diff --git a/src/ast/seq_decl_plugin.cpp b/src/ast/seq_decl_plugin.cpp
index f1158dd53..81783c85c 100644
--- a/src/ast/seq_decl_plugin.cpp
+++ b/src/ast/seq_decl_plugin.cpp
@@ -913,6 +913,11 @@ app* seq_decl_plugin::mk_string(zstring const& s) {
 }
 
 
+bool seq_decl_plugin::is_considered_uninterpreted(func_decl * f) {
+    seq_util util(*m_manager);
+    return util.str.is_nth_u(f);
+}
+
 bool seq_decl_plugin::is_value(app* e) const {
     while (true) {
         if (is_app_of(e, m_family_id, OP_SEQ_EMPTY)) {
diff --git a/src/ast/seq_decl_plugin.h b/src/ast/seq_decl_plugin.h
index 874262624..1f68d85dd 100644
--- a/src/ast/seq_decl_plugin.h
+++ b/src/ast/seq_decl_plugin.h
@@ -207,6 +207,7 @@ public:
 
     bool has_re() const { return m_has_re; }
 
+    bool is_considered_uninterpreted(func_decl * f) override;
 };
 
 class seq_util {
diff --git a/src/model/model.cpp b/src/model/model.cpp
index c05d9a1f3..1c678d88e 100644
--- a/src/model/model.cpp
+++ b/src/model/model.cpp
@@ -29,6 +29,12 @@ Revision History:
 #include "model/model.h"
 #include "model/model_params.hpp"
 #include "model/model_evaluator.h"
+#include "model/array_factory.h"
+#include "model/value_factory.h"
+#include "model/seq_factory.h"
+#include "model/datatype_factory.h"
+#include "model/numeral_factory.h"
+
 
 model::model(ast_manager & m):
     model_core(m),
@@ -88,40 +94,38 @@ bool model::eval_expr(expr * e, expr_ref & result, bool model_completion) {
     }
 }
 
-struct model::value_proc : public some_value_proc {
-    model & m_model;
-    value_proc(model & m):m_model(m) {}
-    expr * operator()(sort * s) override {
-        ptr_vector<expr> * u = nullptr;
-        if (m_model.m_usort2universe.find(s, u)) {
-            if (!u->empty())
-                return u->get(0);
-        }
-        return nullptr;
-    }    
-};
+value_factory* model::get_factory(sort* s) {
+    if (m_factories.plugins().empty()) {
+        seq_util su(m);
+        m_factories.register_plugin(alloc(array_factory, m, *this));
+        m_factories.register_plugin(alloc(datatype_factory, m, *this));
+        m_factories.register_plugin(alloc(bv_factory, m));
+        m_factories.register_plugin(alloc(arith_factory, m));
+        m_factories.register_plugin(alloc(seq_factory, m, su.get_family_id(), *this));
+    }
+    family_id fid = s->get_family_id();
+    return m_factories.get_plugin(fid);
+}
 
 expr * model::get_some_value(sort * s) {
-    value_proc p(*this);
-    return m.get_some_value(s, &p);
+    ptr_vector<expr> * u = nullptr;
+    if (m_usort2universe.find(s, u)) {
+        if (!u->empty())
+            return u->get(0);
+    }    
+    return m.get_some_value(s);
 }
 
 expr * model::get_fresh_value(sort * s) {
-    value_proc p(*this);
-    return m.get_some_value(s, &p);
+    return get_factory(s)->get_fresh_value(s);
 }
 
 bool model::get_some_values(sort * s, expr_ref& v1, expr_ref& v2) {
-    v1 = get_some_value(s);
-    v2 = get_some_value(s);
-    return true;
+    return get_factory(s)->get_some_values(s, v1, v2);
 }
 
 ptr_vector<expr> const & model::get_universe(sort * s) const {
-    ptr_vector<expr> * u = nullptr;
-    m_usort2universe.find(s, u);
-    SASSERT(u != nullptr);
-    return *u;
+    return *m_usort2universe[s];
 }
 
 bool model::has_uninterpreted_sort(sort * s) const {
diff --git a/src/model/model.h b/src/model/model.h
index 13c4f14b3..efe486bbb 100644
--- a/src/model/model.h
+++ b/src/model/model.h
@@ -19,10 +19,13 @@ Revision History:
 #ifndef MODEL_H_
 #define MODEL_H_
 
