diff --git a/packages/@aws-cdk/cdk-cfnspec/.npmignore b/packages/@aws-cdk/cdk-cfnspec/.npmignore
index ff4a25b8edcc2..bce5cfa662346 100644
--- a/packages/@aws-cdk/cdk-cfnspec/.npmignore
+++ b/packages/@aws-cdk/cdk-cfnspec/.npmignore
@@ -1,3 +1,3 @@
 *.ts
 !*.d.ts
-spec-input
+spec-source
diff --git a/packages/@aws-cdk/cdk-cfnspec/build-tools/build.ts b/packages/@aws-cdk/cdk-cfnspec/build-tools/build.ts
index 78f807da1dbd7..b424974b12b58 100644
--- a/packages/@aws-cdk/cdk-cfnspec/build-tools/build.ts
+++ b/packages/@aws-cdk/cdk-cfnspec/build-tools/build.ts
@@ -1,3 +1,10 @@
+/*
+ * Invoked as part of the "build" script of this package,
+ * this script takes all specification fragments in the
+ * `spec-source` folder and generates a unified specification
+ * document at `spec/specification.json`.
+ */
+
 import { applyPatch } from 'fast-json-patch';
 import * as fs from 'fs-extra';
 import * as md5 from 'md5';
@@ -5,7 +12,7 @@ import * as path from 'path';
 import { schema } from '../lib';
 
 async function main() {
-    const inputDir = path.join(process.cwd(), 'spec-input');
+    const inputDir = path.join(process.cwd(), 'spec-source');
     const files = await fs.readdir(inputDir);
     const spec: schema.Specification = { PropertyTypes: {}, ResourceTypes: {}, Fingerprint: '' };
     for (const file of files.filter(n => n.endsWith('.json')).sort()) {
@@ -99,7 +106,6 @@ function normalize(spec: schema.Specification): schema.Specification {
 }
 
 main()
-    .then(() => process.exit(0))
     .catch(e => {
         // tslint:disable-next-line:no-console
         console.error(e.stack);
diff --git a/packages/@aws-cdk/cdk-cfnspec/build-tools/update.sh b/packages/@aws-cdk/cdk-cfnspec/build-tools/update.sh
index 60cc73ab833c8..8f7c776e78a47 100644
--- a/packages/@aws-cdk/cdk-cfnspec/build-tools/update.sh
+++ b/packages/@aws-cdk/cdk-cfnspec/build-tools/update.sh
@@ -1,5 +1,12 @@
 #!/bin/bash
+
+###
+# Updates the AWS CloudFormation Resource Specification using the files published on the AWS Documentaiton.
+# See: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-resource-specification.html
+###
+
 set -euo pipefail
 
+rm -f spec-source/000_CloudFormationResourceSpecification.json
 curl -L "https://d1uauaxba7bl26.cloudfront.net/latest/gzip/CloudFormationResourceSpecification.json" \
-    | gunzip - > spec-input/000_CloudFormationResourceSpecification.json
+    | gunzip - > spec-source/000_CloudFormationResourceSpecification.json
diff --git a/packages/@aws-cdk/cdk-cfnspec/lib/schema/base-types.ts b/packages/@aws-cdk/cdk-cfnspec/lib/schema/base-types.ts
index 0d213542ba330..505785317e98c 100644
--- a/packages/@aws-cdk/cdk-cfnspec/lib/schema/base-types.ts
+++ b/packages/@aws-cdk/cdk-cfnspec/lib/schema/base-types.ts
@@ -3,17 +3,25 @@ export interface Documented {
     Documentation: string;
 }
 
-export type PrimitiveType = 'String' | 'Long' | 'Integer' | 'Double' | 'Boolean' | 'Timestamp' | 'Json';
+export enum PrimitiveType {
+    String = 'String',
+    Long = 'Long',
+    Integer = 'Integer',
+    Double = 'Double',
+    Boolean = 'Boolean',
+    Timestamp = 'Timestamp',
+    Json = 'Json'
+}
 
 export function isPrimitiveType(str: string): str is PrimitiveType {
     switch (str) {
-    case 'String':
-    case 'Long':
-    case 'Integer':
-    case 'Double':
-    case 'Boolean':
-    case 'Timestamp':
-    case 'Json':
+    case PrimitiveType.String:
+    case PrimitiveType.Long:
+    case PrimitiveType.Integer:
+    case PrimitiveType.Double:
+    case PrimitiveType.Boolean:
+    case PrimitiveType.Timestamp:
+    case PrimitiveType.Json:
         return true;
     default:
         return false;
diff --git a/packages/@aws-cdk/cdk-cfnspec/lib/schema/property.ts b/packages/@aws-cdk/cdk-cfnspec/lib/schema/property.ts
index 52b51be5524ee..a4685738c69a7 100644
--- a/packages/@aws-cdk/cdk-cfnspec/lib/schema/property.ts
+++ b/packages/@aws-cdk/cdk-cfnspec/lib/schema/property.ts
@@ -86,13 +86,17 @@ export interface UnionProperty extends PropertyBase {
     ItemTypes?: string[];
 }
 
