1 // $Id: CQLNode.java,v 1.14 2002-11-17 23:29:02 mike Exp $
3 package org.z3950.zing.cql;
4 import java.util.Properties;
8 * Represents a node in a CQL parse-tree.
10 * @version $Id: CQLNode.java,v 1.14 2002-11-17 23:29:02 mike Exp $
12 public abstract class CQLNode {
13 CQLNode() {} // prevent javadoc from documenting this
16 * Translates a parse-tree into an XCQL document.
19 * The number of levels to indent the top element of the XCQL
20 * document. This will typically be 0 when invoked by an
21 * application; it takes higher values when this method is
22 * invoked recursively for nodes further down the tree.
24 * A String containing an XCQL document equivalent to the
25 * parse-tree whose root is this node.
27 abstract public String toXCQL(int level);
30 * Decompiles a parse-tree into a CQL query.
33 * A String containing a CQL query equivalent to the parse-tree
34 * whose root is this node, so that compiling that query will
35 * yield an identical tree.
37 abstract public String toCQL();
40 * Renders a parse-tree into a Yaz-style PQF string.
41 * PQF, or Prefix Query Format, is a cryptic but powerful notation
42 * that can be trivially mapped, one-to-one, int Z39.50 Type-1 and
43 * Type-101 queries. A specification for the format can be found
45 * <A href="http://indexdata.dk/yaz/doc/tools.php#PQF"
46 * >Chapter 7 (Supporting Tools)</A> of the
47 * <A href="http://indexdata.dk/yaz/">YAZ</A> manual.
50 * A <TT>Properties</TT> object containing configuration
51 * information that specifies the mapping from CQL qualifiers,
52 * relations, etc. to Type-1 attributes. The mapping
53 * specification is described in the cql-java distribution's
54 * sample PQF-mapping configuration file,
55 * <TT>etc/pqf.properties</TT>, which see.
57 * A String containing a PQF query equivalent to the parse-tree
58 * whose root is this node. This may be fed into the tool of
59 * your choice to obtain a BER-encoded packet.
61 abstract public String toPQF(Properties config)
62 throws PQFTranslationException;
65 * Returns a String of spaces for indenting to the specified level.
67 protected static String indent(int level) { return Utils.indent(level); }
70 * Returns the argument String quoted for XML.
71 * For example, each occurrence of <TT><</TT> is translated to
74 protected static String xq(String str) { return Utils.xq(str); }