 0 10 10"
++ refX="5"
++ refY="5"
++ markerWidth="6"
++ markerHeight="6"
++ orient="auto-start-reverse">
++ <path d="M 0 0 L 10 5 L 0 10 z" />
++ </marker>
++
++ <!-- Dot marker definition -->
++ <marker
++ id="dot"
++ viewBox="0 0 10 10"
++ refX="5"
++ refY="5"
++ markerWidth="5"
++ markerHeight="5">
++ <circle cx="5" cy="5" r="5" fill="red" />
++ </marker>
++ </defs>
++
++ <!-- Coordinate axes with an arrowhead in both directions -->
++ <polyline
++ points="10,10 10,90 90,90"
++ fill="none"
++ stroke="black"
++ marker-start="url(#arrow)"
++ marker-end="url(#arrow)" />
++
++ <!-- Data line with polymarkers -->
++ <polyline
++ points="15,80 29,50 43,60 57,30 71,40 85,15"
++ fill="none"
++ stroke="grey"
++ marker-start="url(#dot)"
++ marker-mid="url(#dot)"
++ marker-end="url(#dot)" />
++ </svg>