diff --git a/dataforge-context/src/commonMain/kotlin/hep/dataforge/context/PluginManager.kt b/dataforge-context/src/commonMain/kotlin/hep/dataforge/context/PluginManager.kt
index dd114f79..afac0392 100644
--- a/dataforge-context/src/commonMain/kotlin/hep/dataforge/context/PluginManager.kt
+++ b/dataforge-context/src/commonMain/kotlin/hep/dataforge/context/PluginManager.kt
@@ -62,7 +62,7 @@ class PluginManager(override val context: Context) : ContextAware, Iterable<Plug
      * @return
      */
     @Suppress("UNCHECKED_CAST")
-    operator fun <T : Any> get(type: KClass<T>, tag: PluginTag? = null, recursive: Boolean = true): T? =
+    operator fun <T : Any> get(type: KClass<out T>, tag: PluginTag? = null, recursive: Boolean = true): T? =
         find(recursive) { type.isInstance(it) && (tag == null || tag.matches(it.tag)) } as T?
 
     inline operator fun <reified T : Any> get(tag: PluginTag? = null, recursive: Boolean = true): T? =
diff --git a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt
index 243d40bf..b36b3316 100644
--- a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt
+++ b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt
@@ -15,6 +15,10 @@ class MetaBuilder : AbstractMutableMeta<MetaBuilder>() {
     override fun wrapNode(meta: Meta): MetaBuilder = if (meta is MetaBuilder) meta else meta.builder()
     override fun empty(): MetaBuilder = MetaBuilder()
 
+    infix fun String.put(item: MetaItem<*>?) {
+        set(this, item)
+    }
+
     infix fun String.put(value: Value?) {
         set(this, value)
     }
diff --git a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MutableMetaDelegate.kt b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MutableMetaDelegate.kt
index 5ab6ba0c..3fcdc9da 100644
--- a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MutableMetaDelegate.kt
+++ b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MutableMetaDelegate.kt
@@ -49,9 +49,19 @@ fun <T, R> ReadWriteProperty<Any?, T>.map(reader: (T) -> R, writer: (R) -> T): R
 fun <R> ReadWriteProperty<Any?, MetaItem<*>?>.transform(reader: (MetaItem<*>?) -> R): ReadWriteProperty<Any?, R> =
     map(reader = reader, writer = { MetaItem.of(it) })
 
-fun <R> ReadWriteProperty<Any?, Value?>.transform(reader: (Value?) -> R) =
+fun <R> ReadWriteProperty<Any?, Value?>.transform(reader: (Value?) -> R): ReadWriteDelegateWrapper<Value?, R> =
     map(reader = reader, writer = { Value.of(it) })
 
+/**
+ * A delegate that throws
+ */
+fun <R : Any> ReadWriteProperty<Any?, R?>.notNull(default: () -> R): ReadWriteProperty<Any?, R> {
+    return ReadWriteDelegateWrapper(this,
+        reader = { it ?: default() },
+        writer = { it }
+    )
+}
+
 
 fun <M : MutableMeta<M>> M.item(default: Any? = null, key: Name? = null): MutableMetaDelegate<M> =
     MutableMetaDelegate(this, key, default?.let { MetaItem.of(it) })
diff --git a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/scheme/Scheme.kt b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/scheme/Scheme.kt
index 7ac49de0..78d0a511 100644
--- a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/scheme/Scheme.kt
+++ b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/scheme/Scheme.kt
@@ -59,8 +59,7 @@ open class Scheme() : Configurable, Described, MetaRepr {
 /**
  * A specification for simplified generation of wrappers
  */
-open class SchemeSpec<T : Scheme>(val builder: () -> T) :
-    Specification<T> {
+open class SchemeSpec<T : Scheme>(val builder: () -> T) : Specification<T> {
     override fun wrap(config: Config, defaultProvider: (Name) -> MetaItem<*>?): T {
         return builder().apply {
             this.config = config