Not returning properties and/or categories in custom namespaces
I never did! Eventually sort of gave up, though I pop in occasionally to see if anything new has come up. I'll keep an eye on your post!
Sorry to not have better news.
It looks to me like this should be a very simple fix, if I'm reading things right...
First of all, you should switch to using defined constants instead of magic numbers:
## Define namespaces
define( "NS_BLOG", 500 );
...as kgh recommended. Of course, you could just use the magic number 500 in both places, but it's better to use a defined constant to prevent mistakes.
Then register your namespace using the wikilog extension using your defined constant instead of the magic number "500":
Wikilog::setupNamespace(NS_BLOG, 'Blog', 'Blog_talk' );
...i.e., that's the same as writing $wgExtraNamespaces[NS_BLOG] = "Blog";
to declare the new namespace, except it also does some additional setup related to the Wikilog extension, and ensures you declare the namespace correctly.
Now your namespace is set up, set it to allow semantic properties by adding
$smwgNamespacesWithSemanticLinks[NS_BLOG] = true;
...hope that helps.