diff --git a/Gedcomx.Model.Test/AgentTest.cs b/Gedcomx.Model.Test/AgentTest.cs
index 1f0a1c1..9079e59 100644
--- a/Gedcomx.Model.Test/AgentTest.cs
+++ b/Gedcomx.Model.Test/AgentTest.cs
@@ -31,8 +31,11 @@ public void AgentObjectInitialization()
         {
             var sut = new Agent
             {
+                // ExtensibleData
                 Id = "A-1",
+                // HypermediaEnabledData
                 Links = { new Link(), { "rel", new Uri("https://www.familysearch.org/platform/collections/tree") }, { "rel", "template" } },
+                // Agent
                 Accounts = { new OnlineAccount() },
                 Addresses = { new Address() },
                 Emails = { "example@example.org" },
@@ -77,20 +80,7 @@ private static void VerifyXmlSerialization(Agent sut)
 
             stream.Seek(0, SeekOrigin.Begin);
             var result = new StreamReader(stream).ReadToEnd();
-            Assert.That(result, Does.Contain("<agent "));
-            Assert.That(result, Does.Contain("xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\""));
-            Assert.That(result, Does.Contain("xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\""));
-            Assert.That(result, Does.Contain("xmlns=\"http://gedcomx.org/v1/\""));
-            Assert.That(result.Contains("id"), Is.EqualTo(sut.Id != null));
-            Assert.That(result.Contains("<link"), Is.EqualTo(sut.AnyLinks()));
-            Assert.That(result.Contains("<account"), Is.EqualTo(sut.AnyAccounts()));
-            Assert.That(result.Contains("<address"), Is.EqualTo(sut.AnyAddresses()));
-            Assert.That(result.Contains("<email"), Is.EqualTo(sut.AnyEmails()));
-            Assert.That(result.Contains("<homepage"), Is.EqualTo(sut.Homepage != null));
-            Assert.That(result.Contains("<identifier"), Is.EqualTo(sut.AnyIdentifiers()));
-            Assert.That(result.Contains("<name"), Is.EqualTo(sut.AnyNames()));
-            Assert.That(result.Contains("<openid"), Is.EqualTo(sut.Openid != null));
-            Assert.That(result.Contains("<phone"), Is.EqualTo(sut.AnyPhones()));
+            result.ShouldContain(sut);
         }
 
         private static void VerifyJsonSerialization(Agent sut)
diff --git a/Gedcomx.Model.Test/FactTest.cs b/Gedcomx.Model.Test/FactTest.cs
new file mode 100644
index 0000000..baf48fd
--- /dev/null
+++ b/Gedcomx.Model.Test/FactTest.cs
@@ -0,0 +1,80 @@
+using System.Xml.Serialization;
+
+using Gx.Common;
+using Gx.Conclusion;
+using Gx.Records;
+using Gx.Source;
+using Gx.Types;
+
+using Newtonsoft.Json;
+
+using NUnit.Framework;
+
+namespace Gedcomx.Model.Test
+{
+    /// <summary>
+    /// Test calss for <see cref="Fact"/>
+    /// </summary>
+    [TestFixture]
+    public class FactTest
+    {
+        [Test]
+        public void FactEmpty()
+        {
+            var sut = new Fact();
+
+            VerifyXmlSerialization(sut);
+            VerifyJsonSerialization(sut);
+        }
+
+        [Test]
+        public void FactFilled()
+        {
+            var sut = new Fact
+            {
+                // ExtensibleData
+                Id = "F-1",
+                // Conclusion
+                KnownConfidence = ConfidenceLevel.Medium,
+                SortKey = "sort key",
+                Lang = "lang",
+                Attribution = new Attribution(),
+                Sources = { new SourceReference(), new SourceDescription() { Id = "S-1" } },
+                Analysis = new ResourceReference(),
+                Notes = { new Note() },
+                // Fact
+                Primary = true,
+                KnownType = FactType.Adoption,
+                Date = new DateInfo(),
+                Place = new PlaceReference(),
+                Value = "value",
+                Qualifiers = { new Qualifier() },
+                Fields = { new Field() }
+            };
+
+            VerifyXmlSerialization(sut);
+            VerifyJsonSerialization(sut);
+        }
+
+        private static void VerifyXmlSerialization(Fact sut)
+        {
+            var serializer = new XmlSerializer(typeof(Fact));
+            using var stream = new MemoryStream();
+            serializer.Serialize(stream, sut);
+
+            stream.Seek(0, SeekOrigin.Begin);
+            var result = new StreamReader(stream).ReadToEnd();
+            result.ShouldContain(sut);
+        }
+
+        private static void VerifyJsonSerialization(Fact sut)
+        {
+            JsonSerializerSettings jsonSettings = new()
+            {
+                NullValueHandling = NullValueHandling.Ignore
+            };
+
+            Assert.DoesNotThrow(() => JsonConvert.DeserializeObject<Fact>(JsonConvert.SerializeObject(sut, jsonSettings), jsonSettings));
+        }
+    }
+}
diff --git a/Gedcomx.Model.Test/GedcomxTest.cs b/Gedcomx.Model.Test/GedcomxTest.cs
index 0c0bace..717fd6e 100644
--- a/Gedcomx.Model.Test/GedcomxTest.cs
+++ b/Gedcomx.Model.Test/GedcomxTest.cs
@@ -56,10 +56,12 @@ public void EmmaBocockExampleTest()
                 Created = DateTime.Parse("1843-07-27"),
                 Repository = repository
             };
-            Fact birth = new Fact()
-            .SetType(FactType.Birth)
-            .SetDate(new DateInfo().SetOriginal("23 June 1843"))
-            .SetPlace(new PlaceReference().SetOriginal("Broadfield Bar, Abbeydale Road, Ecclesall-Bierlow, York, England, United Kingdom"));
+            Fact birth = new()
+            {
+                KnownType = FactType.Birth,
+                Date = new DateInfo().SetOriginal("23 June 1843"),
+                Place = new PlaceReference().SetOriginal("Broadfield Bar, Abbeydale Road, Ecclesall-Bierlow, York, England, United Kingdom")
+            };
             Person emma = (Person)new Person().SetName("Emma Bocock").SetGender(GenderType.Female).SetFact(birth).SetExtracted(true).SetSource(sourceDescription).SetId("P-1");
             Person father = (Person)new Person().SetName("William Bocock").SetFact(new Fact().SetType(FactType.Occupation).SetValue("Toll Collector")).SetExtracted(true).SetSource(sourceDescription).SetId("P-2");
             Person mother = (Person)new Person().SetName("Sarah Bocock formerly Brough").SetExtracted(true).SetSource(sourceDescription).SetId("P-3");
@@ -148,22 +150,28 @@ public void SamuelHamExampleTest()
             };
 
