- Sometimes you do not want statements in an SVG file to be executed
- tref text
- Gradients
- Style sheets
- Scripts
- Symbols
- Patterns
- Filters
- You can fudge some of these by having the element invisible
- More sensible to group all referenced items in a defs element
<defs>
- - -
</defs>
Good practice for defs to be higher in the parse tree than the place where it is used
