diff --git a/backend/deps.edn b/backend/deps.edn
index afc2773f5..422baadde 100644
--- a/backend/deps.edn
+++ b/backend/deps.edn
@@ -44,7 +44,7 @@
 
   mount/mount {:mvn/version "0.1.16"}
   environ/environ {:mvn/version "1.1.0"}}
- :paths ["src" "vendor" "resources"]
+ :paths ["src" "vendor" "resources" "../common"]
  :aliases
  {:dev
   {:extra-deps
diff --git a/backend/src/uxbox/images.clj b/backend/src/uxbox/images.clj
index 1b4137e35..6b2c7633a 100644
--- a/backend/src/uxbox/images.clj
+++ b/backend/src/uxbox/images.clj
@@ -43,8 +43,8 @@
                 width 200
                 height 200}
            :as opts}]
-   {:pre [(us/valid? ::thumbnail-opts opts)
-          (fs/path? input)]}
+   (s/assert ::thumbnail-opts opts)
+   (s/assert fs/path? input)
    (let [tmp (fs/create-tempfile :suffix (str "." format))
          opr (doto (IMOperation.)
                (.addImage)
@@ -60,9 +60,7 @@
 
 (defn make-thumbnail
   [input {:keys [width height format quality] :as opts}]
-  {:pre [(us/valid? ::thumbnail-opts opts)
-         (or (string? input)
-             (fs/path input))]}
+  (s/assert ::thumbnail-opts opts)
   (let [[filename ext] (fs/split-ext (fs/name input))
         suffix (->> [width height quality format]
                     (interpose ".")
diff --git a/backend/src/uxbox/media_loader.clj b/backend/src/uxbox/media_loader.clj
index c49eef0e6..aea849529 100644
--- a/backend/src/uxbox/media_loader.clj
+++ b/backend/src/uxbox/media_loader.clj
@@ -40,7 +40,7 @@
 
 (s/def ::name ::us/string)
 (s/def ::path ::us/string)
-(s/def ::regex us/regex?)
+(s/def ::regex #(instance? java.util.regex.Pattern %))
 (s/def ::import-item
   (s/keys :req-un [::name ::path ::regex]))
 
diff --git a/backend/src/uxbox/services/mutations/project_pages.clj b/backend/src/uxbox/services/mutations/project_pages.clj
index 579b53855..820815ae0 100644
--- a/backend/src/uxbox/services/mutations/project_pages.clj
+++ b/backend/src/uxbox/services/mutations/project_pages.clj
@@ -13,22 +13,22 @@
    [uxbox.services.mutations.project-files :as files]
    [uxbox.services.queries.project-pages :refer [decode-row]]
    [uxbox.services.util :as su]
+   [uxbox.common.pages :as cp]
+   [uxbox.common.spec :as cs]
+   [uxbox.util.exceptions :as ex]
    [uxbox.util.blob :as blob]
-   [uxbox.util.spec :as us]
    [uxbox.util.sql :as sql]
    [uxbox.util.uuid :as uuid]))
 
 ;; --- Helpers & Specs
 
-;; TODO: validate `:data` and `:metadata`
-
-(s/def ::id ::us/uuid)
-(s/def ::name ::us/string)
-(s/def ::data any?)
-(s/def ::user ::us/uuid)
-(s/def ::project-id ::us/uuid)
-(s/def ::metadata any?)
-(s/def ::ordering ::us/number)
+(s/def ::id ::cs/uuid)
+(s/def ::name ::cs/string)
+(s/def ::data ::cp/data)
+(s/def ::user ::cs/uuid)
+(s/def ::project-id ::cs/uuid)
+(s/def ::metadata ::cp/metadata)
+(s/def ::ordering ::cs/number)
 
 ;; --- Mutation: Create Page
 
diff --git a/backend/src/uxbox/util/blob.clj b/backend/src/uxbox/util/blob.clj
index f79e11cdb..6d467fdb9 100644
--- a/backend/src/uxbox/util/blob.clj
+++ b/backend/src/uxbox/util/blob.clj
@@ -26,9 +26,6 @@
   Buffer
   (->bytes [data] (.getBytes ^Buffer data))
 