             //the marriage fact.
-            Fact marriage = new Fact()
-              .SetType(FactType.Marriage)
-              .SetDate(new DateInfo().SetOriginal("3 November 1828").SetFormal("+1828-11-03"))
-              .SetPlace(new PlaceReference().SetOriginal("Wilton St George, Wilton, Somerset, England"));
+            Fact marriage = new()
+            {
+                KnownType = FactType.Marriage,
+                Date = new DateInfo().SetOriginal("3 November 1828").SetFormal("+1828-11-03"),
+                Place = new PlaceReference().SetOriginal("Wilton St George, Wilton, Somerset, England")
+            };
 
             //the groom's residence.
-            Fact samsResidence = new Fact()
-              .SetType(FactType.Residence)
-              .SetDate(new DateInfo().SetOriginal("3 November 1828").SetFormal("+1828-11-03"))
-              .SetPlace(new PlaceReference().SetOriginal("parish of Honiton, Devon, England"));
+            Fact samsResidence = new()
+            {
+                KnownType = FactType.Residence,
+                Date = new DateInfo().SetOriginal("3 November 1828").SetFormal("+1828-11-03"),
+                Place = new PlaceReference().SetOriginal("parish of Honiton, Devon, England")
+            };
 
             //the groom's residence.
-            Fact lizsResidence = new Fact()
-              .SetType(FactType.Residence)
-              .SetDate(new DateInfo().SetOriginal("3 November 1828").SetFormal("+1828-11-03"))
-              .SetPlace(new PlaceReference().SetOriginal("parish of Wilton, Somerset, England"));
+            Fact lizsResidence = new()
+            {
+                KnownType = FactType.Residence,
+                Date = new DateInfo().SetOriginal("3 November 1828").SetFormal("+1828-11-03"),
+                Place = new PlaceReference().SetOriginal("parish of Wilton, Somerset, England")
+            };
 
             //the groom
             Person sam = (Person)new Person().SetName("Samuel Ham").SetGender(GenderType.Male).SetFact(samsResidence).SetExtracted(true).SetSource(transcriptionDescription).SetId("P-1");
@@ -568,20 +576,26 @@ public void WongAloiauExampleTest()
             };
 
             //the birth.
-            Fact birth = new Fact()
-              .SetType(FactType.Birth)
-              .SetDate(new DateInfo().SetOriginal("former Qing 1848 year 11th month 22nd day 23-1 hour").SetFormal("+1848-11-22"))
-              .SetPlace(new PlaceReference().SetOriginal("Pun Sha Village, See Dai Doo, Chung Shan, Guangdong, China"));
+            Fact birth = new()
+            {
+                KnownType = FactType.Birth,
+                Date = new DateInfo().SetOriginal("former Qing 1848 year 11th month 22nd day 23-1 hour").SetFormal("+1848-11-22"),
+                Place = new PlaceReference().SetOriginal("Pun Sha Village, See Dai Doo, Chung Shan, Guangdong, China")
+            };
 
             //the death.
-            Fact death = new Fact()
-              .SetType(FactType.Death)
-              .SetDate(new DateInfo().SetOriginal("Republic of China year 1920 year 7th mo. 12th day 11-13 hour").SetFormal("+1920-08-03"));
+            Fact death = new()
+            {
+                KnownType = FactType.Death,
+                Date = new DateInfo().SetOriginal("Republic of China year 1920 year 7th mo. 12th day 11-13 hour").SetFormal("+1920-08-03")
+            };
 
             //the burial.
-            Fact burial = new Fact()
-              .SetType(FactType.Burial)
-              .SetPlace(new PlaceReference().SetOriginal("Lin Yee Chung Cemetery, Honolulu, Oahu, Hawaii"));
+            Fact burial = new()
+            {
+                KnownType = FactType.Burial,
+                Place = new PlaceReference().SetOriginal("Lin Yee Chung Cemetery, Honolulu, Oahu, Hawaii")
+            };
 
