diff --git a/schema/workflow.yaml b/schema/workflow.yaml
index d98321f3..6d6cd0db 100644
--- a/schema/workflow.yaml
+++ b/schema/workflow.yaml
@@ -302,8 +302,7 @@ $defs:
                 type: string
                 description: The event's unique identifier
               source:
-                type: string
-                format: uri
+                $ref: '#/$defs/uri'
                 description: Identifies the context in which an event happened
               type:
                 type: string
@@ -317,8 +316,7 @@ $defs:
                 type: string
                 description: Content type of data value. This attribute enables data to carry any type of content, whereby format and encoding might differ from that of the chosen event format.
               dataschema:
-                type: string
-                format: uri
+                $ref: '#/$defs/uri'
             required: [ source, type ]
             additionalProperties: true
         required: [ event ]
@@ -567,8 +565,7 @@ $defs:
           type: object
           properties:
             authority:
-              type: string
-              format: uri
+              $ref: '#/$defs/uri'
               description: The URI that references the OAuth2 authority to use.
             grant:
               type: string
@@ -643,15 +640,14 @@ $defs:
     type: object
     properties:
       type:
-        type: string
-        format: uri
+        $ref: '#/$defs/uri'
         description: A URI reference that identifies the error type.
       status:
         type: integer
         description: The status code generated by the origin for this occurrence of the error.
       instance:
         type: string
-        format: uri
+        format: json-pointer
         description: A JSON Pointer used to reference the component the error originates from.
       title:
         type: string
@@ -664,8 +660,7 @@ $defs:
     type: object
     properties:
       uri:
-        type: string
-        format: uri
+        $ref: '#/$defs/uri'
         description: The endpoint's URI.
       authentication:
         $ref: '#/$defs/authenticationPolicy'
@@ -757,8 +752,7 @@ $defs:
     type: object
     properties:
       uri:
-        type: string
-        format: uri
+        $ref: '#/$defs/uri'
         description: The endpoint's URI.
       authentication:
         $ref: '#/$defs/authenticationPolicy'
@@ -875,4 +869,12 @@ $defs:
         description: The duration after which to timeout.
     required: [ after ]
     description: The definition of a timeout.
+  uri:
+    oneOf:
+      - type: string
+        format: uri
+      - type: string
+        # taken from [RFC3986](https://tools.ietf.org/html/rfc3986#appendix-B)
+        pattern: ^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?$
+        
 required: [ document, do ]
\ No newline at end of file