-// $Id: CQLNode.java,v 1.10 2002-11-05 17:21:30 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.
- * ##
*
- * @version $Id: CQLNode.java,v 1.10 2002-11-05 17:21:30 mike Exp $
+ * @version $Id: CQLNode.java,v 1.11 2002-11-06 00:05:58 mike Exp $
*/
public abstract class CQLNode {
+ 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();
- // Utility-function abbreviations for the use of subclasses
+ /**
+ * 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); }
- protected static String xq(String str) { return Utils.xq(str); }
- // Test harness
- public static void main (String[] args) {
- CQLNode n1 = new CQLTermNode("dc.author",
- new CQLRelation("="),
- "kernighan");
- CQLNode n2 = new CQLTermNode("dc.title",
- new CQLRelation("all"),
- "elements style");
- CQLNode root = new CQLAndNode(n1, n2);
- System.out.println(root.toXCQL(0));
- }
+ /**
+ * 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); }
}