             //the principal person
             Person aloiau = (Person)new Person().SetName("WONG Aloiau").SetGender(GenderType.Male).SetFact(birth).SetFact(death).SetFact(burial).SetExtracted(true).SetSource(translationDescription).SetId("P-1");
@@ -711,31 +725,23 @@ private static Person CreateGeorge(PlaceDescription birthPlace, PlaceDescription
             Person person = new();
             person.SetGender(new Gender(GenderType.Male));
 
-            Fact fact = new();
-            fact.SetId("123");
-            fact.SetType(FactType.Birth);
-
-            fact.SetDate(new DateInfo());
-            fact.Date.SetOriginal("February 22, 1732");
-            fact.Date.SetFormal("+1732-02-22");
-
-            fact.SetPlace(new PlaceReference());
-            fact.Place.SetOriginal(birthPlace.Names[0].Value.ToLower());
-            fact.Place.DescriptionRef = "#" + birthPlace.Id;
+            Fact fact = new()
+            {
+                Id = "123",
+                KnownType = FactType.Birth,
+                Date = new DateInfo().SetOriginal("February 22, 1732").SetFormal("+1732-02-22"),
+                Place = new PlaceReference().SetOriginal(birthPlace.Names[0].Value.ToLower()).SetDescription(birthPlace)
+            };
 
             person.AddFact(fact);
 
-            fact = new Fact();
-            fact.SetId("456");
-            fact.SetType(FactType.Death);
-
-            fact.SetDate(new DateInfo());
-            fact.Date.SetOriginal("December 14, 1799");
-            fact.Date.SetFormal("+1799-12-14T22:00:00");
-
-            fact.SetPlace(new PlaceReference());
-            fact.Place.SetOriginal(deathPlace.Names[0].Value.ToLower());
-            fact.Place.DescriptionRef = "#" + deathPlace.Id;
+            fact = new()
+            {
+                Id = "456",
+                KnownType = FactType.Death,
+                Date = new DateInfo().SetOriginal("December 14, 1799").SetFormal("+1799-12-14T22:00:00"),
+                Place = new PlaceReference().SetOriginal(deathPlace.Names[0].Value.ToLower()).SetDescription(deathPlace)
+            };
 
             person.AddFact(fact);
 
@@ -768,31 +774,23 @@ private static Person CreateMartha(PlaceDescription birthPlace, PlaceDescription
             Person person = new();
             person.SetGender(new Gender(GenderType.Male));
 
-            Fact fact = new();
-            fact.SetId("321");
-            fact.SetType(FactType.Birth);
-
-            fact.SetDate(new DateInfo());
-            fact.Date.SetOriginal("June 2, 1731");
-            fact.Date.SetFormal("+1731-06-02");
-
-            fact.SetPlace(new PlaceReference());
-            fact.Place.SetOriginal(birthPlace.Names[0].Value.ToLower());
-            fact.Place.DescriptionRef = "#" + birthPlace.Id;
+            Fact fact = new()
+            {
+                Id = "321",
+                KnownType = FactType.Birth,
+                Date = new DateInfo().SetOriginal("June 2, 1731").SetFormal("+1731-06-02"),
+                Place = new PlaceReference().SetOriginal(birthPlace.Names[0].Value.ToLower()).SetDescription(birthPlace)
+            };
 
             person.AddFact(fact);
 
-            fact = new Fact();
-            fact.SetId("654");
-            fact.SetType(FactType.Death);
-
-            fact.SetDate(new DateInfo());
-            fact.Date.SetOriginal("May 22, 1802");
-            fact.Date.SetFormal("+1802-05-22");
-
-            fact.SetPlace(new PlaceReference());
-            fact.Place.SetOriginal(deathPlace.Names[0].Value.ToLower());
-            fact.Place.DescriptionRef = "#" + deathPlace.Id;
+            fact = new()
+            {
+                Id = "654",
+                KnownType = FactType.Death,
+                Date = new DateInfo().SetOriginal("May 22, 1802").SetFormal("+1802-05-22"),
+                Place = new PlaceReference().SetOriginal(deathPlace.Names[0].Value.ToLower()).SetDescription(deathPlace)
+            };
 
             person.AddFact(fact);
 
diff --git a/Gedcomx.Model.Test/OnlineAccountTest.cs b/Gedcomx.Model.Test/OnlineAccountTest.cs
index cf2e417..6cae222 100644
--- a/Gedcomx.Model.Test/OnlineAccountTest.cs
+++ b/Gedcomx.Model.Test/OnlineAccountTest.cs
@@ -1,5 +1,7 @@
 using System.Xml.Serialization;
 
+using Gx.Agent;
+
 using Newtonsoft.Json;
 
 using NUnit.Framework;
@@ -7,7 +9,7 @@
 namespace Gedcomx.Model.Test
 {
     /// <summary>
-    /// Test calss for <see cref="Gx.Agent.OnlineAccount"/>
+    /// Test calss for <see cref="OnlineAccount"/>
     /// </summary>
     [TestFixture]
     public class OnlineAccountTest
@@ -15,7 +17,7 @@ public class OnlineAccountTest
         [Test]
         public void OnlineAccountEmpty()
         {
-            var sut = new Gx.Agent.OnlineAccount();
+            var sut = new OnlineAccount();
 
