Parsing and correctly mapping rdf

We're trying to map an incoming feed that looks like the preview below through Common Parser. Looks fine to me. But when we attempt to map any of the rdf namespace values, they fail. Other namespace values map fine. What am I missing? Thanks!

Array
(
    [title] => Doing More With Less: A Conversation With Kerry Weems [WEB EXCLUSIVES] 
    [description] => The Centers for Medicare and Medicaid Services (CMS) is a resource-starved agency with few friends on Capitol Hill. From the perspective of its last administrator, neither Congress nor the White ...
    [options] => Array
        (
            [guid] => http://content.healthaffairs.org:80/cgi/content/short/28/1/w29?rss=1
            [timestamp] => 1230796800
            [original_author] => Array
                (
                    [0] => Guterman, S.
                    [1] => Davis, K.
                    [2] => Schoenbaum, S.
                    [3] => Shih, A.
                    [4] => Levin, R.
                    [5] => Liu, N.
                    [6] => Shrank, W. H.
                )

            [original_url] => http://content.healthaffairs.org:80/cgi/content/short/28/1/w29?rss=1
            [tags] => 
        )

    [rdf] => Array
        (
            [rdf_about] => Array
                (
                    [0] => http://content.healthaffairs.org:80/cgi/content/short/28/4/w688?rss=1
                )

            [rss_title] => Array
                (
                    [0] => Doing More With Less: A Conversation With Kerry Weems [WEB EXCLUSIVES] 
                )

            [rss_link] => Array
                (
                    [0] => http://content.healthaffairs.org:80/cgi/content/short/28/4/w688?rss=1
                )

            [rss_description] => Array
                (
                    [0] => The Centers for Medicare and Medicaid Services (CMS) is a resource-starved agency with few friends on Capitol Hill. From the perspective of its last administrator, neither Congress nor the White ...
                )

            [prism_number] => Array
                (
                    [0] => 4
                )

            [prism_volume] => Array
                (
                    [0] => 28
                )

            [prism_endingPage] => Array
                (
                    [0] => 696
                )

            [prism_startingPage] => Array
                (
                    [0] => 688
                )

            [prism_publicationDate] => Array
                (
                    [0] => 2009-07-01
                )

            [prism_section] => Array
                (
                    [0] => WEB EXCLUSIVES
                )

            [dc_creator] => Array
                (
                    [0] => Iglehart, J. K.
                    [1] => Huskamp, H. A.
                    [2] => Zuvekas, S. H.
                    [3] => Barnato, A. E.
                    [4] => Bynum, J. P.W.
                    [5] => Gottlieb, D. J.
                    [6] => Fisher, E. S.
                    [7] => Skinner, J. S.
                )

            [dc_date] => Array
                (
                    [0] => 2009-07-01
                )

            [dc_identifier] => Array
                (
                    [0] => doi:10.1377/hlthaff.28.4.w688
                )

            [dc_title] => Array
                (
                    [0] => Doing More With Less: A Conversation With Kerry Weems
                )

            [dc_publisher] => Array
                (
                    [0] => Health Affairs
                )

        )

)