diff --git a/data4k/src/main/kotlin/dev/forkhandles/data/DataContainer.kt b/data4k/src/main/kotlin/dev/forkhandles/data/DataContainer.kt
index 23716c0..06d72c5 100644
--- a/data4k/src/main/kotlin/dev/forkhandles/data/DataContainer.kt
+++ b/data4k/src/main/kotlin/dev/forkhandles/data/DataContainer.kt
@@ -14,15 +14,34 @@ abstract class DataContainer<CONTENT>(
     private val getFn: (CONTENT, String) -> Any?,
     private val setFn: (CONTENT, String, Any?) -> Unit
 ) {
+    /** Required **/
 
-    //
-    // CORE FUNCTIONS - these are the only ones that should call the defined mappings
-    //
-
-    fun <OUT : Any?, NEXT> field(mapInFn: (OUT) -> NEXT, mapOutFn: (NEXT) -> OUT?) =
+    fun <OUT : Any?, NEXT> required(mapInFn: (OUT) -> NEXT, mapOutFn: (NEXT) -> OUT?) =
         property<NEXT, OUT, OUT>(mapInFn, mapOutFn)
 
-    fun <OUT : DataContainer<CONTENT>?> obj(mapInFn: (CONTENT) -> OUT, mapOutFn: (OUT) -> CONTENT?) =
+    fun <OUT : Any> required() = required<OUT, OUT>({ it }, { it })
+
+    fun <OUT, NEXT> required(mapInFn: (OUT) -> NEXT) = required(mapInFn) { error("no outbound mapping defined") }
+
+    fun <IN : Any, OUT : Value<IN>> required(factory: ValueFactory<OUT, IN>) =
+        required(factory::of) { it.value }
+
+    /** Optional **/
+
+    fun <OUT, NEXT : Any> optional(mapInFn: (OUT) -> NEXT) =
+        required<OUT, NEXT>(mapInFn) { error("no outbound mapping defined") }
+
+    fun <OUT, NEXT : Any> optional(mapInFn: (OUT) -> NEXT, mapOutFn: (NEXT) -> OUT?) =
+        required<OUT, NEXT?>(mapInFn) { it?.let(mapOutFn) }
+
+    fun <OUT> optional() = required<OUT, OUT?>({ it }, { it })
+
+    fun <IN : Any, OUT : Value<IN>> optional(factory: ValueFactory<OUT, IN>): DataProperty<DataContainer<CONTENT>, OUT?> =
+        required(factory::of) { it?.value }
+
+    /** Other **/
+
+    fun <OUT : DataContainer<CONTENT>> obj(mapInFn: (CONTENT) -> OUT, mapOutFn: (OUT) -> CONTENT?) =
         property<OUT, CONTENT, CONTENT>(mapInFn, mapOutFn)
 
     fun <OUT, IN> list(mapInFn: (IN) -> OUT, mapOutFn: (OUT) -> IN?) =
@@ -32,12 +51,8 @@ abstract class DataContainer<CONTENT>(
     // "PRE MAPPED" FUNCTIONS
     //
 
-    fun <OUT> field() = field<OUT, OUT>({ it }, { it })
-
     fun <OUT> list() = list<OUT, OUT>({ it }, { it })
 
-    fun <OUT, NEXT> field(mapInFn: (OUT) -> NEXT) = field(mapInFn) { error("no outbound mapping defined") }
-
     fun <IN, OUT> list(mapInFn: (IN) -> OUT) =
         list(mapInFn) { error("no outbound mapping defined") }
 
@@ -45,23 +60,15 @@ abstract class DataContainer<CONTENT>(
     fun <OUT : DataContainer<CONTENT>?> list(mapInFn: (CONTENT) -> OUT) =
         list(mapInFn) { it?.data }
 
-    fun <OUT : DataContainer<CONTENT>?> obj(mapInFn: (CONTENT) -> OUT) =
-        obj(mapInFn) { it?.data }
-
-    //
-    // VALUES4K functions
-    //
+    fun <OUT : DataContainer<CONTENT>> obj(mapInFn: (CONTENT) -> OUT) =
+        obj(mapInFn) { it.data }
 
-    fun <IN : Any, OUT : Value<IN>> field(factory: ValueFactory<OUT, IN>) =
-        field(factory::of) { it.value }
+    fun <OUT : DataContainer<CONTENT>> optionalObj(mapInFn: (CONTENT) -> OUT): DataProperty<DataContainer<CONTENT>, OUT?> =
+        property<OUT?, CONTENT, CONTENT>(mapInFn) { it?.data }
 
     fun <IN : Any, OUT : Value<IN>> list(factory: ValueFactory<OUT, IN>) =
         list(factory::of) { it.value }
 
-    //
-    // UTILITY FUNCTIONS - for comparisons etc
-    //
-
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
         if (javaClass != other?.javaClass) return false
diff --git a/data4k/src/test/kotlin/dev/forkhandles/lens/DataContainerContract.kt b/data4k/src/test/kotlin/dev/forkhandles/lens/DataContainerContract.kt
index faeef21..6b9d310 100644
--- a/data4k/src/test/kotlin/dev/forkhandles/lens/DataContainerContract.kt
+++ b/data4k/src/test/kotlin/dev/forkhandles/lens/DataContainerContract.kt
@@ -33,6 +33,7 @@ interface MainClassFields<T : SubClassFields> {
     var valueField: MyType
 
     var optionalField: String?
+    var optionalMappedField: Int?
     val optionalValueField: MyType?
     var optionalObjectField: T?
     val optionalListField: List<String>?
diff --git a/data4k/src/test/kotlin/dev/forkhandles/lens/JacksonDataContainerTest.kt b/data4k/src/test/kotlin/dev/forkhandles/lens/JacksonDataContainerTest.kt
index 1e72c73..259e328 100644
--- a/data4k/src/test/kotlin/dev/forkhandles/lens/JacksonDataContainerTest.kt
+++ b/data4k/src/test/kotlin/dev/forkhandles/lens/JacksonDataContainerTest.kt
@@ -8,31 +8,32 @@ import java.math.BigDecimal
 class JacksonDataContainerTest : DataContainerContract<JacksonDataContainerTest.SubNodeBacked>() {
 
     class SubNodeBacked(node: JsonNode) : JacksonDataContainer(node), SubClassFields {
-        override var stringField by field<String>()
-        override var noSuchField by field<String>()
+        override var stringField by required<String>()
+        override var noSuchField by required<String>()
     }
 
     class NodeBacked(node: JsonNode) : JacksonDataContainer(node), MainClassFields<SubNodeBacked> {
-        override var stringField by field<String>()
-        override var optionalField by field<String?>()
-        override var booleanField by field<Boolean>()
-        override var intField by field<Int>()
-        override var longField by field<Long>()
-        override var doubleField by field<Double>()
-        override var decimalField by field<BigDecimal>()
-        override var notAStringField by field<String>()
+        override var stringField by required<String>()
+        override var optionalField by optional<String>()
+        override var optionalMappedField by optional(String::toInt, Int::toString)
+        override var booleanField by required<Boolean>()
+        override var intField by required<Int>()
+        override var longField by required<Long>()
+        override var doubleField by required<Double>()
+        override var decimalField by required<BigDecimal>()
+        override var notAStringField by required<String>()
         override var listSubClassField by list(::SubNodeBacked)
         override var listField by list<String>()
         override var listIntsField by list<Int>()
         override var listValueField by list(MyType)
         override val listMapped by list(Int::toString)
         override var objectField by obj(::SubNodeBacked)
-        override var valueField by field(MyType)
-        override var mappedField by field(String::toInt, Int::toString)
+        override var valueField by required(MyType)
+        override var mappedField by required(String::toInt, Int::toString)
 
         override val optionalListField: List<String>? by list()
-        override var optionalObjectField by obj<SubNodeBacked?>(::SubNodeBacked)
-        override val optionalValueField: MyType? by field(MyType)
+        override var optionalObjectField by optionalObj(::SubNodeBacked)
+        override var optionalValueField by optional(MyType)
     }
 
     override fun container(input: Map<String, Any?>) = NodeBacked(ObjectMapper().valueToTree(input))
diff --git a/data4k/src/test/kotlin/dev/forkhandles/lens/MapDataContainerTest.kt b/data4k/src/test/kotlin/dev/forkhandles/lens/MapDataContainerTest.kt
index 2f7a511..497c718 100644
--- a/data4k/src/test/kotlin/dev/forkhandles/lens/MapDataContainerTest.kt
+++ b/data4k/src/test/kotlin/dev/forkhandles/lens/MapDataContainerTest.kt
@@ -6,20 +6,21 @@ import java.math.BigDecimal
 class MapDataContainerTest : DataContainerContract<MapDataContainerTest.SubMap>() {
 
     class SubMap(propertySet: Map<String, Any?>) : MapDataContainer(propertySet), SubClassFields {
-        override var stringField by field<String>()
-        override var noSuchField by field<String>()
+        override var stringField by required<String>()
+        override var noSuchField by required<String>()
     }
 
     class MapBacked(map: Map<String, Any?>) : MapDataContainer(map), MainClassFields<SubMap> {
-        override var stringField by field<String>()
-        override var booleanField by field<Boolean>()
-        override var intField by field<Int>()
-        override var longField by field<Long>()
-        override var doubleField by field<Double>()
-        override var decimalField by field<BigDecimal>()
-        override var notAStringField by field<String>()
+        override var stringField by required<String>()
+        override var booleanField by required<Boolean>()
+        override var intField by required<Int>()
+        override var longField by required<Long>()
+        override var doubleField by required<Double>()
+        override var decimalField by required<BigDecimal>()
+        override var notAStringField by required<String>()
 
-        override var mappedField by field(String::toInt, Int::toString)
+        override var mappedField by required(String::toInt, Int::toString)
+        override var optionalMappedField by optional(String::toInt, Int::toString)
 
         override var listField by list<String>()
         override var listValueField by list(MyType)
@@ -29,12 +30,12 @@ class MapDataContainerTest : DataContainerContract<MapDataContainerTest.SubMap>(
 
         override var objectField by obj(::SubMap)
 
-        override var valueField by field(MyType)
+        override var valueField by required(MyType)
 
-        override var optionalField by field<String?>()
+        override var optionalField by optional<String>()
         override val optionalListField: List<String>? by list()
-        override var optionalObjectField by obj<SubMap?>(::SubMap)
-        override val optionalValueField: MyType? by field(MyType)
+        override var optionalObjectField by optionalObj(::SubMap)
+        override var optionalValueField by optional(MyType)
     }
 
     override fun container(input: Map<String, Any?>) = MapBacked(input)