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John Caron writes: # I am still unclear: if the internal DTD declares an element, what happens if # the external DTD does also? The validator will complain that the element was declared more than once. # If the second declaration gets ignored Not ignored--carefully scrutinized and upbraided for its impertinence. # Are you referring to this line in the Capabilities DTD? It seems very # similar to what Joe was trying to do. Were you trying to make a standard # list that could be extended? The XML you cite is from the older WMS version 1.0--see <http://www.digitalearth.gov/wmt/xml/> for DTD and sample XML. # <!-- This WMT-wide list of possible output formats can be redefined by # individual servers; see the sample XML. --> # <!ENTITY % KnownFormats " GIF | JPEG | PNG | WebCGM | SVG | GML.1 | GML.2 | # GML.3 | WBMP | WMS_XML | MIME | INIMAGE | TIFF | GeoTIFF | PPM | BLANK " > Seeing this reminds me that you *can* redefine an ENTITY (but not an ELEMENT) using the internal DTD. This may suit your needs. WMS 1.1.x no longer uses this mechanism (because element names like <GIF/> were replaced by MIME type text values like <Format>image/gif</Format>). -Jeff DLB