A schema specifies a set of element names, the names and datatypes of any attributes associated with them, and rules about the contexts in which they may legally appear. A schema for our simple example above will say that elements named <doc>, <p>, <placeName> etc[.] exist. It may also specify that <p> elements may appear within <doc> elements, that <placeName>s may appear within <p>s, that the attribute @n must have a numeric value etc. Note however that an XML schema still has no way of specifying that the tag <placeName> indicates the name of a place, or what we mean by “a place”: such additional semantic constraints must be specified elsewhere, for example by documentation such as that provided by the TEI Guidelines.