To find out whether a resource has been modified since the last download, OWS sends a HTTP HEAD request to the server and expects to receive the last modified timestamp of the resource on the server.In order to facilitate caching of resources by OWS it is necessary that the server from where the resources are downloaded is configured to respond to HTTP HEAD request.In case the server is not configured to respond to HTTP HEAD request, OWS will not be able to determine the last modified timestamp of the resource and will go ahead and download the resource.