diff --git a/documentation/data/readme.md b/documentation/data/readme.md
new file mode 100644
index 0000000..b0727a3
--- /dev/null
+++ b/documentation/data/readme.md
@@ -0,0 +1,9 @@
+# @efforting.tech/data
+
+Data processing modules.
+
+**TODO:** *Explain in more detail what this vague description actually refers to.*
+
+## field-configuration-factories.mjs
+
+Currently there are a few factories defined but we might add more as specific needs arises throughout the library.
diff --git a/source/data/field-configuration-factories.mjs b/source/data/field-configuration-factories.mjs
index 4a05668..d6f0749 100644
--- a/source/data/field-configuration-factories.mjs
+++ b/source/data/field-configuration-factories.mjs
@@ -17,4 +17,12 @@ export function typed_value(coercion_function, default_value, description) {
 
 export function typed_factory(coercion_function, factory_function, description) {
 	return new Field_Configuration(null, coercion_function, factory_function, description);
-}
\ No newline at end of file
+}
+
+export function required(description) {
+	return new Field_Configuration((value) => value !== undefined, null, null, description);
+}
+
+export function typed_required(coercion_function, description) {
+	return new Field_Configuration((value) => value !== undefined, coercion_function, null, description);
+}
diff --git a/source/data/field-configuration.mjs b/source/data/field-configuration.mjs
index 4971bfc..827e1db 100644
--- a/source/data/field-configuration.mjs
+++ b/source/data/field-configuration.mjs
@@ -53,12 +53,12 @@ export class Field_Configuration {
 
 export class Schema {
 
-	constructor(field_schema) {
-		Object.assign(this, { field_schema });
+	constructor(field_schema, name=undefined) {
+		Object.assign(this, { field_schema, name });
 	}
 
 	load(value={}, target=undefined) {
-		const { field_schema } = this;
+		const { field_schema, name } = this;
 
 		for (const [value_name, value_value] of Object.entries(value)) {
 			if (!field_schema[value_name]) {
@@ -69,8 +69,10 @@ export class Schema {
 		}
 
 		const result = {};
+		const this_schema = name ? `schema "${name}"` : 'untitled schema';
+
 		for (const [field_name, field_config] of Object.entries(field_schema)) {
-			const sub_target = { schema: this, field_name, field_config, parent_target: target };
+			const sub_target = { schema: this, name: field_name, config: field_config, parent_target: target, info: `Field "${field_name}" of ${this_schema}` };
 			result[field_name] = field_config.load(value[field_name], sub_target);
 		}
 
diff --git a/source/rule-processing/resolvers.mjs b/source/rule-processing/resolvers.mjs
index 47fe57a..f958458 100644
--- a/source/rule-processing/resolvers.mjs
+++ b/source/rule-processing/resolvers.mjs
@@ -30,6 +30,7 @@ export class Chained_Resolver extends Abstract_Resolver {
 
 export class Mapping_Resolver extends Abstract_Resolver {
 	constructor(rules=new Map(), key_function=null) {
+		super();
 		Object.assign(this, { rules, key_function });
 	}