| ed | (edition) indicates which edition or version the milestone applies to. | 
|  | Datatype: CDATA | 
|  | Values: Any string of characters; usually a siglum conventionally used
for the edition. | 
|  | Default: #IMPLIED | 
|  | Example: | 
| n | (number or name) indicates the new number or other value for the unit which changes
at this milestone. | 
|  | Datatype: CDATA | 
|  | Values: Any string of characters. | 
|  | Default: #IMPLIED | 
| Note | The special value unnumbered should be used in
passages which fall outside the normal numbering scheme (e.g. chapter
heads, poem numbers or titles, or speaker attributions in verse drama). | 
| unit | indicates what kind of section is changing at this milestone. | 
|  | Datatype: CDATA | 
|  | Legal values: | | page | page breaks in the reference edition. |  | column | column breaks. |  | line | line breaks. |  | book | any units termed `book',
`liber', etc. |  | poem | individual poems in a collection. |  | canto | cantos or other major sections of a poem. |  | stanza | stanzas within a poem, book, or canto. |  | act | acts within a play. |  | scene | scenes within a play or act. |  | section | sections of any kind. |  | absent | passages not present in the reference edition. | 
 | 
|  | Default: #REQUIRED | 
|  | Example: | 
| Note | If the milestone marks the beginning of a piece of text not
present in the reference edition, the special value absent
may be used as the value of unit .  The normal interpretation
is that the reference edition does not contain the text which follows,
until the next <milestone>  tag for the edition in question is
encountered. In addition to the values suggested, other terms may be appropriate
(e.g. Stephanus for the Stephanus numbers in Plato). |