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diff --git a/forms/source/xforms/computedexpression.hxx b/forms/source/xforms/computedexpression.hxx
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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#pragma once
+
+#include <rtl/ustring.hxx>
+#include <com/sun/star/uno/Reference.hxx>
+
+// forward declaractions
+namespace com::sun::star
+{
+    namespace xml
+    {
+        namespace dom { class XNode; }
+        namespace dom { class XNodeset; }
+        namespace xpath { class XXPathAPI; }
+        namespace xpath { class XXPathObject; }
+    }
+    namespace container { class XNameContainer; }
+}
+namespace xforms { class EvaluationContext; }
+
+
+namespace xforms
+{
+
+/** ComputedExpression represents an XPath Expression and caches results.
+ *
+ * As this class has no virtual methods, it should never be used
+ * polymorphically. */
+class ComputedExpression
+{
+    /// the expression string
+    OUString msExpression;
+
+    /// is msExpression empty?
+    bool mbIsEmpty;
+
+protected:
+    /// is msExpression a simple expression?
+    bool mbIsSimple;
+
+    /// the result from the last bind
+    css::uno::Reference<css::xml::xpath::XXPathObject> mxResult;
+
+
+    /// implementation of isSimpleExpression
+    bool _checkExpression( const char* pExpression ) const;
+
+    /// allow manipulation of the expression before it is evaluated
+    // the default implementation is to do nothing...
+    const OUString& _getExpressionForEvaluation() const { return msExpression; }
+
+    /// obtain a (suitable) XPathAPI implementation
+    static css::uno::Reference<css::xml::xpath::XXPathAPI> _getXPathAPI(const xforms::EvaluationContext& aContext);
+
+    /// evaluate the expression relative to the content node.
+    bool _evaluate( const xforms::EvaluationContext& rContext,
+                    const OUString& sExpression );
+
+
+public:
+    ComputedExpression();
+    ~ComputedExpression();
+
+
+    /// get the expression string
+    const OUString& getExpression() const { return msExpression;}
+
+    /// set a new expression string
+    void setExpression( const OUString& rExpression );
+
+    /// do we have an actual expression?
+    bool isEmptyExpression() const { return mbIsEmpty;}
+
+    /// heuristically determine whether this expression is 'simple',
+    /// i.e. whether its value will change depending on the values
+    /// of other nodes
+    bool isSimpleExpression() const;
+
+
+    /// evaluate the expression relative to the content node.
+    bool evaluate( const xforms::EvaluationContext& rContext );
+
+
+    /// does this expression have a value?
+    bool hasValue() const;
+
+
+    /// remove value/evaluate results
+    void clear();
+
+
+    // get the result of this expression as string/bool/...
+    // (Results will be based on the last call of evaluate(..). The caller
+    // must call evaluate to ensure current results.)
+    css::uno::Reference<css::xml::xpath::XXPathObject> const & getXPath() const { return mxResult;}
+    bool getBool( bool bDefault = false ) const;
+    OUString getString() const;
+
+};
+
+} // namespace xforms
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */