Use of empty tags in docbook xml?

Hi List.

Is there a general opinion on using empty tags in docbook xml?

e.g., occasionally in a 3-col table, one cell doesn't require an entry,
so I leave an empty <entry> tag. This has popped up in other places as
well, but I'm just wondering if there is a preferred method for dealing
with this.

Is there a non-displayable character I can use, perhaps?

thanks for any suggestions.
-- 
David O'Brien		Ph: +61 7 3514 8189
Content Services	Mb: +61 411 760 216
Red Hat Asia Pacific	Fx: +61 7 3514 8199

SIP:
1.866.546.8970 (866LINUX70)
or
+1.480 718.6000, X81 51143