Add os-specific sub-classes and have profile::base use case $::kernel

site/profile/manifests/base.pp

@@ -1,5 +1,14 @@
+# Base profiles include all the classes that should be included on all nodes.
+# For cross-platform compatibility, this is broken up into platform-appropriate
+# subclasses.  This class applies the appropriate base profile based on the
+# $::kernel fact.
+
 class profile::base {
 
-  #the base profile should include component modules that will be on all nodes
+  # Include a platform-appropriate base profile
+  case $::kernel {
+    'Linux':   { include profile::base::linux   }
+    'windows': { include profile::base::windows }
+  }
 
 }

site/profile/manifests/base/linux.pp

@@ -0,0 +1,6 @@
+# A 'base' profile should include component modules that will be on all nodes
+# of a particular operating system.
+
+class profile::base::linux {
+
+}

site/profile/manifests/base/windows.pp

@@ -0,0 +1,6 @@
+# A 'base' profile should include component modules that will be on all nodes
+# of a particular operating system.
+
+class profile::base::windows {
+
+}