Diazo, previously named xdv, is a general-purpose, open source website theming tool. It is written in Python and generals XSLT. Diazo creates a separation between themes (static HTML) and transformation rules (Diazo’s own domain specific language based in XML), allowing web designers to work on templates in plain HTML, without knowledge of XSLT or special template-related codes. Diazo creates a website with the help of a user-defined rules. The rules file (conventionally named) has directives which, for example, can replace the contents of an HTML node with the content of the content.