             VerifyXmlSerialization(sut);
             VerifyJsonSerialization(sut);
@@ -24,9 +26,11 @@ public void OnlineAccountEmpty()
         [Test]
         public void OnlineAccountFilled()
         {
-            var sut = new Gx.Agent.OnlineAccount
+            var sut = new OnlineAccount
             {
+                // ExtensibleData
                 Id = "O-1",
+                // OnlineAccount
                 AccountName = "Peter Pan",
                 ServiceHomepage = new Gx.Common.ResourceReference()
             };
@@ -35,30 +39,25 @@ public void OnlineAccountFilled()
             VerifyJsonSerialization(sut);
         }
 
-        private static void VerifyXmlSerialization(Gx.Agent.OnlineAccount sut)
+        private static void VerifyXmlSerialization(OnlineAccount sut)
         {
-            var serializer = new XmlSerializer(typeof(Gx.Agent.OnlineAccount));
+            var serializer = new XmlSerializer(typeof(OnlineAccount));
             using var stream = new MemoryStream();
             serializer.Serialize(stream, sut);
 
             stream.Seek(0, SeekOrigin.Begin);
             var result = new StreamReader(stream).ReadToEnd();
-            Assert.That(result, Does.Contain("<OnlineAccount "));
-            Assert.That(result, Does.Contain("xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\""));
-            Assert.That(result, Does.Contain("xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\""));
-            Assert.That(result.Contains("id"), Is.EqualTo(sut.Id != null));
-            Assert.That(result.Contains("accountName"), Is.EqualTo(sut.AccountName != null));
-            Assert.That(result.Contains("serviceHomepage"), Is.EqualTo(sut.ServiceHomepage != null));
+            result.ShouldContain(sut);
         }
 
-        private static void VerifyJsonSerialization(Gx.Agent.OnlineAccount sut)
+        private static void VerifyJsonSerialization(OnlineAccount sut)
         {
             JsonSerializerSettings jsonSettings = new()
             {
                 NullValueHandling = NullValueHandling.Ignore
             };
 
-            Assert.DoesNotThrow(() => JsonConvert.DeserializeObject<Gx.Agent.OnlineAccount>(JsonConvert.SerializeObject(sut, jsonSettings), jsonSettings));
+            Assert.DoesNotThrow(() => JsonConvert.DeserializeObject<OnlineAccount>(JsonConvert.SerializeObject(sut, jsonSettings), jsonSettings));
         }
     }
 }
diff --git a/Gedcomx.Model.Test/SourceDescriptionTest.cs b/Gedcomx.Model.Test/SourceDescriptionTest.cs
index c50045e..8de8cdf 100644
--- a/Gedcomx.Model.Test/SourceDescriptionTest.cs
+++ b/Gedcomx.Model.Test/SourceDescriptionTest.cs
@@ -33,8 +33,11 @@ public void AgentObjectInitialization()
         {
             var sut = new SourceDescription
             {
+                // ExtensibleData
                 Id = "A-1",
+                // HypermediaEnabledData
                 Links = { new Link(), { "rel", new Uri("https://www.familysearch.org/platform/collections/tree") }, { "rel", "template" } },
+                // SourceDescription
                 About = "about text",
                 Lang = "language",
                 MediaType = "type of media",
@@ -67,26 +70,7 @@ private static void VerifyXmlSerialization(SourceDescription sut)
 
             stream.Seek(0, SeekOrigin.Begin);
             var result = new StreamReader(stream).ReadToEnd();
-            Assert.That(result, Does.Contain("<sourceDescription "));
-            Assert.That(result.Contains("<link"), Is.EqualTo(sut.AnyLinks()));
-            Assert.That(result.Contains("about="), Is.EqualTo(sut.About != null));
-            Assert.That(result.Contains("lang="), Is.EqualTo(sut.Lang != null));
-            Assert.That(result.Contains("mediaType="), Is.EqualTo(sut.MediaType != null));
-            Assert.That(result.Contains("sortKey="), Is.EqualTo(sut.SortKey != null));
-            Assert.That(result.Contains("resourceType="), Is.EqualTo(sut.ResourceType != null));
-            Assert.That(result.Contains("<citation"), Is.EqualTo(sut.AnyCitations()));
-            Assert.That(result.Contains("<mediator"), Is.EqualTo(sut.Mediator != null));
-            Assert.That(result.Contains("<source "), Is.EqualTo(sut.AnySources()));
-            Assert.That(result.Contains("<analysis"), Is.EqualTo(sut.Analysis != null));
-            Assert.That(result.Contains("<componentOf "), Is.EqualTo(sut.ComponentOf != null));
-            Assert.That(result.Contains("<title>"), Is.EqualTo(sut.AnyTitles()));
-            Assert.That(result.Contains("<titleLabel"), Is.EqualTo(sut.TitleLabel != null));
-            Assert.That(result.Contains("<note"), Is.EqualTo(sut.AnyNotes()));
-            Assert.That(result.Contains("<description"), Is.EqualTo(sut.AnyDescriptions()));
-            Assert.That(result.Contains("<identifier"), Is.EqualTo(sut.AnyIdentifiers()));
-            Assert.That(result.Contains("<coverage"), Is.EqualTo(sut.AnyCoverage()));
-            Assert.That(result.Contains("<rights"), Is.EqualTo(sut.AnyRights()));
-            Assert.That(result.Contains("<field"), Is.EqualTo(sut.AnyFields()));
+            result.ShouldContain(sut);
         }
 
