diff --git a/web/app/cad/craft/boolean/booleanOpSchema.js b/web/app/cad/craft/boolean/booleanOpSchema.js
index fb309ac1..b2ae15b6 100644
--- a/web/app/cad/craft/boolean/booleanOpSchema.js
+++ b/web/app/cad/craft/boolean/booleanOpSchema.js
@@ -2,11 +2,11 @@ export default {
   operandA: {
     type: 'shell',
     markColor: 0xC9FFBC,
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   operandB: {
     type: 'shell',
     markColor: 0xFFBEB4,
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 1
   }
 };
diff --git a/web/app/cad/craft/cutExtrude/schema.js b/web/app/cad/craft/cutExtrude/schema.js
index 5d680392..a1d77fd3 100644
--- a/web/app/cad/craft/cutExtrude/schema.js
+++ b/web/app/cad/craft/cutExtrude/schema.js
@@ -18,7 +18,7 @@ export default {
   },
   face: {
     type: 'face',
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   datumAxisVector: {
     type: 'datumAxis',
diff --git a/web/app/cad/craft/datum/create/createDatumOpSchema.js b/web/app/cad/craft/datum/create/createDatumOpSchema.js
index fc740e09..2675626e 100644
--- a/web/app/cad/craft/datum/create/createDatumOpSchema.js
+++ b/web/app/cad/craft/datum/create/createDatumOpSchema.js
@@ -1,7 +1,7 @@
 export default {
   originatingFace: {
     type: 'face',
-    defaultValue: {type: 'selection'},
+    initializeBySelection: 0,
     optional: true
   },
   x: {
diff --git a/web/app/cad/craft/datum/move/moveDatumOpSchema.js b/web/app/cad/craft/datum/move/moveDatumOpSchema.js
index 87205ddd..2761e632 100644
--- a/web/app/cad/craft/datum/move/moveDatumOpSchema.js
+++ b/web/app/cad/craft/datum/move/moveDatumOpSchema.js
@@ -1,7 +1,7 @@
 export default {
   datum: {
     type: 'datum',
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   x: {
     type: 'number',
diff --git a/web/app/cad/craft/datum/rotate/rotateDatumOpSchema.js b/web/app/cad/craft/datum/rotate/rotateDatumOpSchema.js
index ed531811..a0ccdc16 100644
--- a/web/app/cad/craft/datum/rotate/rotateDatumOpSchema.js
+++ b/web/app/cad/craft/datum/rotate/rotateDatumOpSchema.js
@@ -1,7 +1,7 @@
 export default {
   datum: {
     type: 'datum',
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   axis: {
     type: 'enum',
diff --git a/web/app/cad/craft/fillet/schema.js b/web/app/cad/craft/fillet/schema.js
index bac6f420..026517ef 100644
--- a/web/app/cad/craft/fillet/schema.js
+++ b/web/app/cad/craft/fillet/schema.js
@@ -2,9 +2,7 @@ export default {
   edges: {
     type: 'array',
     itemType: 'edge',
-    defaultValue: {
-      type: 'selection',
-    }
+    initializeBySelection: true
   },
   thickness: {
     type: 'number',
diff --git a/web/app/cad/craft/intializeBySchema.js b/web/app/cad/craft/intializeBySchema.js
index c00eb9cd..f6610d83 100644
--- a/web/app/cad/craft/intializeBySchema.js
+++ b/web/app/cad/craft/intializeBySchema.js
@@ -9,21 +9,19 @@ export default function initializeBySchema(schema, context) {
     if (md.type === 'array') {
       if (md.itemType === 'object') {
         if (md.defaultValue) {
-          if (md.defaultValue.type === 'selection') {
-            let {itemField, entity} = md.defaultValue;
-            val = context.streams.selection[entity].value.map(s => {
-              let item = initializeBySchema(md.schema, context);
-              item[itemField] = s;
-              return item;
-            });
-          } else {
-            val = md.defaultValue;
-          }
+          val = md.defaultValue;
+        } else if (md.initializeBySelection === true) {
+          let {itemField, entity} = md.defaultValue;
+          val = context.streams.selection[entity].value.map(s => {
+            let item = initializeBySchema(md.schema, context);
+            item[itemField] = s;
+            return item;
+          });
         } else {
           val = [];
         }
       } else if (isEntityType(md.itemType)) {
-        if (md.defaultValue && md.defaultValue.type === 'selection') {
+        if (md.initializeBySelection === true) {
           let entityContext = context.streams.selection[md.itemType];
           if (entityContext) {
             val = [...entityContext.value];
@@ -32,17 +30,15 @@ export default function initializeBySchema(schema, context) {
           val = []
         }
       } else {
-        throw 'unsupport';
+        throw 'unsupported';
       }
-    } else if (isEntityType(md.type) && md.defaultValue && md.defaultValue.type === 'selection') {
+    } else if (isEntityType(md.type) && md.initializeBySelection !== undefined) {
