Use of Axis in data-table for categorizing cells

As I understand, it makes sense to associate a single concept with a particular table header (th) cell  using the id and axis  for the cell. While reading the specs for the axis attribute (HTML  4.01 specs)I was perplexed by the statement:
"The value of this attribute is a comma-separated list of category names."
http://www.w3.org/TR/html401/struct/tables.html#adef-axis
 How is it possible to associate more than one concept with a  single cell with one id attribute? See the given example for instance:
 <TH id="a2" axis="expenses">Meals</TH>
  So any data cell that refers to  this cell in its headers attribute (headers=a2") will categorize this data cell as Meals. One cannot  use the same a2  reference for another data cell and expect it to be related to  anything other than meals. Whatever is enclosed within quotes following axis= is interpreted as a single concept  even if two words are separated by a comma.
  1. So is this  an error in the specs?
  2. The specs for  headers attribute (in the HTML specs) say that multiple cell-names (referencing id values of table header cells) should be separated by  a space.  Assistive technologies (like JAWS and HPR) have in fact implemented this and work correctly when a space is used as a separator.... and a comma separator does not   produce expected results. The question is: mostly programmers are used to comma as a separator and specifying a space as the legal separator makes the specs  inconsistent. (For axis it says comma is the separator.) Additionally, there is a problem ifthe id value itself contains a space like in  
  id="office stationery".
  Thanks,
  Sailesh Panchang
  Senior Accessibility Engineer 
  Deque Systems,11180  Sunrise Valley Drive, 
  4th Floor, Reston VA 20191
  Tel: 703-225-0380 Extension 105 
  E-mail: sailesh.panchang@deque.com
  Fax: 703-225-0387
  * Look up <http://www.deque.com> *