diff --git a/stix2/__init__.py b/stix2/__init__.py
index a1eaa56..637672a 100644
--- a/stix2/__init__.py
+++ b/stix2/__init__.py
@@ -4,8 +4,9 @@
 
 from . import exceptions
 from .bundle import Bundle
-from .constants import (FloatConstant, HashConstant, IntegerConstant,
-                        StringConstant)
+from .constants import (FloatConstant, HashConstant, HexConstant,
+                        IntegerConstant, StringConstant)
+from .object_path import ObjectPath, ObjectPathComponent
 from .observables import (URL, AlternateDataStream, ArchiveExt, Artifact,
                           AutonomousSystem, CustomObservable, Directory,
                           DomainName, EmailAddress, EmailMessage,
@@ -29,6 +30,8 @@ from .pattern_expressions import (AndBooleanExpression,
                                   FollowedByObservableExpression,
                                   GreaterThanComparisonExpression,
                                   GreaterThanEqualComparisonExpression,
+                                  IsSubsetComparisonExpression,
+                                  IsSupersetComparisonExpression,
                                   LessThanComparisonExpression,
                                   LessThanEqualComparisonExpression,
                                   LikeComparisonExpression,
diff --git a/stix2/constants.py b/stix2/constants.py
index fb84c19..142e9d7 100644
--- a/stix2/constants.py
+++ b/stix2/constants.py
@@ -121,5 +121,15 @@ class ListConstant(Constant):
 
 
 def make_constant(value):
-    # TODO: Stub
-    pass
+    if isinstance(value, str):
+        return StringConstant(value)
+    elif isinstance(value, int):
+        return IntegerConstant(value)
+    elif isinstance(value, float):
+        return FloatConstant(value)
+    elif isinstance(value, list):
+        return ListConstant(value)
+    elif isinstance(value, bool):
+        return BooleanConstant(value)
+    else:
+        raise ValueError("Unable to create a constant from %s" % value)
diff --git a/stix2/object_path.py b/stix2/object_path.py
new file mode 100644
index 0000000..22ebef7
--- /dev/null
+++ b/stix2/object_path.py
@@ -0,0 +1,59 @@
+
+class ObjectPathComponent(object):
+    pass
+
+
+class BasicObjectPathComponent(ObjectPathComponent):
+    def __init__(self, property_name, is_key=False):
+        self.property_name = property_name
+        # TODO: set is_key to True if this component is a dictionary key
+        # self.is_key = is_key
+
+    def __str__(self):
+        return self.property_name
+
+
+class ListObjectPathComponent(ObjectPathComponent):
+    def __init__(self, property_name, index):
+        self.property_name = property_name
+        self.index = index
+
+    def __str__(self):
+        return "%s[%s]" % (self.property_name, self.index)
+
+
+class ReferenceObjectPathComponent(ObjectPathComponent):
+    def __init__(self, reference_property_name):
+        self.property_name = reference_property_name
+
+    def __str__(self):
+        return self.property_name
+
+
+class ObjectPath(object):
+    def __init__(self, object_type_name, property_path):
+        self.object_type_name = object_type_name
+        self.property_path = [x if isinstance(x, ObjectPathComponent) else ObjectPath.create_ObjectPathComponent(x)
+                              for x in property_path]
+
+    def __str__(self):
+        return "%s:%s" % (self.object_type_name, ".".join(["%s" % x for x in self.property_path]))
+
+    def merge(self, other):
+        self.property_path.extend(other.property_path)
+        return self
+
+    @staticmethod
+    def make_object_path(lhs):
+        path_as_parts = lhs.split(":")
+        return ObjectPath(path_as_parts[0], path_as_parts[1].split("."))
+
+    @staticmethod
+    def create_ObjectPathComponent(component_name):
+        if component_name.endswith("_ref"):
+            return ReferenceObjectPathComponent(component_name)
+        elif component_name.find("[") != -1:
+            parse1 = component_name.split("[")
+            return ListObjectPathComponent(parse1[0], parse1[1][:-1])
+        else:
+            return BasicObjectPathComponent(component_name)
diff --git a/stix2/observables.py b/stix2/observables.py
index e38e298..366e007 100644
--- a/stix2/observables.py
+++ b/stix2/observables.py
@@ -123,7 +123,7 @@ class DomainName(_Observable):
 
 
 class EmailAddress(_Observable):
-    _type = 'email-address'
+    _type = 'email-addr'
     _properties = {
         'type': TypeProperty(_type),
         'value': StringProperty(required=True),
@@ -651,7 +651,7 @@ OBJ_MAP_OBSERVABLE = {
     'autonomous-system': AutonomousSystem,
     'directory': Directory,
     'domain-name': DomainName,
-    'email-address': EmailAddress,
+    'email-addr': EmailAddress,
     'email-message': EmailMessage,
     'file': File,
     'ipv4-addr': IPv4Address,
diff --git a/stix2/pattern_expressions.py b/stix2/pattern_expressions.py
index 12aadc2..6804389 100644
--- a/stix2/pattern_expressions.py
+++ b/stix2/pattern_expressions.py
@@ -1,13 +1,9 @@
-from .constants import ListConstant, make_constant
+from .constants import Constant, IntegerConstant, ListConstant, make_constant
+from .object_path import ObjectPath
 
 
 class PatternExpression(object):
 