         private static void VerifyJsonSerialization(SourceDescription sut)
diff --git a/Gedcomx.Model.Test/XmlAssertions.cs b/Gedcomx.Model.Test/XmlAssertions.cs
new file mode 100644
index 0000000..031fee3
--- /dev/null
+++ b/Gedcomx.Model.Test/XmlAssertions.cs
@@ -0,0 +1,106 @@
+using Gx.Agent;
+using Gx.Common;
+using Gx.Conclusion;
+using Gx.Links;
+using Gx.Source;
+
+using NUnit.Framework;
+
+namespace Gedcomx.Model.Test
+{
+    public static class XmlAssertions
+    {
+        public static void ShouldContain(this string result, Agent agent)
+        {
+            Assert.That(result, Does.Contain("<agent "));
+            Assert.That(result, Does.Contain("xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\""));
+            Assert.That(result, Does.Contain("xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\""));
+            Assert.That(result, Does.Contain("xmlns=\"http://gedcomx.org/v1/\""));
+            Assert.That(result.Contains("<account"), Is.EqualTo(agent.AnyAccounts()));
+            Assert.That(result.Contains("<address"), Is.EqualTo(agent.AnyAddresses()));
+            Assert.That(result.Contains("<email"), Is.EqualTo(agent.AnyEmails()));
+            Assert.That(result.Contains("<homepage"), Is.EqualTo(agent.Homepage != null));
+            Assert.That(result.Contains("<identifier"), Is.EqualTo(agent.AnyIdentifiers()));
+            Assert.That(result.Contains("<name"), Is.EqualTo(agent.AnyNames()));
+            Assert.That(result.Contains("<openid"), Is.EqualTo(agent.Openid != null));
+            Assert.That(result.Contains("<phone"), Is.EqualTo(agent.AnyPhones()));
+            result.ShouldContain(agent as HypermediaEnabledData);
+        }
+
+        public static void ShouldContain(this string result, SourceDescription sourceDescription)
+        {
+            Assert.That(result, Does.Contain("<sourceDescription "));
+            Assert.That(result, Does.Contain("xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\""));
+            Assert.That(result, Does.Contain("xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\""));
+            Assert.That(result, Does.Contain("xmlns=\"http://gedcomx.org/v1/\""));
+            Assert.That(result.Contains("about="), Is.EqualTo(sourceDescription.About != null));
+            Assert.That(result.Contains("lang="), Is.EqualTo(sourceDescription.Lang != null));
+            Assert.That(result.Contains("mediaType="), Is.EqualTo(sourceDescription.MediaType != null));
+            Assert.That(result.Contains("sortKey="), Is.EqualTo(sourceDescription.SortKey != null));
+            Assert.That(result.Contains("resourceType="), Is.EqualTo(sourceDescription.ResourceType != null));
+            Assert.That(result.Contains("<citation"), Is.EqualTo(sourceDescription.AnyCitations()));
+            Assert.That(result.Contains("<mediator"), Is.EqualTo(sourceDescription.Mediator != null));
+            Assert.That(result.Contains("<source "), Is.EqualTo(sourceDescription.AnySources()));
+            Assert.That(result.Contains("<analysis"), Is.EqualTo(sourceDescription.Analysis != null));
+            Assert.That(result.Contains("<componentOf "), Is.EqualTo(sourceDescription.ComponentOf != null));
+            Assert.That(result.Contains("<title>"), Is.EqualTo(sourceDescription.AnyTitles()));
+            Assert.That(result.Contains("<titleLabel"), Is.EqualTo(sourceDescription.TitleLabel != null));
+            Assert.That(result.Contains("<note"), Is.EqualTo(sourceDescription.AnyNotes()));
+            Assert.That(result.Contains("<description"), Is.EqualTo(sourceDescription.AnyDescriptions()));
+            Assert.That(result.Contains("<identifier"), Is.EqualTo(sourceDescription.AnyIdentifiers()));
+            Assert.That(result.Contains("<coverage"), Is.EqualTo(sourceDescription.AnyCoverage()));
+            Assert.That(result.Contains("<rights"), Is.EqualTo(sourceDescription.AnyRights()));
+            Assert.That(result.Contains("<field"), Is.EqualTo(sourceDescription.AnyFields()));
+            result.ShouldContain(sourceDescription as HypermediaEnabledData);
+        }
+
+        public static void ShouldContain(this string result, Fact fact)
+        {
+            Assert.That(result, Does.Contain("<fact "));
+            Assert.That(result, Does.Contain("xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\""));
+            Assert.That(result, Does.Contain("xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\""));
+            Assert.That(result, Does.Contain("xmlns=\"http://gedcomx.org/v1/\""));
+            Assert.That(result.Contains("primary="), Is.EqualTo(fact.PrimarySpecified));
+            Assert.That(result.Contains("type="), Is.EqualTo(fact.Type != null));
+            Assert.That(result.Contains("<date"), Is.EqualTo(fact.Date != null));
+            Assert.That(result.Contains("<place"), Is.EqualTo(fact.Place != null));
+            Assert.That(result.Contains("<value"), Is.EqualTo(fact.Value != null));
+            Assert.That(result.Contains("<qualifier"), Is.EqualTo(fact.AnyQualifiers()));
+            Assert.That(result.Contains("<field"), Is.EqualTo(fact.AnyFields()));
+            result.ShouldContain(fact as Conclusion);
+        }
+
+        public static void ShouldContain(this string result, Conclusion conclusion)
+        {
+            Assert.That(result.Contains("confidence="), Is.EqualTo(conclusion.Confidence != null));
+            Assert.That(result.Contains("sortKey="), Is.EqualTo(conclusion.SortKey != null));
+            Assert.That(result.Contains("lang="), Is.EqualTo(conclusion.Lang != null));
+            Assert.That(result.Contains("<attribution"), Is.EqualTo(conclusion.Attribution != null));
+            Assert.That(result.Contains("<source"), Is.EqualTo(conclusion.AnySources()));
+            Assert.That(result.Contains("<analysis"), Is.EqualTo(conclusion.Analysis != null));
+            Assert.That(result.Contains("<note"), Is.EqualTo(conclusion.AnyNotes()));
+            result.ShouldContain(conclusion as HypermediaEnabledData);
+        }
+
+        public static void ShouldContain(this string result, HypermediaEnabledData hypermediaEnabledData)
+        {
+            Assert.That(result.Contains("<link"), Is.EqualTo(hypermediaEnabledData.AnyLinks()));
+            result.ShouldContain(hypermediaEnabledData as ExtensibleData);
+        }
+
+        public static void ShouldContain(this string result, OnlineAccount onlineAccount)
+        {
+            Assert.That(result, Does.Contain("<OnlineAccount "));
+            Assert.That(result, Does.Contain("xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\""));
+            Assert.That(result, Does.Contain("xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\""));
+            Assert.That(result.Contains("accountName"), Is.EqualTo(onlineAccount.AccountName != null));
+            Assert.That(result.Contains("serviceHomepage"), Is.EqualTo(onlineAccount.ServiceHomepage != null));
+            result.ShouldContain(onlineAccount as ExtensibleData);
+        }
+
+        public static void ShouldContain(this string result, ExtensibleData extensibleData)
+        {
+            Assert.That(result.Contains("id"), Is.EqualTo(extensibleData.Id != null));
+        }
+    }
+}
diff --git a/Gedcomx.Model/Conclusion.cs b/Gedcomx.Model/Conclusion.cs
index 60c350b..2564db0 100644
--- a/Gedcomx.Model/Conclusion.cs
+++ b/Gedcomx.Model/Conclusion.cs
@@ -4,12 +4,11 @@
 // Generated by <a href="http://enunciate.codehaus.org">Enunciate</a>.
 // </auto-generated>
 using System;
-using System.Collections.Generic;
+using System.Linq;
 
