Limit class names to not contain spaces
Signed-off-by: martin f. krafft <madduck@madduck.net>
diff --git a/doc/source/concepts.rst b/doc/source/concepts.rst
index 67816d8..76b5818 100644
--- a/doc/source/concepts.rst
+++ b/doc/source/concepts.rst
@@ -25,6 +25,8 @@
A class consists of zero or more parent classes, zero or more applications,
and any number of parameters.
+A class name must not contain spaces.
+
A node is almost equivalent to a class, except that it usually does not (but
can) specify applications.