Some ideas for global attributes (id and class). Here is an example usage with link markup:

[[{.someclass}|This is a link with a class attribute "someclass"]]

[[{#someid}|This is a link with an id]]

[[{#someid.someclass}|This is a link with a class and id!]]

The above could be applied to any inline creole (links, bold, italics, etc.). Block markup becomes more complicated: 


|{.someclass} Does this class apply to the table, row, or cell | There doesn't seem to be an easy way |

Paragraphs, on the other hand, are pretty straight forward:

{.indent}Here is my paragraph with class="indent"! 


These ideas come from (although not verbatim)

-- [[StephenDay]], 2008-Sept-15