-  ;; org.jooq.JSONB
-  ;; (->bytes [data] (->bytes (.toString data)))
-
   String
   (->bytes [data] (.getBytes ^String data "UTF-8")))
 
diff --git a/backend/src/uxbox/util/data.clj b/backend/src/uxbox/util/data.clj
index 88cf1785d..f4e6c1743 100644
--- a/backend/src/uxbox/util/data.clj
+++ b/backend/src/uxbox/util/data.clj
@@ -9,6 +9,8 @@
   (:require [clojure.walk :as walk]
             [cuerdas.core :as str]))
 
+;; TODO: move to uxbox.common.helpers
+
 (defn dissoc-in
   [m [k & ks :as keys]]
   (if ks
diff --git a/backend/src/uxbox/util/exceptions.clj b/backend/src/uxbox/util/exceptions.clj
index b39a9e8ce..c32522f17 100644
--- a/backend/src/uxbox/util/exceptions.clj
+++ b/backend/src/uxbox/util/exceptions.clj
@@ -8,6 +8,8 @@
   "A helpers for work with exceptions."
   (:require [clojure.spec.alpha :as s]))
 
+;; TODO: moved to uxbox.common.exceptions
+
 (s/def ::type keyword?)
 (s/def ::code keyword?)
 (s/def ::mesage string?)
diff --git a/backend/src/uxbox/util/transit.clj b/backend/src/uxbox/util/transit.clj
index a601d6e2c..f97bec799 100644
--- a/backend/src/uxbox/util/transit.clj
+++ b/backend/src/uxbox/util/transit.clj
@@ -65,10 +65,6 @@
      (with-open [input (ByteArrayInputStream. data)]
        (read! (reader input opts)))
 
-     ;; ;; TODO: temporal
-     ;; (instance? org.jooq.JSONB data)
-     ;; (decode (.toString data) opts)
-
      (string? data)
      (decode (.getBytes data "UTF-8") opts)
 
diff --git a/backend/test/user.clj b/backend/test/user.clj
index 7c98b0bb8..b9700ed1f 100644
--- a/backend/test/user.clj
+++ b/backend/test/user.clj
@@ -12,19 +12,17 @@
    [clojure.pprint :refer [pprint]]
    [clojure.test :as test]
    [clojure.java.io :as io]
+   [clojure.repl :refer :all]
    [criterium.core :refer [quick-bench bench with-progress-reporting]]
    [expound.alpha :as expound]
    [promesa.core :as p]
-   [sieppari.core :as sp]
-   [sieppari.context :as spx]
-   [buddy.core.codecs :as codecs]
-   [buddy.core.codecs.base64 :as b64]
-   [buddy.core.nonce :as nonce]
+   ;; [sieppari.core :as sp]
+   ;; [sieppari.context :as spx]
+   ;; [buddy.core.codecs :as codecs]
+   ;; [buddy.core.codecs.base64 :as b64]
+   ;; [buddy.core.nonce :as nonce]
    [mount.core :as mount]
-   [uxbox.main]
-   [uxbox.util.sql :as sql]
-   [uxbox.util.blob :as blob])
-  (:gen-class))
+   [uxbox.main]))
 
 (defmacro run-quick-bench
   [& exprs]
@@ -51,11 +49,11 @@
 
 ;; --- Development Stuff
 
-(defn- make-secret
-  []
-  (-> (nonce/random-bytes 64)
-      (b64/encode true)
-      (codecs/bytes->str)))
+;; (defn- make-secret
+;;   []
+;;   (-> (nonce/random-bytes 64)
+;;       (b64/encode true)
+;;       (codecs/bytes->str)))
 
