+
+ /**
+ * Decompiles a parse-tree into a CQL query.
+ * <P>
+ * @return
+ * A String containing a CQL query equivalent to the parse-tree
+ * whose root is this node, so that compiling that query will
+ * yield an identical tree.
+ */
+ abstract public String toCQL();
+
+ /**
+ * Renders a parse-tree into a Yaz-style PQF string.
+ * PQF, or Prefix Query Format, is a cryptic but powerful notation
+ * that can be trivially mapped, one-to-one, int Z39.50 Type-1 and
+ * Type-101 queries. A specification for the format can be found
+ * in
+ * <A href="http://indexdata.dk/yaz/doc/tools.php#PQF"
+ * >Chapter 7 (Supporting Tools)</A> of the
+ * <A href="http://indexdata.dk/yaz/">YAZ</A> manual.
+ * <P>
+ * @param config
+ * A <TT>Properties</TT> object containing configuration
+ * information that specifies the mapping from CQL qualifiers,
+ * relations, etc. to Type-1 attributes. The mapping
+ * specification is described in the cql-java distribution's
+ * sample PQF-mapping configuration file,
+ * <TT>etc/pqf.properties</TT>, which see.
+ * @return
+ * A String containing a PQF query equivalent to the parse-tree
+ * whose root is this node. This may be fed into the tool of
+ * your choice to obtain a BER-encoded packet.
+ */
+ abstract public String toPQF(Properties config)
+ throws PQFTranslationException;
+
+ /**
+ * Returns a String of spaces for indenting to the specified level.
+ */
+ protected static String indent(int level) { return Utils.indent(level); }
+
+ /**
+ * Returns the argument String quoted for XML.
+ * For example, each occurrence of <TT><</TT> is translated to
+ * <TT>&lt;</TT>.
+ */
+ protected static String xq(String str) { return Utils.xq(str); }