private boolean isValidURL(String value) {
        try {
            URL.parse(value);
            return true;
        } catch (GalimatiasParseException e) {
        }

        if (value.startsWith("/") || value.startsWith("./")
                || value.startsWith("../")) {
            try {
                URL.parse("https://example.com/" + value);
                return true;
            } catch (GalimatiasParseException e) {
            }
        }

        return false;
    }
@see nu.validator.checker.Checker#endElement(java.lang.String,
     java.lang.String, java.lang.String)
src/nu/validator/checker/schematronequiv/Assertions.java