Canonical S-expressions - Interpretation and Restrictions

Interpretation and Restrictions

While csexps generally permit empty lists, empty atoms, and so forth, certain uses of csexps impose additional restrictions. For example, csexps as used in SPKI have one limitation compared to csexps in general: every list must start with an atom, and therefore there can be no empty lists.

Typically, a list's first atom is treated as one treats an element name in XML.