       const entityContext = context.streams.selection[md.type];
       if (entityContext) {
-        val = entityContext.value[0];
+        val = entityContext.value[md.initializeBySelection];
       }
     } else if (md.type === 'object') {
       val = initializeBySchema(md.schema, context);
-    } else if (md.type === 'number') {
-      val = md.defaultValue;
     } else {
       val = md.defaultValue;
     }
diff --git a/web/app/cad/craft/loft/schema.js b/web/app/cad/craft/loft/schema.js
index b90e170b..e963272a 100644
--- a/web/app/cad/craft/loft/schema.js
+++ b/web/app/cad/craft/loft/schema.js
@@ -2,9 +2,7 @@ export default {
   sections: {
     type: 'array',
     itemType: 'loop',
-    defaultValue: {
-      type: 'selection',
-    }
+    initializeBySelection: true
   },
   boolean: {
     type: 'enum',
diff --git a/web/app/cad/craft/materializeParams.js b/web/app/cad/craft/materializeParams.js
index 7a78960f..064cdfdd 100644
--- a/web/app/cad/craft/materializeParams.js
+++ b/web/app/cad/craft/materializeParams.js
@@ -11,7 +11,7 @@ export default function materializeParams(services, params, schema, result, erro
     }
     let value = params[field];
     if (value === undefined || value === null || value === '') {
-      if (!md.optional && !md.hasOwnProperty('defaultValue')) {
+      if (!md.optional) {
         errors.push({path: [...parentPath, field], message: 'required'});
       }
     } else {
diff --git a/web/app/cad/craft/primitives/box/boxOpSchema.js b/web/app/cad/craft/primitives/box/boxOpSchema.js
index 4803e3da..c2813878 100644
--- a/web/app/cad/craft/primitives/box/boxOpSchema.js
+++ b/web/app/cad/craft/primitives/box/boxOpSchema.js
@@ -4,7 +4,7 @@ export default {
   datum: {
     type: 'datum',
     optional: true,
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   width: {
     type: 'number',
diff --git a/web/app/cad/craft/primitives/cone/coneOpSchema.js b/web/app/cad/craft/primitives/cone/coneOpSchema.js
index cedade85..4c0da17f 100644
--- a/web/app/cad/craft/primitives/cone/coneOpSchema.js
+++ b/web/app/cad/craft/primitives/cone/coneOpSchema.js
@@ -4,7 +4,7 @@ export default {
   datum: {
     type: 'datum',
     optional: true,
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   radius: {
     type: 'number',
diff --git a/web/app/cad/craft/primitives/cylinder/cylinderOpSchema.js b/web/app/cad/craft/primitives/cylinder/cylinderOpSchema.js
index 552d7649..47ad5a65 100644
--- a/web/app/cad/craft/primitives/cylinder/cylinderOpSchema.js
+++ b/web/app/cad/craft/primitives/cylinder/cylinderOpSchema.js
@@ -4,7 +4,7 @@ export default {
   datum: {
     type: 'datum',
     optional: true,
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   radius: {
     type: 'number',
diff --git a/web/app/cad/craft/primitives/plane/planeOpSchema.js b/web/app/cad/craft/primitives/plane/planeOpSchema.js
index 1ea295c3..93df2548 100644
--- a/web/app/cad/craft/primitives/plane/planeOpSchema.js
+++ b/web/app/cad/craft/primitives/plane/planeOpSchema.js
@@ -1,6 +1,6 @@
 export default {
   datum: {
     type: 'datum',
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   }
 }
\ No newline at end of file
diff --git a/web/app/cad/craft/primitives/sphere/sphereOpSchema.js b/web/app/cad/craft/primitives/sphere/sphereOpSchema.js
index e32b8d52..91ed1114 100644
--- a/web/app/cad/craft/primitives/sphere/sphereOpSchema.js
+++ b/web/app/cad/craft/primitives/sphere/sphereOpSchema.js
@@ -4,7 +4,7 @@ export default {
   datum: {
     type: 'datum',
     optional: true,
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   radius: {
     type: 'number',
diff --git a/web/app/cad/craft/primitives/torus/torusOpSchema.js b/web/app/cad/craft/primitives/torus/torusOpSchema.js
index 25f4463f..dcfe6f14 100644
--- a/web/app/cad/craft/primitives/torus/torusOpSchema.js
+++ b/web/app/cad/craft/primitives/torus/torusOpSchema.js
@@ -4,7 +4,7 @@ export default {
   datum: {
     type: 'datum',
     optional: true,
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   radius: {
     type: 'number',
diff --git a/web/app/cad/craft/revolve/schema.js b/web/app/cad/craft/revolve/schema.js
index dbfe9bfd..33721394 100644
--- a/web/app/cad/craft/revolve/schema.js
+++ b/web/app/cad/craft/revolve/schema.js
@@ -5,11 +5,11 @@ export default {
   },
   face: {
     type: 'face',
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   axis: {
     type: 'sketchObject',
-    defaultValue: {type: 'selection'}
+    initializeBySelection: 0
   },
   boolean: {
     type: 'enum',