SVG definition inheritance - svg

Question

Please look at eaExperiment. I want to make a definition which takes StartArrow definition and rotates it by 180 degrees.
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:cc="http://creativecommons.org/ns#" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg" width="450" height="400" version="1.1">
<style type="text/css">
<![CDATA[
rect {fill:white; stroke: black; stroke-width: 1;}
text {fill: black; font-family: sans-serif; font-size: 10pt}
line {stroke:black; stroke-width:2}
]]>
</style>
<defs>
<marker orient="auto" refY="0.0" refX="0.0" id="StartArrow" style="overflow:visible;">
<path style="fill-rule:evenodd;stroke-width:0.625;stroke-linejoin:round;stroke:#000000;stroke-opacity:1;fill:#000000;fill-opacity:1" d="M 8.7185878,4.0337352 L -2.2072895,0.016013256 L 8.7185884,-4.0017078 C 6.9730900,-1.6296469 6.9831476,1.6157441 8.7185878,4.0337352 z " />
</marker>
<use id="eaExperiment" href="#StartArrow" transform="rotate(180)" />
<marker orient="auto" refY="0.0" refX="0.0" id="EndArrow" style="overflow:visible;">
<path style="fill-rule:evenodd;stroke-width:0.625;stroke-linejoin:round;stroke:#000000;stroke-opacity:1;fill:#000000;fill-opacity:1" d="M 8.7185878,4.0337352 L -2.2072895,0.016013256 L 8.7185884,-4.0017078 C 6.9730900,-1.6296469 6.9831476,1.6157441 8.7185878,4.0337352 z " transform="rotate(180)" />
</marker>
<svg id="Box">
<rect width="100" height="85" x="1" y="1" />
<text x="5" y="20">The box</text>
<svg x="10" y="25">
<rect width="70" height="50" x="1" y="1" />
<text x="5" y="20">Box</text>
<text x="5" y="40">Contents</text>
</svg>
</svg>
</defs>
<svg>
<svg x="10" y="120">
<rect width="100" height="50" x="1" y="1" />
<text x="5" y="20">Data</text>
<text x="5" y="40">source</text>
</svg>
<svg x="150">
<use href="#Box" y="1" />
<use href="#Box" y="100" />
<use href="#Box" y="200" />
</svg>
<svg x="300" y="120">
<rect width="100" height="50" x="1" y="1" />
<text x="5" y="20">Database</text>
<text x="5" y="40">server</text>
</svg>
<line x1="100" y1="120" x2="148" y2="40" style="marker-end:url(#EndArrow)" />
<line x1="110" y1="150" x2="147" y2="150" style="marker-end:url(#EndArrow)" />
<line x1="100" y1="170" x2="148" y2="240" style="marker-end:url(#EndArrow)" />
<line x1="254" y1="40" x2="297" y2="120" style="marker-start:url(#StartArrow); marker-end:url(#EndArrow)" />
<line x1="250" y1="150" x2="297" y2="150" style="marker-start:url(#eaExperiment); marker-end:url(#EndArrow)" />
<line x1="250" y1="240" x2="297" y2="170" style="marker-end:url(#EndArrow)" />
</svg>
</svg>
I am definitely doing it wrong, but what is the right way?

Answer 1

You need separate <marker> elements, but their content can be reused with <use> elements. For example like this:
<defs>
<path id="arrow" style="fill-rule:evenodd;stroke-width:0.625;stroke-linejoin:round;stroke:#000000;stroke-opacity:1;fill:#000000;fill-opacity:1" d="M 8.7185878,4.0337352 L -2.2072895,0.016013256 L 8.7185884,-4.0017078 C 6.9730900,-1.6296469 6.9831476,1.6157441 8.7185878,4.0337352 z " />
<marker orient="auto" refY="0.0" refX="0.0" id="StartArrow" style="overflow:visible;">
<use xlink:href="#arrow" />
</marker>
<marker orient="auto" refY="0.0" refX="0.0" id="EndArrow" style="overflow:visible;">
<use xlink:href="#arrow" transform="rotate(180)" />
</marker>
</defs>
(While the use of the xlink namespace with href is deprecated and also from a practical perspective no longer needed in current browsers, I tend to still use it for the sake of other renderers, Inkscape for example.)