 (defn- start
   []
diff --git a/common/uxbox/common/exceptions.cljc b/common/uxbox/common/exceptions.cljc
new file mode 100644
index 000000000..17c7cf3b8
--- /dev/null
+++ b/common/uxbox/common/exceptions.cljc
@@ -0,0 +1,32 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) 2016-2019 Andrey Antukh <niwi@niwi.nz>
+
+(ns uxbox.util.exceptions
+  "A helpers for work with exceptions."
+  (:require [clojure.spec.alpha :as s]))
+
+(s/def ::type keyword?)
+(s/def ::code keyword?)
+(s/def ::mesage string?)
+(s/def ::hint string?)
+
+(s/def ::error
+  (s/keys :req-un [::type]
+          :opt-un [::code
+                   ::hint
+                   ::mesage]))
+
+(defn error
+  [& {:keys [type code message hint cause] :as params}]
+  (s/assert ::error params)
+  (let [message (or message hint "")
+        payload (dissoc params :cause :message)]
+    (ex-info message payload cause)))
+
+#?(:clj
+   (defmacro raise
+     [& args]
+     `(throw (error ~@args))))
diff --git a/common/uxbox/common/pages.cljc b/common/uxbox/common/pages.cljc
new file mode 100644
index 000000000..3eee32b88
--- /dev/null
+++ b/common/uxbox/common/pages.cljc
@@ -0,0 +1,96 @@
+(ns uxbox.common.pages
+  "A common (clj/cljs) functions and specs for pages."
+  (:require
+   [clojure.spec.alpha :as s]
+   [uxbox.common.spec :as cs]))
+
+;; --- Specs
+
+(s/def ::id ::cs/uuid)
+(s/def ::name string?)
+(s/def ::type keyword?)
+
+;; Metadata related
+(s/def ::grid-x-axis ::cs/number)
+(s/def ::grid-y-axis ::cs/number)
+(s/def ::grid-color string?)
+(s/def ::background string?)
+(s/def ::background-opacity ::cs/number)
+
+;; Page related
+(s/def ::file-id ::cs/uuid)
+(s/def ::user ::cs/uuid)
+(s/def ::created-at ::cs/inst)
+(s/def ::modified-at ::cs/inst)
+(s/def ::version ::cs/number)
+(s/def ::ordering ::cs/number)
+
+;; Page Data related
+(s/def ::shape
+  (s/keys :req-un [::type ::name]
+          :opt-un [::id]))
+
+(s/def ::shapes (s/coll-of ::cs/uuid :kind vector?))
+(s/def ::canvas (s/coll-of ::cs/uuid :kind vector?))
+
+(s/def ::shapes-by-id
+  (s/map-of uuid? ::shape))
+
+;; Main
+
+(s/def ::data
+  (s/keys :req-un [::shapes ::canvas ::shapes-by-id]))
+
+
+(s/def ::metadata
+  (s/keys :opt-un [::grid-y-axis
+                   ::grid-x-axis
+                   ::grid-color
+                   ::background
+                   ::background-opacity]))
+
+(s/def ::opeation
+  (s/or :mod-shape (s/cat :name #(= % :mod-shape)
+                          :id uuid?
+                          :attr keyword?
+                          :value any?)
+        :add-shape (s/cat :name #(= % :add-shape)
+                          :id uuid?
+                          :data any?)
+        :del-shape (s/cat :name #(= % :del-shape)
+                          :id uuid?)))
+
+;; --- Operations Processing Impl
+
+(declare process-operation)
+(declare process-add-shape)
+(declare process-mod-shape)
+(declare process-del-shape)
+
+(defn process-ops
+  [data operations]
+  (reduce process-operation data operations))
+
+(defn- process-operation
+  [data operation]
+  (case (first operation)
+    :add-shape (process-add-shape data operation)
+    :mod-shape (process-mod-shape data operation)
+    :del-shape (process-del-shape data operation)))
+
+(defn- process-add-shape
+  [data {:keys [id data]}]
+  (-> data
+      (update :shapes conj id)
+      (update :shapes-by-id assoc id data)))
+
+(defn- process-mod-shape
+  [data {:keys [id attr value]}]
+  (update-in data [:shapes-by-id id] assoc attr value))
+
+(defn- process-del-shape
+  [data {:keys [id attr value]}]
+  (-> data
+      (update :shapes (fn [s] (filterv #(not= % id) s)))
+      (update :shapes-by-id dissoc id)))
