Clark name

A Clark name is a way of unambiguously representing a qualified name (see XML) as a string. It consists of the namespace name in curly braces followed immediately by the local name. For example, the Clark name for the DocBook para element is: “{}para”.

hamburger menu

The “hamburger menu” or “hamburger button” is the name for the “☰” icon often used to indicate a menu of choices.

intrinsic size

The intrinsic size of an object is it’s actual size, measured in absolute units, usually pixels. The stylesheets rely on extension functions to obtain the intrinsic size of objects; if the extension functions aren’t available or the image format is not recognized, no intrinsic size will be known.

is true

XPath defines a boolean type, xs:boolean, that is either true or false. But for the purpose of passing parameters to the stylesheet at runtime, whether it’s from the command line, from a configuration file, or through some other means, it’s often more convenient to pass string values. This saves the user from having to use whatever extra syntactic mechanisms would be required to identify the type of the variable.

To this end, many “boolean” parameters are actually strings. A string value is true if it consists of one of the strings “true”, “yes”, or “1”.


In this guide, the term “object” is used to refer generally to any image, video, or audio media element. They have a width and a height but no useful internal structure from the perspective of the stylesheets.


Processing instructions (see XML) have no internal structure. The stylesheets interrogate the db processing instruction to determine formatting properties for a number of different elements.

In order to make it easy to consistently specify different properties, the value of the processing instruction is parsed as if it contained attributes. These pseudo-attributes must consist of a name, followed by “=”, followed by a quoted string.