ACDD checks for "acknowledgement", IOOS checks for "acknowledgment"
When running "cchecker.py -t acdd:latest", it looks for either "acknowledgment" (US spelling, from deprecated UDDC convention) or "acknowledgement" (UK spelling, as required by superceding ACDD convention). However, when running "cchecker.py -t ioos:latest", the test only looks for the deprecated US spelling. It should either look for both spellings like the ACDD test or switch to the UK spelling as currently required.

Example:
http://www.pacioos.hawaii.edu/archive/WQB04agg/WQB04agg.2010.nc

Snippet for cchecker.py output:

Platform Sponsor                       :3:     0/ 1 : Attr 'acknowledgment'
                                                      (IOOS concept: 'Platform
                                                      Sponsor') not found in
                                                      dataset
diff --git a/compliance_checker/ioos.py b/compliance_checker/ioos.py
index ba292ba..115d3a2 100644
--- a/compliance_checker/ioos.py
+++ b/compliance_checker/ioos.py
@@ -52,7 +52,7 @@ class IOOSNCCheck(BaseNCCheck, IOOSBaseCheck):
         Check all global NC attributes for existence.
         """
         return [
-            self._has_attr(ds, 'acknowledgment', 'Platform Sponsor'),
+            self._has_attr(ds, 'acknowledgement', 'Platform Sponsor'),
             self._has_attr(ds, 'publisher_email', 'Station Publisher Email'),
             self._has_attr(ds, 'publisher_email', 'Service Contact Email', BaseCheck.MEDIUM),
             self._has_attr(ds, 'institution', 'Service Provider Name', BaseCheck.MEDIUM),
['compliance_checker/ioos.py']