diff --git a/src/ast/seq_decl_plugin.cpp b/src/ast/seq_decl_plugin.cpp
index 53e0966fc..40119043a 100644
--- a/src/ast/seq_decl_plugin.cpp
+++ b/src/ast/seq_decl_plugin.cpp
@@ -1637,45 +1637,102 @@ seq_util::rex::info seq_util::rex::get_info_rec(expr* e) const {
 */
 seq_util::rex::info seq_util::rex::mk_info_rec(app* e) const {
     info i1, i2;
+    lbool nullable(l_false);
+    unsigned min_length(0), lower_bound(0);
+    bool normalized(false);
     if (e->get_family_id() == u.get_family_id()) {
         switch (e->get_decl()->get_decl_kind())
         {
         case OP_RE_EMPTY_SET:
-            return info(UINT_MAX);
+            return info(true, true, true, true, true, true, false, l_false, UINT_MAX, 0);
         case OP_RE_FULL_SEQ_SET:
+            return info(true, true, true, true, true, true, false, l_true, 0, 1);
         case OP_RE_STAR:
+            i1 = get_info_rec(e->get_arg(0));
+            return info(i1.classical, i1.classical, i1.interpreted, i1.nonbranching, i1.normalized, i1.monadic, false, l_true, 0, i1.star_height + 1);
         case OP_RE_OPTION:
-            return info(0);
+            i1 = get_info_rec(e->get_arg(0));
+            return info(i1.classical, i1.classical, i1.interpreted, i1.nonbranching, i1.normalized, i1.monadic, false, l_true, 0, i1.star_height);
         case OP_RE_RANGE:
         case OP_RE_FULL_CHAR_SET:
         case OP_RE_OF_PRED:
-            return info(1);
+            //TBD: check if the character predicate contains uninterpreted symbols or is nonground or is unsat
+            //TBD: check if the range is unsat
+            return info(true, true, true, true, true, true, true, l_false, 1, 0);
         case OP_RE_CONCAT:
             i1 = get_info_rec(e->get_arg(0));
             i2 = get_info_rec(e->get_arg(1));
-            return info(u.max_plus(i1.min_length, i2.min_length));
+            return info(i1.classical & i2.classical,
+                i1.classical && i2.classical, //both args of concat must be classical for it to be standard
+                i1.interpreted && i2.interpreted,
+                i1.nonbranching && i2.nonbranching,
+                (i1.normalized && !u.re.is_concat(e->get_arg(0)) && i2.normalized),
+                i1.monadic && i2.monadic,
+                false,
+                ((i1.nullable == l_false || i2.nullable == l_false) ? l_false : ((i1.nullable == l_true && i2.nullable == l_true) ? l_true : l_undef)),
+                u.max_plus(i1.min_length, i2.min_length),
+                std::max(i1.star_height, i2.star_height));
         case OP_RE_UNION:
             i1 = get_info_rec(e->get_arg(0));
             i2 = get_info_rec(e->get_arg(1));
-            return info(std::min(i1.min_length, i2.min_length));
+            return info(i1.classical & i2.classical,
+                i1.standard && i2.standard,
+                i1.interpreted && i2.interpreted,
+                i1.nonbranching && i2.nonbranching,
+                i1.normalized && i2.normalized,
+                i1.monadic && i2.monadic,
+                i1.singleton && i2.singleton,
+                ((i1.nullable == l_true || i2.nullable == l_true) ? l_true : ((i1.nullable == l_false && i2.nullable == l_false) ? l_false : l_undef)),
+                std::min(i1.min_length, i2.min_length),
+                std::max(i1.star_height, i2.star_height));
         case OP_RE_INTERSECT:
             i1 = get_info_rec(e->get_arg(0));
             i2 = get_info_rec(e->get_arg(1));
-            return info(std::max(i1.min_length, i2.min_length));
+            return info(false,
+                i1.standard && i2.standard,
+                i1.interpreted && i2.interpreted,
+                i1.nonbranching && i2.nonbranching,
+                i1.normalized && i2.normalized,
+                i1.monadic && i2.monadic,
+                i1.singleton && i2.singleton,
+                ((i1.nullable == l_true && i2.nullable == l_true) ? l_true : ((i1.nullable == l_false || i2.nullable == l_false) ? l_false : l_undef)),
+                std::max(i1.min_length, i2.min_length),
+                std::max(i1.star_height, i2.star_height));
         case OP_SEQ_TO_RE:
-            return info(u.str.min_length(e->get_arg(0)));
+            //TBD: the sequence is not a concrete value
+            min_length = u.str.min_length(e->get_arg(0));
+            return info(true, true, true, true, true, true, (min_length == 1 && u.str.max_length(e->get_arg(0)) == 1), l_false, min_length, 0);
         case OP_RE_REVERSE:
-        case OP_RE_PLUS:
             return get_info_rec(e->get_arg(0));
+        case OP_RE_PLUS:
+            i1 = get_info_rec(e->get_arg(0));
+            //r+ is not normalized if r is nullable, the normalized form would be r*
+            return info(i1.classical, i1.classical, i1.interpreted, i1.nonbranching, (i1.nullable == l_false ? i1.normalized : false), i1.monadic, false, l_true, 0, i1.star_height + 1);
         case OP_RE_COMPLEMENT:
-            return info(0); 
+            i1 = get_info_rec(e->get_arg(0));
+            nullable = (i1.nullable == l_true ? l_false : (i1.nullable == l_false ? l_true : l_undef));
+            min_length = (nullable == l_false ? 1 : 0);
+            return info(false, i1.standard, i1.interpreted, i1.nonbranching, i1.normalized, i1.monadic, false, nullable, min_length, i1.star_height);
         case OP_RE_LOOP:
             i1 = get_info_rec(e->get_arg(0));
-            return info(u.max_mul(i1.min_length, e->get_decl()->get_parameter(0).get_int()));
+            lower_bound = e->get_decl()->get_parameter(0).get_int();
+            //r{l,m} is not normalized if r is nullable but l > 0
+            normalized = (i1.nullable == l_false && lower_bound > 0 ? false : i1.normalized);
+            nullable = (i1.nullable == l_true || lower_bound == 0 ? l_true : i1.nullable);
+            return info(i1.classical, i1.classical, i1.interpreted, i1.nonbranching, normalized, i1.singleton, false, nullable, u.max_mul(i1.min_length, lower_bound), i1.star_height);
         case OP_RE_DIFF:
             i1 = get_info_rec(e->get_arg(0));
             i2 = get_info_rec(e->get_arg(1));
-            return info(std::max(i1.min_length, i2.min_length > 0 ? 0 : UINT_MAX));
+            return info(false,
+                i1.standard & i2.standard,
+                i1.interpreted & i2.interpreted,
+                i1.nonbranching & i2.nonbranching,
+                i1.normalized & i2.normalized,
+                i1.monadic & i2.monadic,
+                false,
+                ((i1.nullable == l_true && i2.nullable == l_false) ? l_true : ((i1.nullable == l_false || i2.nullable == l_false) ? l_false : l_undef)),
+                std::max(i1.min_length, i2.min_length),
+                std::max(i1.star_height, i2.star_height));
         }
         return invalid_info;
     }
@@ -1683,21 +1740,39 @@ seq_util::rex::info seq_util::rex::mk_info_rec(app* e) const {
     if (u.m.is_ite(e, c, t, f)) {
         i1 = get_info_rec(t);
         i2 = get_info_rec(f);
-        return info(std::min(i1.min_length, i2.min_length));
+        min_length = std::min(i1.min_length, i2.min_length);
+        nullable = (i1.nullable == i2.nullable ? i1.nullable : l_undef);
+        //TBD: whether ite is interpreted or not depends on whether the condition is interpreted and both branches are interpreted
+        return info(false, false, false, false, i1.normalized && i2.normalized, i1.monadic && i2.monadic, i1.singleton && i2.singleton, nullable, min_length, std::max(i1.star_height, i2.star_height));
     }
     return invalid_info;
 }
 
