<s:assert test="@spanTo">The @spanTo attribute of <s:name/> is required.</s:assert>
Schematron
<s:assert test="@spanTo">L'attribut spanTo est requis.</s:assert>
Example
<p>Paragraph partially damaged. This is the undamaged portion <damageSpan spanTo="#a34"/>and this the damaged portion of the paragraph.</p> <p>This paragraph is entirely damaged.</p> <p>Paragraph partially damaged; in the middle of this paragraph the damage ends and the anchor point marks the start of the <anchor xml:id="a34"/> undamaged part of the text. ...</p>
Both the beginning and ending of the damaged sequence must be
marked: the beginning by the damageSpan element, the ending
by the target of the spanTo attribute: if no other
element available, the anchor element may be used for
this purpose.