 using Gedcomx.Model.Util;
 
 using Gx.Common;
-using Gx.Model;
 using Gx.Source;
 using Gx.Types;
 
@@ -123,13 +122,18 @@ public System.Collections.Generic.List<Gx.Source.SourceReference> Sources
         {
             get
             {
-                return this._sources;
+                return this._sources ?? (_sources = new System.Collections.Generic.List<Gx.Source.SourceReference>());
             }
             set
             {
                 this._sources = value;
             }
         }
+        public bool ShouldSerializeSources() => AnySources();
+        public bool AnySources()
+        {
+            return _sources?.Any() ?? false;
+        }
         /// <summary>
         ///  A reference to the analysis document explaining the analysis that went into this conclusion.
         /// </summary>
@@ -155,13 +159,18 @@ public System.Collections.Generic.List<Gx.Common.Note> Notes
         {
             get
             {
-                return this._notes;
+                return this._notes ?? (_notes = new System.Collections.Generic.List<Gx.Common.Note>());
             }
             set
             {
                 this._notes = value;
             }
         }
+        public bool ShouldSerializeNotes() => AnyNotes();
+        public bool AnyNotes()
+        {
+            return _notes?.Any() ?? false;
+        }
 
         protected internal override void Embed(ExtensibleData conclusion)
         {
@@ -172,13 +181,11 @@ protected internal override void Embed(ExtensibleData conclusion)
             this._analysis = this._analysis == null ? value._analysis : this._analysis;
             if (value._notes != null)
             {
-                this._notes = this._notes == null ? new List<Note>() : this._notes;
-                this._notes.AddRange(value._notes);
+                this.Notes.AddRange(value._notes);
             }
             if (value._sources != null)
             {
-                this._sources = this._sources == null ? new List<SourceReference>() : this._sources;
-                this._sources.AddRange(value._sources);
+                this.Sources.AddRange(value._sources);
             }
             base.Embed(conclusion);
         }
@@ -219,17 +226,6 @@ public Conclusion SetConfidence(ConfidenceLevel confidence)
             return this;
         }
 
-        /**
-         * Build up this conclusion with a source reference.
-         *
-         * @param source The source description being referenced.
-         * @return this.
-         */
-        public Conclusion SetSource(SourceDescription source)
-        {
-            return SetSource(new SourceReference().SetDescription(source));
-        }
-
         /**
          * Build up this conclusion with a source reference.
          *
@@ -238,7 +234,10 @@ public Conclusion SetSource(SourceDescription source)
          */
         public Conclusion SetSource(SourceReference sourceReference)
         {
-            AddSource(sourceReference);
+            if (sourceReference != null)
+            {
+                Sources.Add(sourceReference);
+            }
             return this;
         }
 
