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

{{{
[[{.someclass}http://google.com|This is a link with a class attribute "someclass"]]

[[{#someid}http://google.com|This is a link with an id]]

[[{#someid.someclass}http://google.com|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 http://textism.com/tools/textile (although not verbatim)

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