Attribute list for the <milestone-start> and <milestone-end> elements
The attributes are the same for the start and end elements because existing common practice varies as to which element has the explanatory data and whether both elements are linked to each other or only the start to the end. If creating these from scratch for a book, where there is a choice, best practice is to place the rationale on the start element and to link start to end and end to start.
<!ENTITY % milestone-atts
"id ID #IMPLIED
rationale CDATA #IMPLIED
rid IDREF #IMPLIED" >phrase.ent