-    @staticmethod
-    def get_root_from_object_path(lhs):
-        path_as_parts = lhs.split(":")
-        return path_as_parts[0]
-
     @staticmethod
     def escape_quotes_and_backslashes(s):
         return s.replace(u'\\', u'\\\\').replace(u"'", u"\\'")
@@ -19,13 +15,16 @@ class ComparisonExpression(PatternExpression):
             self.operator = "IN"
         else:
             self.operator = operator
-        self.lhs = lhs
-        if isinstance(rhs, str):
-            self.rhs = make_constant(rhs)
+        if isinstance(lhs, ObjectPath):
+            self.lhs = lhs
         else:
+            self.lhs = ObjectPath.make_object_path(lhs)
+        if isinstance(rhs, Constant):
             self.rhs = rhs
+        else:
+            self.rhs = make_constant(rhs)
         self.negated = negated
-        self.root_type = self.get_root_from_object_path(lhs)
+        self.root_type = self.lhs.object_type_name
 
     def __str__(self):
         # if isinstance(self.rhs, list):
@@ -81,7 +80,14 @@ class MatchesComparisonExpression(ComparisonExpression):
         super(MatchesComparisonExpression, self).__init__("MATCHES", lhs, rhs, negated)
 
 
-# TODO: ISASUBSET, ISSUPERSET
+class IsSubsetComparisonExpression(ComparisonExpression):
+        def __init__(self, lhs, rhs, negated=False):
+            super(IsSubsetComparisonExpression, self).__init__("ISSUBSET", lhs, rhs, negated)
+
+
+class IsSupersetComparisonExpression(ComparisonExpression):
+        def __init__(self, lhs, rhs, negated=False):
+            super(IsSupersetComparisonExpression, self).__init__("ISSUPERSET", lhs, rhs, negated)
 
 
 class BooleanExpression(PatternExpression):
@@ -165,7 +171,12 @@ class ExpressionQualifier(PatternExpression):
 
 class RepeatQualifier(ExpressionQualifier):
     def __init__(self, times_to_repeat):
-        self.times_to_repeat = times_to_repeat
+        if isinstance(times_to_repeat, IntegerConstant):
+            self.times_to_repeat = times_to_repeat
+        elif isinstance(times_to_repeat, int):
+            self.times_to_repeat = IntegerConstant(times_to_repeat)
+        else:
+            raise ValueError("%s is not a valid argument for a Within Qualifier" % times_to_repeat)
 
     def __str__(self):
         return "REPEATS %s TIMES" % self.times_to_repeat
@@ -173,7 +184,12 @@ class RepeatQualifier(ExpressionQualifier):
 
 class WithinQualifier(ExpressionQualifier):
     def __init__(self, number_of_seconds):
-        self.number_of_seconds = number_of_seconds
+        if isinstance(number_of_seconds, IntegerConstant):
+            self.number_of_seconds = number_of_seconds
+        elif isinstance(number_of_seconds, int):
+            self.number_of_seconds = IntegerConstant(number_of_seconds)
+        else:
+            raise ValueError("%s is not a valid argument for a Within Qualifier" % number_of_seconds)
 
     def __str__(self):
         return "WITHIN %s SECONDS" % self.number_of_seconds
@@ -181,8 +197,18 @@ class WithinQualifier(ExpressionQualifier):
 
 class StartStopQualifier(ExpressionQualifier):
     def __init__(self, start_time, stop_time):
-        self.start_time = start_time
-        self.stop_time = stop_time
+        if isinstance(start_time, IntegerConstant):
+            self.start_time = start_time
+        elif isinstance(start_time, int):
+            self.start_time = IntegerConstant(start_time)
+        else:
+            raise ValueError("%s is not a valid argument for a Within Qualifier" % start_time)
+        if isinstance(stop_time, IntegerConstant):
+            self.stop_time = stop_time
+        elif isinstance(stop_time, int):
+            self.stop_time = IntegerConstant(stop_time)
+        else:
+            raise ValueError("%s is not a valid argument for a Within Qualifier" % stop_time)
 
     def __str__(self):
         return "START %s STOP %s" % (self.start_time, self.stop_time)
diff --git a/stix2/test/test_observed_data.py b/stix2/test/test_observed_data.py
index 75f3070..d5641e7 100644
--- a/stix2/test/test_observed_data.py
+++ b/stix2/test/test_observed_data.py
@@ -225,7 +225,7 @@ def test_parse_autonomous_system_valid(data):
 
