SVG 1.1 is quite a low-level standard. The intention early on was to produce another constraint-based standard, SVG 2.0, that sat on top of SVG 1.1 providing a better interface to the SVG content.
Without a higher-level graphics standard, it is necessary for many applications to define the graphics content above SVG 1.1 and to transform it down into SVG 1.1. Being an application of XML, the obvious choice is to define the higher level graphics in XML and transform it into SVG. An excellent example of this in terms of accessibility is the GRASS system of Zaineb ben Fredj.
This introduction to XSLT concentrates on XSLT 1.0 and the functionality that has been used to transform XML into SVG animation.