01: /*
02: * Copyright (c) 2002-2003 by OpenSymphony
03: * All rights reserved.
04: */
05: package com.opensymphony.workflow.query;
06:
07: import java.io.Serializable;
08:
09: /**
10: * Abstract base class for expressions used in a workflow query.
11: * Expressions can be negate and/or nested. The default is not negate.
12: * <p></p>
13: * Expressions which are supported by all stores are {@link FieldExpression} and {@link NestedExpression}.
14: * <p></p>
15: * Store specific expressions like XPathExpression can be added.
16: *
17: * @author Christine Zimmermann
18: */
19: public abstract class Expression implements Serializable {
20: //~ Instance fields ////////////////////////////////////////////////////////
21:
22: protected boolean negate = false;
23:
24: //~ Constructors ///////////////////////////////////////////////////////////
25:
26: protected Expression() {
27: }
28:
29: //~ Methods ////////////////////////////////////////////////////////////////
30:
31: public boolean isNegate() {
32: return negate;
33: }
34:
35: abstract public boolean isNested();
36: }
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