For released artifacts, if I have an entry in the cache, I wouldn't want Ivy to check the repo that it was obtained from. However, for SNAPSHOT artifacts, I need Ivy to check to see whether the artifact on the repo is newer than what I have in the cache. In the Ivy documentation, in a subsection titled "Changes in module metadata" there is a reference to a property called "checkModified" which goes on the resolver definition. This seems to be what I need.
However, when I tried to add 'checkModified="true"' on my "ibiblio" element that points to our intranet Nexus repository, it failed with: "ivysettings.xml: no set method found for checkModified on class org.apache.ivy.plugins.resolver.IBiblioResolver"