 std::ostream& seq_util::rex::info::display(std::ostream& out) const {
-    if (valid)
-        out << "info(" << "min_length=" << min_length << ")";
+    if (valid) {
+        out << "info("
+            << "nullable=" << (nullable == l_true ? "T" : (nullable == l_false ? "F" : "U")) << ", "
+            << "classical=" << (classical ? "T" : "F") << ", "
+            << "standard=" << (standard ? "T" : "F") << ", "
+            << "nonbranching=" << (nonbranching ? "T" : "F") << ", "
+            << "normalized=" << (normalized ? "T" : "F") << ", "
+            << "monadic=" << (monadic ? "T" : "F") << ", "
+            << "singleton=" << (singleton ? "T" : "F") << ", "
+            << "min_length=" << min_length << ", "
+            << "star_height=" << star_height << ")";
+    }
     else
-        out << "invalid_info";
+        out << "UNDEF";
     return out;
 }
 
+/*
+  String representation of the info.
+*/
 std::string seq_util::rex::info::str() const {
     std::ostringstream out;
     display(out);
     return out.str();
 }
+
+
diff --git a/src/ast/seq_decl_plugin.h b/src/ast/seq_decl_plugin.h
index 1110c06c5..eec2dd7af 100644
--- a/src/ast/seq_decl_plugin.h
+++ b/src/ast/seq_decl_plugin.h
@@ -25,6 +25,7 @@ Revision History:
 #include "ast/ast.h"
 #include "ast/bv_decl_plugin.h"
 #include <string>
+#include "util/lbool.h"
 