+#include "util/ref.h"
+#include "util/vector.h"
+#include "ast/ast_translation.h"
+#include "util/plugin_manager.h"
 #include "model/model_core.h"
 #include "model/model_evaluator.h"
-#include "util/ref.h"
-#include "ast/ast_translation.h"
+#include "model/value_factory.h"
 
 class model;
 typedef ref<model> model_ref;
@@ -37,7 +40,7 @@ protected:
     model_evaluator               m_mev;
     bool                          m_cleaned;
     bool                          m_inline;
-    struct value_proc;
+    plugin_manager<value_factory> m_factories;
 
     struct deps_collector;    
     struct occs_collector;    
@@ -52,6 +55,7 @@ protected:
     expr_ref cleanup_expr(top_sort& ts, expr* e, unsigned current_partition);
     void remove_decls(ptr_vector<func_decl> & decls, func_decl_set const & s);
     bool can_inline_def(top_sort& ts, func_decl* f);
+    value_factory* get_factory(sort* s);
 
 public:
     model(ast_manager & m);
diff --git a/src/model/seq_factory.h b/src/model/seq_factory.h
new file mode 100644
index 000000000..1ddae7d87
--- /dev/null
+++ b/src/model/seq_factory.h
@@ -0,0 +1,149 @@
+/*++
+Copyright (c) 2011 Microsoft Corporation
+
+Module Name:
+
+    theory_seq_empty.h
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2011-14-11
+
+Revision History:
+
+--*/
+#ifndef SEQ_FACTORY_H_
+#define SEQ_FACTORY_H_
+
+#include "ast/seq_decl_plugin.h"
+#include "model/model_core.h"
+
+class seq_factory : public value_factory {
+    typedef hashtable<symbol, symbol_hash_proc, symbol_eq_proc> symbol_set;
+    model_core& m_model;
+    ast_manager& m;
+    seq_util     u;
+    symbol_set   m_strings;
+    unsigned     m_next;
+    std::string  m_unique_delim;
+    obj_map<sort, expr*> m_unique_sequences;
+    expr_ref_vector m_trail;
+public:
+    
+    seq_factory(ast_manager & m, family_id fid, model_core& md):
+        value_factory(m, fid),
+        m_model(md),
+        m(m),
+        u(m),
+        m_next(0),
+        m_unique_delim("!"),
+        m_trail(m)
+    {
+        m_strings.insert(symbol(""));
+        m_strings.insert(symbol("a"));
+        m_strings.insert(symbol("b"));
+    }
+    
+    void add_trail(expr* e) {
+        m_trail.push_back(e);
+    }
+    
+    void set_prefix(char const* p) {
+        m_unique_delim = p;
+    }
+    
+    // generic method for setting unique sequences
+    void set_prefix(expr* uniq) {
+        m_trail.push_back(uniq);
+        m_unique_sequences.insert(m.get_sort(uniq), uniq);
+    }
+    
+    expr* get_some_value(sort* s) override {
+        if (u.is_seq(s)) {
+            return u.str.mk_empty(s);
+        }
+        sort* seq = nullptr;
+        if (u.is_re(s, seq)) {
+            return u.re.mk_to_re(u.str.mk_empty(seq));
+        }
+        UNREACHABLE();
+        return nullptr;
+    }
+    bool get_some_values(sort* s, expr_ref& v1, expr_ref& v2) override {
+        if (u.is_string(s)) {
+            v1 = u.str.mk_string(symbol("a"));
+            v2 = u.str.mk_string(symbol("b"));
+            return true;
+        }
+        sort* ch;
+        if (u.is_seq(s, ch)) {
+            if (m_model.get_some_values(ch, v1, v2)) {
+                v1 = u.str.mk_unit(v1);
+                v2 = u.str.mk_unit(v2);
+                return true;
+            }
+            else {
+                    return false;
+            }
+        }
+        NOT_IMPLEMENTED_YET();
+        return false; 
+    }
+    expr* get_fresh_value(sort* s) override {
+        if (u.is_string(s)) {
+            while (true) {
+                std::ostringstream strm;
+                strm << m_unique_delim << std::hex << m_next++ << std::dec << m_unique_delim;
+                symbol sym(strm.str().c_str());
+                if (m_strings.contains(sym)) continue;
+                m_strings.insert(sym);
+                return u.str.mk_string(sym);
+            }
+        }
+        sort* seq = nullptr, *ch = nullptr;
+        if (u.is_re(s, seq)) {
+            expr* v0 = get_fresh_value(seq);
+                return u.re.mk_to_re(v0);
+        }
+        if (u.is_char(s)) {
+            //char s[2] = { ++m_char, 0 };
+            //return u.str.mk_char(zstring(s), 0);
+            return u.str.mk_char(zstring("a"), 0);
+        }
+        if (u.is_seq(s, ch)) {
+            expr* v = m_model.get_fresh_value(ch);
+            if (!v) return nullptr;
+            return u.str.mk_unit(v);
+            }
+        UNREACHABLE();
+        return nullptr;
+    }
+    void register_value(expr* n) override {
+        symbol sym;
+        if (u.str.is_string(n, sym)) {
+            m_strings.insert(sym);
+            if (sym.str().find(m_unique_delim) != std::string::npos) {
+                add_new_delim();
+            }
+        }
+    }
+private:
+    
+    void add_new_delim() {
+        bool found = true;
+        while (found) {
+            found = false;
+            m_unique_delim += "!";
+            symbol_set::iterator it = m_strings.begin(), end = m_strings.end();
+            for (; it != end && !found; ++it) {
+                found = it->str().find(m_unique_delim) != std::string::npos;                    
+            }
+        }
+    }
+};
+
+#endif 
diff --git a/src/smt/proto_model/proto_model.h b/src/smt/proto_model/proto_model.h
index c73665715..587ddc510 100644
--- a/src/smt/proto_model/proto_model.h
+++ b/src/smt/proto_model/proto_model.h
@@ -31,7 +31,6 @@ Revision History:
 #include "model/model_core.h"
 #include "model/model_evaluator.h"
 #include "model/value_factory.h"
-#include "util/plugin_manager.h"
 #include "ast/arith_decl_plugin.h"
 #include "ast/func_decl_dependencies.h"
 #include "model/model.h"
diff --git a/src/smt/theory_seq_empty.h b/src/smt/theory_seq_empty.h
index 81f1af06f..ac4a37750 100644
--- a/src/smt/theory_seq_empty.h
+++ b/src/smt/theory_seq_empty.h
@@ -21,131 +21,9 @@ Revision History:
 
