Specify xacro properties in launch file

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I am working on ros-fuerte-gazebo. I have a world in which I want to spawn doors to different rooms.

Is there a way to specify the values for <xacro:property> tags in launch file ? I want to use a single *.urdf.xacro file using different values for the same property. Is it possible ?

For eg.: In door.urdf.xacro

<xacro:property name = room value = "workroom" />
<link name = "${room}_door">
....

I would like to specify the value "workroom" for the property room in the launch file so that I can use the same *.urdf.xacro file for all the rooms in my gazebo world (kitchen, bedroom etc..). I know I can use TinyXML but it will be easier and simpler if I can specify the properties in launch file. Or is there any other way out ?

Thanks!

PS: I know this is more a ros question than a gazebo question. I am posting here hoping some gazebo enthusiast would help me out.