 #define Z3_USE_UNICODE 0
 
@@ -411,13 +412,62 @@ public:
     class rex {
     public:
         struct info {
+            /* Value is well-defined. */
             bool valid;
+            /* No complement, no intersection, no difference, and no if-then-else is used. Reverse is allowed. */
+            bool classical;
+            /* Boolean-reverse combination of classical regexes (using reverse, union, complement, intersection or difference). */
+            bool standard;
+            /* There are no uninterpreted symbols. */
+            bool interpreted;
+            /* No if-then-else is used. */
+            bool nonbranching;
+            /* Concatenations are right associative and if a loop body is nullable then the lower bound is zero. */
+            bool normalized;
+            /* All bounded loops have a body that is a singleton. */
+            bool monadic;
+            /* Positive Boolean combination of ranges or predicates or singleton sequences. */
+            bool singleton;
+            /* If l_true then empty word is accepted, if l_false then empty word is not accepted. */
+            lbool nullable;
+            /* Lower bound on the length of all accepted words. */
             unsigned min_length;
-            info() : valid(false), min_length(0) {}
-            info(unsigned k) : valid(true), min_length(k) {}
-            bool is_valid() { return valid; }
+            /* Maximum nesting depth of Kleene stars. */
+            unsigned star_height;
+
+            /* 
+              Constructs an invalid info
+            */
+            info() : valid(false) {}
+
+            /* 
+              General info constructor.
+            */
+            info(bool is_classical, 
+                bool is_standard, 
+                bool is_interpreted, 
+                bool is_nonbranching, 
+                bool is_normalized, 
+                bool is_monadic, 
+                bool is_singleton,
+                lbool is_nullable, 
+                unsigned min_l, 
+                unsigned star_h) :
+                valid(true), classical(is_classical), standard(is_standard), interpreted(is_interpreted), nonbranching(is_nonbranching),
+                normalized(is_normalized), monadic(is_monadic), nullable(is_nullable), singleton(is_singleton), 
+                min_length(min_l), star_height(star_h) {}
+
+            /*
+              Appends a string representation of the info into the stream.
+            */
             std::ostream& display(std::ostream&) const;
+
+            /*
+              Returns a string representation of the info.
+            */
             std::string str() const;
+
+            bool is_valid() const { return valid; }
         };
     private:
         seq_util&    u;
@@ -536,3 +586,4 @@ public:
 inline std::ostream& operator<<(std::ostream& out, seq_util::rex::pp const & p) { return p.display(out); }
 
 inline std::ostream& operator<<(std::ostream& out, seq_util::rex::info const& p) { return p.display(out); }
+
diff --git a/src/smt/seq_regex.cpp b/src/smt/seq_regex.cpp
index ff1f57abd..4852347bc 100644
--- a/src/smt/seq_regex.cpp
+++ b/src/smt/seq_regex.cpp
@@ -793,11 +793,12 @@ namespace smt {
         }
         STRACE("seq_regex", tout << "Updating state graph for regex "
                                  << mk_pp(r, m) << ") ";);
-        if (!m_state_graph.is_seen(r_id))
-            STRACE("state_graph", tout << std::endl << "state(" << r_id << ") = " << seq_util::rex::pp(re(), r) << std::endl;);
+        
+        STRACE("state_graph",
+            if (!m_state_graph.is_seen(r_id))
+                tout << std::endl << "state(" << r_id << ") = " << seq_util::rex::pp(re(), r) << std::endl << "info(" << r_id << ") = " << re().get_info(r) << std::endl;);
         // Add state
         m_state_graph.add_state(r_id);
-        STRACE("state_graph", tout << "regex(" << r_id << ") = " << mk_pp(r, m) << std::endl;);
         STRACE("seq_regex", tout << "Updating state graph for regex "
                                  << mk_pp(r, m) << ") " << std::endl;);
         STRACE("seq_regex_brief", tout << std::endl << "USG("
@@ -815,12 +816,12 @@ namespace smt {
             for (auto const& dr: derivatives) {
                 unsigned dr_id = get_state_id(dr);
                 STRACE("seq_regex_verbose", tout
-                    << std::endl << "  traversing deriv: " << dr_id << " ";);
-                if (!m_state_graph.is_seen(dr_id))
-                    STRACE("state_graph", tout << "state(" << dr_id << ") = " << seq_util::rex::pp(re(), dr) << std::endl;);
+                    << std::endl << "  traversing deriv: " << dr_id << " ";);              
+                STRACE("state_graph",
+                    if (!m_state_graph.is_seen(dr_id))
+                        tout << "state(" << dr_id << ") = " << seq_util::rex::pp(re(), dr) << std::endl << "info(" << dr_id << ") = " << re().get_info(dr) << std::endl;);
                 // Add state
                 m_state_graph.add_state(dr_id);
-                STRACE("state_graph", tout << "regex(" << dr_id << ") = " << mk_pp(dr, m) << std::endl;);
                 bool maybecycle = can_be_in_cycle(r, dr);
                 m_state_graph.add_edge(r_id, dr_id, maybecycle);
             }