On Wed, 01 Dec 2004 21:57:06 +0100, Ekim wrote:

> I have got an element "sensor":
> <!ELEMENT sensor ((longitude, latitude) | (direction, speed))>
> 
> This element has an attribute "type": <!ATTLIST sensor type (GPS | WIND)
> "GPS">
> 
> My question now is, if it is possible that the sub-elements of "sensor"
> are "longitude, latitude" only in the case when the type-attribute =
> "GPS". When the type-attribute = "WIND", the sub-elements shall exactly be
> "direction, speed".

No, it is not possible.

A lot of the time, a "type" attribute is a good indication of a flawed
design, typically where the element type - hey, note that word! - is too 
general for the intended structural purpose.

You can have what you want by replacing the "sensor" element type, which
is too general, with two more specific element types, e.g.

  <!ELEMENT gps-sensor (longitude, latitude) >
  <!ELEMENT wind-sensor (direction, speed) >

And wherever 'sensor' appears in a content model, replace it with 

   sensor => (gps-sensor | wind-sensor)

Note also that you can dispense with the 'type' attribute, too.