@@ -250,7 +249,10 @@ public Conclusion SetSource(SourceReference sourceReference)
          */
         public Conclusion SetNote(Note note)
         {
-            AddNote(note);
+            if (note != null)
+            {
+                _notes.Add(note);
+            }
             return this;
         }
 
@@ -289,39 +291,5 @@ public Conclusion SetSortKey(String sortKey)
             SortKey = sortKey;
             return this;
         }
-
-        /**
-         * Add a source reference.
-         *
-         * @param source The source reference to be added.
-         */
-        public void AddSource(SourceReference source)
-        {
-            if (source != null)
-            {
-                if (_sources == null)
-                {
-                    _sources = new List<SourceReference>();
-                }
-                _sources.Add(source);
-            }
-        }
-
-        /**
-         * Add a note.
-         *
-         * @param note The note to be added.
-         */
-        public void AddNote(Note note)
-        {
-            if (note != null)
-            {
-                if (_notes == null)
-                {
-                    _notes = new List<Note>();
-                }
-                _notes.Add(note);
-            }
-        }
     }
 }
diff --git a/Gedcomx.Model/Fact.cs b/Gedcomx.Model/Fact.cs
index 6ec0fcc..0505a03 100644
--- a/Gedcomx.Model/Fact.cs
+++ b/Gedcomx.Model/Fact.cs
@@ -1,15 +1,17 @@
-using Gedcomx.Model.Rt;
-using Gedcomx.Model.Util;
-using Gx.Common;
-using Gx.Records;
-using Gx.Types;
-// <auto-generated>
+// <auto-generated>
 // 
 //
 // Generated by <a href="http://enunciate.codehaus.org">Enunciate</a>.
 // </auto-generated>
 using System;
-using System.Collections.Generic;
+using System.Linq;
+
+using Gedcomx.Model.Rt;
+using Gedcomx.Model.Util;
+
+using Gx.Common;
+using Gx.Records;
+using Gx.Types;
 
 namespace Gx.Conclusion
 {
@@ -44,12 +46,12 @@ public Fact(FactType factType, String value)
         }
 
         public Fact(FactType factType, String date, String place)
-            :this(factType, new DateInfo().SetOriginal(date), new PlaceReference().SetOriginal(place), null)
+            : this(factType, new DateInfo().SetOriginal(date), new PlaceReference().SetOriginal(place), null)
         {
         }
 
         public Fact(FactType factType, DateInfo date, PlaceReference place)
-            :this(factType, date, place, null)
+            : this(factType, date, place, null)
         {
         }
 
@@ -70,12 +72,12 @@ public bool Primary
         {
             get
             {
-                return this._primary.GetValueOrDefault();
+                return _primary.GetValueOrDefault();
             }
             set
             {
-                this._primary = value;
-                this._primarySpecified = true;
+                _primary = value;
+                _primarySpecified = true;
             }
         }
 
@@ -89,11 +91,11 @@ public bool PrimarySpecified
         {
             get
             {
-                return this._primarySpecified;
+                return _primarySpecified;
             }
             set
             {
-                this._primarySpecified = value;
+                _primarySpecified = value;
             }
         }
 
@@ -106,11 +108,11 @@ public string Type
         {
             get
             {
-                return this._type;
+                return _type;
             }
             set
             {
-                this._type = value;
+                _type = value;
             }
         }
 
@@ -123,11 +125,11 @@ public Gx.Types.FactType KnownType
         {
             get
             {
-                return XmlQNameEnumUtil.GetEnumValue<FactType>(this._type);
+                return XmlQNameEnumUtil.GetEnumValue<FactType>(_type);
             }
             set
             {
-                this._type = XmlQNameEnumUtil.GetNameValue(value);
+                _type = XmlQNameEnumUtil.GetNameValue(value);
             }
         }
         /// <summary>
@@ -139,11 +141,11 @@ public Gx.Conclusion.DateInfo Date
         {
             get
             {
-                return this._date;
+                return _date;
             }
             set
             {
-                this._date = value;
+                _date = value;
             }
         }
         /// <summary>
@@ -155,11 +157,11 @@ public Gx.Conclusion.PlaceReference Place
         {
             get
             {
-                return this._place;
+                return _place;
             }
             set
             {
-                this._place = value;
+                _place = value;
             }
         }
         /// <summary>
@@ -171,11 +173,11 @@ public string Value
         {
             get
             {
-                return this._value;
+                return _value;
             }
             set
             {
-                this._value = value;
+                _value = value;
             }
         }
         /// <summary>
@@ -187,13 +189,18 @@ public System.Collections.Generic.List<Gx.Common.Qualifier> Qualifiers
         {
             get
             {
-                return this._qualifiers;
+                return _qualifiers ?? (_qualifiers = new System.Collections.Generic.List<Gx.Common.Qualifier>());
             }
             set
             {
-                this._qualifiers = value;
+                _qualifiers = value;
             }
         }
+        public bool ShouldSerializeQualifiers() => AnyQualifiers();
+        public bool AnyQualifiers()
+        {
+            return _qualifiers?.Any() ?? false;
+        }
         /// <summary>
         ///  The references to the record fields being used as evidence.
         /// </summary>
@@ -203,13 +210,18 @@ public System.Collections.Generic.List<Gx.Records.Field> Fields
         {
             get
             {
-                return this._fields;
+                return _fields ?? (_fields = new System.Collections.Generic.List<Gx.Records.Field>());
             }
             set
             {
-                this._fields = value;
+                _fields = value;
             }
         }
+        public bool ShouldSerializeFields() => AnyFields();
+        public bool AnyFields()
+        {
+            return _fields?.Any() ?? false;
+        }
 