 @pytest.mark.parametrize("data", [
     """{
-        "type": "email-address",
+        "type": "email-addr",
         "value": "john@example.com",
         "display_name": "John Doe",
         "belongs_to_ref": "0"
@@ -233,7 +233,7 @@ def test_parse_autonomous_system_valid(data):
 ])
 def test_parse_email_address(data):
     odata = stix2.parse_observable(data, {"0": "user-account"})
-    assert odata.type == "email-address"
+    assert odata.type == "email-addr"
 
     odata_str = re.compile('"belongs_to_ref": "0"', re.DOTALL).sub('"belongs_to_ref": "3"', data)
     with pytest.raises(stix2.exceptions.InvalidObjRefError):
diff --git a/stix2/test/test_pattern_expressions.py b/stix2/test/test_pattern_expressions.py
index fdfb1ee..2e8495b 100644
--- a/stix2/test/test_pattern_expressions.py
+++ b/stix2/test/test_pattern_expressions.py
@@ -26,18 +26,32 @@ def test_boolean_expression_with_parentheses():
     assert str(exp) == "(email-message:from_ref.value MATCHES '.+\\\\@example\\\\.com$' AND email-message:body_multipart[*].body_raw_ref.name MATCHES '^Final Report.+\\\\.exe$')"  # noqa
 
 
+def test_hash_followed_by_registryKey_expression_python_constant():
+    hash_exp = stix2.EqualityComparisonExpression("file:hashes.MD5",
+                                                  stix2.HashConstant("79054025255fb1a26e4bc422aef54eb4", "MD5"))
+    o_exp1 = stix2.ObservableExpression(hash_exp)
+    reg_exp = stix2.EqualityComparisonExpression(stix2.ObjectPath("windows-registry-key", ["key"]),
+                                                 stix2.StringConstant("HKEY_LOCAL_MACHINE\\foo\\bar"))
+    o_exp2 = stix2.ObservableExpression(reg_exp)
+    fb_exp = stix2.FollowedByObservableExpression([o_exp1, o_exp2])
+    para_exp = stix2.ParentheticalExpression(fb_exp)
+    qual_exp = stix2.WithinQualifier(300)
+    exp = stix2.QualifiedObservationExpression(para_exp, qual_exp)
+    assert str(exp) == "([file:hashes.MD5 = '79054025255fb1a26e4bc422aef54eb4'] FOLLOWEDBY [windows-registry-key:key = 'HKEY_LOCAL_MACHINE\\\\foo\\\\bar']) WITHIN 300 SECONDS"  # noqa
+
+
 def test_hash_followed_by_registryKey_expression():
     hash_exp = stix2.EqualityComparisonExpression("file:hashes.MD5",
                                                   stix2.HashConstant("79054025255fb1a26e4bc422aef54eb4", "MD5"))
     o_exp1 = stix2.ObservableExpression(hash_exp)
-    reg_exp = stix2.EqualityComparisonExpression("win-registry-key:key",
+    reg_exp = stix2.EqualityComparisonExpression(stix2.ObjectPath("windows-registry-key", ["key"]),
                                                  stix2.StringConstant("HKEY_LOCAL_MACHINE\\foo\\bar"))
     o_exp2 = stix2.ObservableExpression(reg_exp)
     fb_exp = stix2.FollowedByObservableExpression([o_exp1, o_exp2])
     para_exp = stix2.ParentheticalExpression(fb_exp)
     qual_exp = stix2.WithinQualifier(stix2.IntegerConstant(300))
     exp = stix2.QualifiedObservationExpression(para_exp, qual_exp)
-    assert str(exp) == "([file:hashes.MD5 = '79054025255fb1a26e4bc422aef54eb4'] FOLLOWEDBY [win-registry-key:key = 'HKEY_LOCAL_MACHINE\\\\foo\\\\bar']) WITHIN 300 SECONDS"  # noqa
+    assert str(exp) == "([file:hashes.MD5 = '79054025255fb1a26e4bc422aef54eb4'] FOLLOWEDBY [windows-registry-key:key = 'HKEY_LOCAL_MACHINE\\\\foo\\\\bar']) WITHIN 300 SECONDS"  # noqa
 
 
 def test_file_observable_expression():
@@ -82,7 +96,7 @@ def test_root_types():
 
 def test_artifact_payload():
     exp1 = stix2.EqualityComparisonExpression("artifact:mime_type",
-                                              stix2.StringConstant("application/vnd.tcpdump.pcap"))
+                                              "application/vnd.tcpdump.pcap")
     exp2 = stix2.MatchesComparisonExpression("artifact:payload_bin",
                                              stix2.StringConstant("\\xd4\\xc3\\xb2\\xa1\\x02\\x00\\x04\\x00"))
     and_exp = stix2.AndBooleanExpression([exp1, exp2])
@@ -90,8 +104,67 @@ def test_artifact_payload():
     assert str(exp) == "[artifact:mime_type = 'application/vnd.tcpdump.pcap' AND artifact:payload_bin MATCHES '\\\\xd4\\\\xc3\\\\xb2\\\\xa1\\\\x02\\\\x00\\\\x04\\\\x00']"  # noqa
 
