diff --git a/20200713191259-slaa.org b/20200713191259-slaa.org
index 4b9327c..1b85ae6 100644
--- a/20200713191259-slaa.org
+++ b/20200713191259-slaa.org
@@ -136,3 +136,4 @@ could comprehend what it means to have dignity of self.
 
 * Resources
 - [[https://slaafws.org/][Fellowship-Wide Services]]
+- [[https://slaadvi.org/][S.L.A.A. Greater Delaware Valley Intergroup]]
diff --git a/20210225144943-openapi_core_exceptions.org b/20210225144943-openapi_core_exceptions.org
new file mode 100644
index 0000000..75a9477
--- /dev/null
+++ b/20210225144943-openapi_core_exceptions.org
@@ -0,0 +1,24 @@
+#+title: OpenAPI Core Exceptions
+
+Diagram of the exceptions in the [[file:20210226114112-openapi_core.org][OpenAPI Core]] library.
+
+#+begin_src dot :file openapi-core-exceptions.svg
+  digraph {
+          # openapi-core/openapi_core/casting/schemas/exceptions.py
+          OpenAPIError -> CastError
+          # openapi-core/openapi_core/deserializing/exceptions.py 
+          OpenAPIError -> DeserializeError
+          # openapi-core/openapi_core/deserializing/parameters/exceptions.py
+          DeserializeError -> EmptyParameterValue
+          # openapi-core/openapi_core/unmarshalling/schemas/exceptions.py 
+          OpenAPIError -> UnmarshalError
+          UnmarshalError -> ValidateError
+          UnmarshalError -> UnmarshallerError
+          ValidateError -> InvalidSchemaValue
+          UnmarshallerError -> InvalidSchemaFormatValue
+          UnmarshallerError -> FormatterNotFoundError
+  }
+#+end_src
+
+#+RESULTS:
+[[file:openapi-core-exceptions.svg]]
diff --git a/20210226111129-validating_data_against_a_schema_object.org b/20210226111129-validating_data_against_a_schema_object.org
new file mode 100644
index 0000000..35c905b
--- /dev/null
+++ b/20210226111129-validating_data_against_a_schema_object.org
@@ -0,0 +1,74 @@
+#+title: Validating data against a schema object
+#+roam_tags: openapi-core
+
+How to use [[file:20210226114112-openapi_core.org][OpenAPI Core]]
+
+#+begin_src python :results code :exports both
+  from openapi_core import create_spec
+  from openapi_core.unmarshalling.schemas.factories import SchemaUnmarshallersFactory
+
+  spec = create_spec({
+      "openapi": "3.0.0",
+      "info": {
+          "title": "Test API",
+          "version": "1.0.0",
+      },
+      "components": {
+          "schemas": {
+              "resource": {
+                  "type": "object",
+                  "properties": {"name": {"type": "string"}},
+                  "required": ["name"],
+              },
+          },
+          "securitySchemes": {
+              "basicAuth": {
+                  "type": "http",
+                  "scheme": "bearer",
+              }
+          },
+      },
+      "security": [{"basicAuth": []}],
+      "paths": {
+          "/resource": {
+              "post": {
+                  "requestBody": {
+                      "required": True,
+                      "content": {
+                          "application/vnd.example.resource+json": {
+                              "schema": {"$ref": "#/components/schemas/resource"},
+                          }
+                      },
+                  },
+                  "responses": {
+                      "200": {
+                          "description": "Success",
+                          "content": {
+                              "application/vnd.example.resource+json": {
+                                  "schema": {"$ref": "#/components/schemas/resource"},
+                              }
+                          },
+                      }
+                  },
+              }
+          }
+      },
+  })
+
+  data = {
+      "badname": "Name",
+  }
+
+  factory = SchemaUnmarshallersFactory()
+  unmarshaller = factory.create(spec.components.schemas.get("resource"))
+
+  try:
+      return unmarshaller(data)
+  except Exception as e:
+      return str(e)
+#+end_src
+
+#+RESULTS:
+#+begin_src python
+Value {'badname': 'Name'} not valid for schema of type SchemaType.OBJECT: (<ValidationError: "'name' is a required property">,)
+#+end_src
diff --git a/20210226114112-openapi_core.org b/20210226114112-openapi_core.org
new file mode 100644
index 0000000..674232b
--- /dev/null
+++ b/20210226114112-openapi_core.org
@@ -0,0 +1,4 @@
+#+title: OpenAPI Core
+
+A Python library for validating requests and responses against OpenAPI 3
+specifications.
diff --git a/index.org b/index.org
index 32e5eb6..0b17ddb 100644
--- a/index.org
+++ b/index.org
@@ -8,3 +8,4 @@ A collection of entry points to various interests and ideas.
 - [[file:20210219114633-digital_audio_processing.org][Digital Audio Processing]]
 - [[file:20200716214603-taking_better_notes.org][Taking better notes]]
 - [[file:20200721011317-the_phoenix_inquisitor.org][The Phoenix Inquisitor]]
+- [[file:20210226114112-openapi_core.org][OpenAPI Core]]