-type UpdateType = 'Conditional' | 'Immutable' | 'Mutable';
+export enum UpdateType {
+    Conditional = 'Conditional',
+    Immutable = 'Immutable',
+    Mutable = 'Mutable'
+}
 
 export function isUpdateType(str: string): str is UpdateType {
     switch (str) {
-    case 'Conditional':
-    case 'Immutable':
-    case 'Mutable':
+    case UpdateType.Conditional:
+    case UpdateType.Immutable:
+    case UpdateType.Mutable:
         return true;
     default:
         return false;
diff --git a/packages/@aws-cdk/cdk-cfnspec/spec-input/000_CloudFormationResourceSpecification.json b/packages/@aws-cdk/cdk-cfnspec/spec-source/000_CloudFormationResourceSpecification.json
similarity index 100%
rename from packages/@aws-cdk/cdk-cfnspec/spec-input/000_CloudFormationResourceSpecification.json
rename to packages/@aws-cdk/cdk-cfnspec/spec-source/000_CloudFormationResourceSpecification.json
diff --git a/packages/@aws-cdk/cdk-cfnspec/spec-input/000_sam.spec.json b/packages/@aws-cdk/cdk-cfnspec/spec-source/000_sam.spec.json
similarity index 100%
rename from packages/@aws-cdk/cdk-cfnspec/spec-input/000_sam.spec.json
rename to packages/@aws-cdk/cdk-cfnspec/spec-source/000_sam.spec.json
diff --git a/packages/@aws-cdk/cdk-cfnspec/spec-input/500_Cognity_IdentityPoolRoleAttachment_patches.json b/packages/@aws-cdk/cdk-cfnspec/spec-source/500_Cognity_IdentityPoolRoleAttachment_patches.json
similarity index 100%
rename from packages/@aws-cdk/cdk-cfnspec/spec-input/500_Cognity_IdentityPoolRoleAttachment_patches.json
rename to packages/@aws-cdk/cdk-cfnspec/spec-source/500_Cognity_IdentityPoolRoleAttachment_patches.json
diff --git a/packages/@aws-cdk/cdk-cfnspec/spec-input/500_SAM_Serverless_Function_S3Event_Events_patch.json b/packages/@aws-cdk/cdk-cfnspec/spec-source/500_SAM_Serverless_Function_S3Event_Events_patch.json
similarity index 100%
rename from packages/@aws-cdk/cdk-cfnspec/spec-input/500_SAM_Serverless_Function_S3Event_Events_patch.json
rename to packages/@aws-cdk/cdk-cfnspec/spec-source/500_SAM_Serverless_Function_S3Event_Events_patch.json
diff --git a/packages/@aws-cdk/cdk-cfnspec/spec-input/500_SAM_Serverless_Function_S3Location_Version_patch.json b/packages/@aws-cdk/cdk-cfnspec/spec-source/500_SAM_Serverless_Function_S3Location_Version_patch.json
similarity index 100%
rename from packages/@aws-cdk/cdk-cfnspec/spec-input/500_SAM_Serverless_Function_S3Location_Version_patch.json
rename to packages/@aws-cdk/cdk-cfnspec/spec-source/500_SAM_Serverless_Function_S3Location_Version_patch.json
diff --git a/packages/@aws-cdk/cdk-cfnspec/spec-input/500_SSM_AssociationName_patch.json b/packages/@aws-cdk/cdk-cfnspec/spec-source/500_SSM_AssociationName_patch.json
similarity index 100%
rename from packages/@aws-cdk/cdk-cfnspec/spec-input/500_SSM_AssociationName_patch.json
rename to packages/@aws-cdk/cdk-cfnspec/spec-source/500_SSM_AssociationName_patch.json
diff --git a/packages/@aws-cdk/cdk-cfnspec/spec-input/500_SSM_AssociationName_patch.md b/packages/@aws-cdk/cdk-cfnspec/spec-source/500_SSM_AssociationName_patch.md
similarity index 100%
rename from packages/@aws-cdk/cdk-cfnspec/spec-input/500_SSM_AssociationName_patch.md
rename to packages/@aws-cdk/cdk-cfnspec/spec-source/500_SSM_AssociationName_patch.md
diff --git a/packages/@aws-cdk/cdk-cfnspec/spec-input/510_ElasticSearch_Domain_patches.json b/packages/@aws-cdk/cdk-cfnspec/spec-source/510_ElasticSearch_Domain_patches.json
similarity index 100%
rename from packages/@aws-cdk/cdk-cfnspec/spec-input/510_ElasticSearch_Domain_patches.json
rename to packages/@aws-cdk/cdk-cfnspec/spec-source/510_ElasticSearch_Domain_patches.json
diff --git a/packages/@aws-cdk/cdk-cfnspec/test/spec-validators.ts b/packages/@aws-cdk/cdk-cfnspec/test/spec-validators.ts
index 2b0fac24bb6df..f729f97c18c70 100644
--- a/packages/@aws-cdk/cdk-cfnspec/test/spec-validators.ts
+++ b/packages/@aws-cdk/cdk-cfnspec/test/spec-validators.ts
@@ -3,6 +3,11 @@ import * as schema from '../lib/schema';
 import { Specification } from '../lib/schema';
 
 export function validateSpecification(test: Test, specification: Specification) {
+    validateResourceTypes(test, specification);
+    validatePropertyTypes(test, specification);
+}
+
+function validateResourceTypes(test: Test, specification: Specification) {
     for (const typeName of Object.keys(specification.ResourceTypes)) {
         test.ok(typeName, 'Resource type name is not empty');
         const type = specification.ResourceTypes[typeName];
@@ -10,6 +15,9 @@ export function validateSpecification(test: Test, specification: Specification)
         if (type.Properties) { validateProperties(typeName, test, type.Properties, specification); }
         if (type.Attributes) { validateAttributes(typeName, test, type.Attributes, specification); }
     }
+}
+
+function validatePropertyTypes(test: Test, specification: Specification) {
     for (const typeName of Object.keys(specification.PropertyTypes)) {
         test.ok(typeName, 'Property type name is not empty');
         const type = specification.PropertyTypes[typeName];