 
+def test_greater_than_python_constant():
+    exp1 = stix2.GreaterThanComparisonExpression("file:extensions.windows-pebinary-ext.sections[*].entropy",
+                                                 7.0)
+    exp = stix2.ObservableExpression(exp1)
+    assert str(exp) == "[file:extensions.windows-pebinary-ext.sections[*].entropy > 7.0]"
+
+
 def test_greater_than():
     exp1 = stix2.GreaterThanComparisonExpression("file:extensions.windows-pebinary-ext.sections[*].entropy",
                                                  stix2.FloatConstant(7.0))
     exp = stix2.ObservableExpression(exp1)
     assert str(exp) == "[file:extensions.windows-pebinary-ext.sections[*].entropy > 7.0]"
+
+
+def test_and_observable_expression():
+    exp1 = stix2.AndBooleanExpression([stix2.EqualityComparisonExpression("user-account:account_type",
+                                                                          "unix"),
+                                       stix2.EqualityComparisonExpression("user-account:user_id",
+                                                                          stix2.StringConstant("1007")),
+                                       stix2.EqualityComparisonExpression("user-account:account_login",
+                                                                          "Peter")])
+    exp2 = stix2.AndBooleanExpression([stix2.EqualityComparisonExpression("user-account:account_type",
+                                                                          "unix"),
+                                       stix2.EqualityComparisonExpression("user-account:user_id",
+                                                                          stix2.StringConstant("1008")),
+                                       stix2.EqualityComparisonExpression("user-account:account_login",
+                                                                          "Paul")])
+    exp3 = stix2.AndBooleanExpression([stix2.EqualityComparisonExpression("user-account:account_type",
+                                                                          "unix"),
+                                       stix2.EqualityComparisonExpression("user-account:user_id",
+                                                                          stix2.StringConstant("1009")),
+                                       stix2.EqualityComparisonExpression("user-account:account_login",
+                                                                          "Mary")])
+    exp = stix2.AndObservableExpression([stix2.ObservableExpression(exp1),
+                                         stix2.ObservableExpression(exp2),
+                                         stix2.ObservableExpression(exp3)])
+    assert str(exp) == "[user-account:account_type = 'unix' AND user-account:user_id = '1007' AND user-account:account_login = 'Peter'] AND [user-account:account_type = 'unix' AND user-account:user_id = '1008' AND user-account:account_login = 'Paul'] AND [user-account:account_type = 'unix' AND user-account:user_id = '1009' AND user-account:account_login = 'Mary']"  # noqa
+
+
+def test_hex():
+    exp_and = stix2.AndBooleanExpression([stix2.EqualityComparisonExpression("file:mime_type",
+                                                                             "image/bmp"),
+                                          stix2.EqualityComparisonExpression("file:magic_number_hex",
+                                                                             stix2.HexConstant("ffd8"))])
+    exp = stix2.ObservableExpression(exp_and)
+    assert str(exp) == "[file:mime_type = 'image/bmp' AND file:magic_number_hex = h'ffd8']"
+
+
+def test_multiple_qualifiers():
+    exp_and = stix2.AndBooleanExpression([stix2.EqualityComparisonExpression("network-traffic:dst_ref.type",
+                                                                             "domain-name"),
+                                          stix2.EqualityComparisonExpression("network-traffic:dst_ref.value",
+                                                                             "example.com")])
+    exp_ob = stix2.ObservableExpression(exp_and)
+    qual_rep = stix2.RepeatQualifier(5)
+    qual_within = stix2.WithinQualifier(stix2.IntegerConstant(1800))
+    exp = stix2.QualifiedObservationExpression(stix2.QualifiedObservationExpression(exp_ob, qual_rep), qual_within)
+    assert str(exp) == "[network-traffic:dst_ref.type = 'domain-name' AND network-traffic:dst_ref.value = 'example.com'] REPEATS 5 TIMES WITHIN 1800 SECONDS"  # noqa
+
+
+def test_set_op():
+    exp = stix2.ObservableExpression(stix2.IsSubsetComparisonExpression("network-traffic:dst_ref.value",
+                                                                        "2001:0db8:dead:beef:0000:0000:0000:0000/64"))
+    assert str(exp) == "[network-traffic:dst_ref.value ISSUBSET '2001:0db8:dead:beef:0000:0000:0000:0000/64']"