 #include "smt/smt_theory.h"
 #include "ast/seq_decl_plugin.h"
+#include "model/seq_factory.h"
 
 namespace smt {
-    class seq_factory : public value_factory {
-        typedef hashtable<symbol, symbol_hash_proc, symbol_eq_proc> symbol_set;
-        proto_model& m_model;
-        ast_manager& m;
-        seq_util     u;
-        symbol_set   m_strings;
-        unsigned     m_next;
-        std::string  m_unique_delim;
-        obj_map<sort, expr*> m_unique_sequences;
-        expr_ref_vector m_trail;
-    public:
-
-        seq_factory(ast_manager & m, family_id fid, proto_model& md):
-            value_factory(m, fid),
-            m_model(md),
-            m(m),
-            u(m),
-            m_next(0),
-            m_unique_delim("!"),
-            m_trail(m)
-        {
-            m_strings.insert(symbol(""));
-            m_strings.insert(symbol("a"));
-            m_strings.insert(symbol("b"));
-        }
-
-        void add_trail(expr* e) {
-            m_trail.push_back(e);
-        }
-
-        void set_prefix(char const* p) {
-            m_unique_delim = p;
-        }
-
-        // generic method for setting unique sequences
-        void set_prefix(expr* uniq) {
-            m_trail.push_back(uniq);
-            m_unique_sequences.insert(m.get_sort(uniq), uniq);
-        }
-
-        expr* get_some_value(sort* s) override {
-            if (u.is_seq(s)) {
-                return u.str.mk_empty(s);
-            }
-            sort* seq = nullptr;
-            if (u.is_re(s, seq)) {
-                return u.re.mk_to_re(u.str.mk_empty(seq));
-            }
-            UNREACHABLE();
-            return nullptr;
-        }
-        bool get_some_values(sort* s, expr_ref& v1, expr_ref& v2) override {
-            if (u.is_string(s)) {
-                v1 = u.str.mk_string(symbol("a"));
-                v2 = u.str.mk_string(symbol("b"));
-                return true;
-            }
-            sort* ch;
-            if (u.is_seq(s, ch)) {
-                if (m_model.get_some_values(ch, v1, v2)) {
-                    v1 = u.str.mk_unit(v1);
-                    v2 = u.str.mk_unit(v2);
-                    return true;
-                }
-                else {
-                    return false;
-                }
-            }
-            NOT_IMPLEMENTED_YET();
-            return false; 
-        }
-        expr* get_fresh_value(sort* s) override {
-            if (u.is_string(s)) {
-                while (true) {
-                    std::ostringstream strm;
-                    strm << m_unique_delim << std::hex << m_next++ << std::dec << m_unique_delim;
-                    symbol sym(strm.str().c_str());
-                    if (m_strings.contains(sym)) continue;
-                    m_strings.insert(sym);
-                    return u.str.mk_string(sym);
-                }
-            }
-            sort* seq = nullptr, *ch = nullptr;
-            if (u.is_re(s, seq)) {
-                expr* v0 = get_fresh_value(seq);
-                return u.re.mk_to_re(v0);
-            }
-            if (u.is_char(s)) {
-                //char s[2] = { ++m_char, 0 };
-                //return u.str.mk_char(zstring(s), 0);
-                return u.str.mk_char(zstring("a"), 0);
-            }
-            if (u.is_seq(s, ch)) {
-                expr* v = m_model.get_fresh_value(ch);
-				if (!v) return nullptr;
-                return u.str.mk_unit(v);
-            }
-            UNREACHABLE();
-            return nullptr;
-        }
-        void register_value(expr* n) override {
-            symbol sym;
-            if (u.str.is_string(n, sym)) {
-                m_strings.insert(sym);
-                if (sym.str().find(m_unique_delim) != std::string::npos) {
-                    add_new_delim();
-                }
-            }
-        }
-    private:
-
-        void add_new_delim() {
-            bool found = true;
-            while (found) {
-                found = false;
-                m_unique_delim += "!";
-                symbol_set::iterator it = m_strings.begin(), end = m_strings.end();
-                for (; it != end && !found; ++it) {
-                    found = it->str().find(m_unique_delim) != std::string::npos;                    
-                }
-            }
-        }
-    };
 
     class theory_seq_empty : public theory {
         bool m_used;