diff --git a/jsonschema/definitions/Catalog.json b/jsonschema/definitions/Catalog.json
index 9b58d1f..fab721e 100644
--- a/jsonschema/definitions/Catalog.json
+++ b/jsonschema/definitions/Catalog.json
@@ -85,13 +85,16 @@
         "keyword": {
             "$id": "http://www.w3.org/ns/dcat#keyword",
             "title": "keyword/tag",
-            "description": "A keyword or tag describing the resource.",
+            "description": "A list of keywords or tags describing the resource.",
             "oneOf": [
                 {
                     "type": "null"
                 },
                 {
-                    "type": "string"
+                    "type": "array",
+                    "items": {
+                        "type": "string"
+                    }
                 }
             ]
         },
@@ -283,7 +286,10 @@
             "$id": "http://purl.org/dc/terms/description",
             "title": "description",
             "description": "Free-text description of the catalog (in the language indicated in the attribute).",
-            "type": "string"
+            "type": [
+                "null", 
+                "string"
+            ]
         },
         "descriptionMap": {
             "$id": "http://purl.org/dc/terms/description_lang_map",
@@ -442,6 +448,9 @@
             "title": "publisher",
             "description": "Entity responsible for making the catalog available.",
             "oneOf": [
+                {
+                    "type": "null"
+                },
                 {
                     "$ref": "#/definitions/Agent",
                     "description": "inline description of Agent"
@@ -584,7 +593,10 @@
             "$id": "http://purl.org/dc/terms/title",
             "title": "title",
             "description": "The title of the catalog in the indicated language",
-            "type": "string"
+            "type": [
+                "null", 
+                "string"
+            ]
         },
         "titleMap": {
             "$id": "http://purl.org/dc/terms/title_lang_map",
@@ -668,9 +680,6 @@
         }
     },
     "required": [
-        "dataset",
-        "description",
-        "publisher",
-        "title"
+        "dataset"
     ]
 }
\ No newline at end of file