re-organize muz_qe into separate units

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/muz/rel/dl_mk_simple_joins.h

@@ -0,0 +1,63 @@
+/*++
+Copyright (c) 2006 Microsoft Corporation
+
+Module Name:
+
+    dl_mk_simple_joins.h
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Leonardo de Moura (leonardo) 2010-05-20.
+
+Revision History:
+
+--*/
+#ifndef _DL_MK_SIMPLE_JOINS_H_
+#define _DL_MK_SIMPLE_JOINS_H_
+
+#include"map.h"
+#include"obj_pair_hashtable.h"
+
+#include"dl_context.h"
+#include"dl_rule_set.h"
+#include"dl_rule_transformer.h"
+
+namespace datalog {
+
+    /**
+       \brief Functor for creating rules that contain simple joins.
+       A simple join is the join of two tables.
+
+       After applying this transformation, every rule has at most one join.
+       So, the rules will have the form
+
+          HEAD :- TAIL.
+          HEAD :- TAIL_1, TAIL_2.
+         
+       We also assume a rule may contain interpreted expressions that work as filtering conditions.
+       So, we may also have:
+
+          HEAD :- TAIL, C_1, ..., C_n.
+          HEAD :- TAIL_1, TAIL_2, C_1, ..., C_n.
+          
+       Where the C_i's are interpreted expressions.
+
+       We say that a rule containing C_i's is a rule with a "big tail".
+    */
+    class mk_simple_joins : public rule_transformer::plugin {
+        context & 	    m_context;
+        rule_manager &      rm;
+    public:
+        mk_simple_joins(context & ctx);
+        
+        rule_set * operator()(rule_set const & source);
+    };
+
+};
+
+#endif /* _DL_MK_SIMPLE_JOINS_H_ */
+