After consulation with MH, I've changed the bookmark file schema so that, instead of an "id" attribute, bookmark elements now have an "n" attribute. This change, in turn, allows for the value of the attribute to be purely numeric, rather than being prepended with a "b". I made this change to make sorting the bookmarks by unique identifier easier, since string values (b1, b2, etc) can't be sorted by numeric value (1, 2, etc).