-// $Id: CQLNode.java,v 1.3 2002-10-25 16:04:44 mike Exp $
+// $Id: CQLNode.java,v 1.11 2002-11-06 00:05:58 mike Exp $
package org.z3950.zing.cql;
+import java.util.Properties;
/**
- * Represents a node in a CQL parse-tree ...
- * ###
+ * Represents a node in a CQL parse-tree.
*
- * @version $Id: CQLNode.java,v 1.3 2002-10-25 16:04:44 mike Exp $
+ * @version $Id: CQLNode.java,v 1.11 2002-11-06 00:05:58 mike Exp $
*/
public abstract class CQLNode {
- abstract String toXCQL(int level);
- abstract String toCQL();
-
- protected String indent(int level) {
- String x = "";
- while (level-- > 0) {
- x += " ";
- }
- return x;
- }
-
- // Test harness
- public static void main (String[] args) {
- CQLNode n1 = new CQLTermNode("dc.author", "=", "kernighan");
- CQLNode n2 = new CQLTermNode("dc.title", "all", "elements style");
- CQLNode root = new CQLAndNode(n1, n2);
- System.out.println(root.toXCQL(3));
- }
+ CQLNode() {} // prevent javadoc from documenting this
+
+ /**
+ * Translates a parse-tree into an XCQL document.
+ * <P>
+ * @param level
+ * The number of levels to indent the top element of the XCQL
+ * document. This will typically be 0 when invoked by an
+ * application; it takes higher values when this method is
+ * invoked recursively for nodes further down the tree.
+ * @return
+ * A String containing an XCQL document equivalent to the
+ * parse-tree whose root is this node.
+ */
+ abstract public String toXCQL(int level);
+
+ /**
+ * 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.
+ * <P>
+ * @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 UnknownQualifierException, UnknownRelationException;
+
+ /**
+ * 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); }
}