         /**
          * Accept a visitor.
@@ -301,7 +313,7 @@ public Fact SetValue(String value)
          */
         public Fact SetQualifier(Qualifier qualifier)
         {
-            AddQualifier(qualifier);
+            Qualifiers.Add(qualifier);
             return this;
         }
 
@@ -312,40 +324,12 @@ public Fact SetQualifier(Qualifier qualifier)
          * @return this.
          */
         public Fact SetField(Field field)
-        {
-            AddField(field);
-            return this;
-        }
-
-        /**
-         * Add a qualifier.
-         *
-         * @param qualifier The qualifier.
-         */
-        public void AddQualifier(Qualifier qualifier)
-        {
-            if (this._qualifiers == null)
-            {
-                this._qualifiers = new List<Qualifier>();
-            }
-            this._qualifiers.Add(qualifier);
-        }
-
-        /**
-         * Add a reference to the record field values being used as evidence.
-         *
-         * @param field The field to be added.
-         */
-        public void AddField(Field field)
         {
             if (field != null)
             {
-                if (_fields == null)
-                {
-                    _fields = new List<Field>();
-                }
-                _fields.Add(field);
+                Fields.Add(field);
             }
+            return this;
         }
     }
 }
diff --git a/Gedcomx.Model/SourceReference.cs b/Gedcomx.Model/SourceReference.cs
index b963d75..ebe7f0b 100644
--- a/Gedcomx.Model/SourceReference.cs
+++ b/Gedcomx.Model/SourceReference.cs
@@ -1,7 +1,4 @@
-using Gedcomx.Model.Rt;
-using Gx.Common;
-using Newtonsoft.Json;
-// <auto-generated>
+// <auto-generated>
 // 
 //
 // Generated by <a href="http://enunciate.codehaus.org">Enunciate</a>.
@@ -9,6 +6,12 @@
 using System;
 using System.Collections.Generic;
 
+using Gedcomx.Model.Rt;
+
+using Gx.Common;
+
+using Newtonsoft.Json;
+
 namespace Gx.Source
 {
 
@@ -28,6 +31,16 @@ public partial class SourceReference : Gx.Links.HypermediaEnabledData, IAttribut
         private Gx.Common.Attribution _attribution;
         private System.Collections.Generic.List<Gx.Common.Qualifier> _qualifiers;
         private System.Collections.Generic.List<Gx.Source.Tag> _tags;
+
+        /// <summary>
+        /// Build up this source reference with a <see cref="SourceDescription"/> reference.
+        /// </summary>
+        /// <param name="description">The source description being referenced.</param>
+        public static implicit operator SourceReference(SourceDescription description)
+        {
+            return new SourceReference().SetDescription(description);
+        }
+
         /// <summary>
         ///  A reference to a description of the source being referenced.
         /// </summary>
@@ -103,12 +116,12 @@ public void Accept(IGedcomxModelVisitor visitor)
             visitor.VisitSourceReference(this);
         }
 
-        /**
-         * Build up this source reference with a description reference.
-         *
-         * @param description The description.
-         * @return this.
-         */
+        /// <summary>
+        /// Build up this source reference with a <see cref="SourceDescription"/> reference.
+        /// </summary>
+        /// <param name="description">The source description being referenced.</param>
+        /// <returns>this.</returns>
+        /// <exception cref="ArgumentException">If the description Id is null.</exception>
         public SourceReference SetDescription(SourceDescription description)
         {
             if (description.Id == null)
diff --git a/Gedcomx.Rs.Api.Test/ParentsAndChildrenTest.cs b/Gedcomx.Rs.Api.Test/ParentsAndChildrenTest.cs
index 6b51bef..0b250d5 100644
--- a/Gedcomx.Rs.Api.Test/ParentsAndChildrenTest.cs
+++ b/Gedcomx.Rs.Api.Test/ParentsAndChildrenTest.cs
@@ -133,7 +133,7 @@ public void TestReadChildAndParentsRelationshipSourceReferences()
             var son = tree.AddPerson(TestBacking.GetCreateMalePerson());
             cleanup.Add(son);
             var temp = TestBacking.GetCreateChildAndParentsRelationship(father, mother, son);
-            temp.AddSource(TestBacking.GetPersonSourceReference());
+            temp.SetSource(TestBacking.GetPersonSourceReference());
             var relationship = (ChildAndParentsRelationshipState)tree.AddChildAndParentsRelationship(temp).Get();
             cleanup.Add(relationship);
             var state = relationship.LoadSourceReferences();
@@ -223,7 +223,7 @@ public void TestDeleteChildAndParentsRelationshipSourceReference()
             var son = tree.AddPerson(TestBacking.GetCreateMalePerson());
             cleanup.Add(son);
             var temp = TestBacking.GetCreateChildAndParentsRelationship(father, mother, son);
-            temp.AddSource(TestBacking.GetPersonSourceReference());
+            temp.SetSource(TestBacking.GetPersonSourceReference());
             var relationship = (ChildAndParentsRelationshipState)tree.AddChildAndParentsRelationship(temp).Get();
             cleanup.Add(relationship);