+
diff --git a/common/uxbox/common/spec.cljc b/common/uxbox/common/spec.cljc
new file mode 100644
index 000000000..84dab7391
--- /dev/null
+++ b/common/uxbox/common/spec.cljc
@@ -0,0 +1,120 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) 2016-2019 Andrey Antukh <niwi@niwi.nz>
+
+(ns uxbox.common.spec
+  (:require
+   [clojure.spec.alpha :as s]
+   [cuerdas.core :as str]
+   #?(:clj [datoteka.core :as fs])))
+
+(s/check-asserts true)
+
+;; --- Constants
+
+(def email-rx
+  #"^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$")
+
+(def uuid-rx
+  #"^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$")
+
+(def number-rx
+  #"^[+-]?([0-9]*\.?[0-9]+|[0-9]+\.?[0-9]*)([eE][+-]?[0-9]+)?$")
+
+;; --- Predicates
+
+(defn email?
+  [v]
+  (and (string? v)
+       (re-matches email-rx v)))
+
+;; --- Conformers
+
+(defn- uuid-conformer
+  [v]
+  (cond
+    (uuid? v) v
+    (string? v)
+    (cond
+      (re-matches uuid-rx v)
+      #?(:clj (java.util.UUID/fromString v)
+         :cljs (uuid v))
+
+      (str/empty? v)
+      nil
+
+      :else
+      ::s/invalid)
+    :else ::s/invalid))
+
+(defn- integer-conformer
+  [v]
+  (cond
+    (integer? v) v
+    (string? v)
+    (if (re-matches #"^[-+]?\d+$" v)
+      (Long/parseLong v)
+      ::s/invalid)
+    :else ::s/invalid))
+
+(defn boolean-conformer
+  [v]
+  (cond
+    (boolean? v) v
+    (string? v)
+    (if (re-matches #"^(?:t|true|false|f|0|1)$" v)
+      (contains? #{"t" "true" "1"} v)
+      ::s/invalid)
+    :else ::s/invalid))
+
+(defn boolean-unformer
+  [v]
+  (if v "true" "false"))
+
+#?(:clj
+   (defn path-conformer
+     [v]
+     (cond
+       (string? v) (fs/path v)
+       (fs/path? v) v
+       :else ::s/invalid)))
+
+(defn- number-conformer
+  [v]
+  (cond
+    (number? v) v
+
+    (str/numeric? v)
+    #?(:clj (Double/parseDouble v)
+       :cljs (js/parseFloat v))
+
+    :else ::s/invalid))
+
+;; --- Default Specs
+
+(s/def ::string string?)
+(s/def ::integer (s/conformer integer-conformer str))
+(s/def ::uuid (s/conformer uuid-conformer str))
+(s/def ::boolean (s/conformer boolean-conformer boolean-unformer))
+(s/def ::number (s/conformer number-conformer str))
+
+(s/def ::inst inst?)
+(s/def ::positive pos?)
+(s/def ::negative neg?)
+(s/def ::uploaded-file any?)
+(s/def ::email email?)
+(s/def ::file any?)
+
+;; Clojure Specific
+#?(:clj
+   (do
+     (s/def ::bytes bytes?)
+     (s/def ::name ::string)
+     (s/def ::size ::integer)
+     (s/def ::mtype ::string)
+     (s/def ::path (s/conformer path-conformer str))
+     (s/def ::upload
+       (s/keys :req-un [::name ::path ::size ::mtype]))))
+
diff --git a/frontend/src/uxbox/main/data/pages.cljs b/frontend/src/uxbox/main/data/pages.cljs
index 179724fdb..ab7a7de7e 100644
--- a/frontend/src/uxbox/main/data/pages.cljs
+++ b/frontend/src/uxbox/main/data/pages.cljs
@@ -30,12 +30,14 @@
 (s/def ::version ::us/number)
 (s/def ::width (s/and ::us/number ::us/positive))
 (s/def ::height (s/and ::us/number ::us/positive))
+
 (s/def ::grid-x-axis ::us/number)
 (s/def ::grid-y-axis ::us/number)
 (s/def ::grid-color ::us/string)
-(s/def ::ordering ::us/number)
 (s/def ::background ::us/string)
 (s/def ::background-opacity ::us/number)
+
+(s/def ::ordering ::us/number)
 (s/def ::user ::us/uuid)
 
 (s/def ::metadata
@@ -45,12 +47,14 @@
                    ::background
                    ::background-opacity]))
 
+;; TODO: start using uxbox.common.pagedata/data spec ...
+
 (s/def ::minimal-shape
   (s/keys :req-un [::type ::name]
           :opt-un [::id]))
 
-(s/def ::shapes (s/every ::us/uuid :kind vector? :into []))
-(s/def ::canvas (s/every ::us/uuid :kind vector? :into []))
+(s/def ::shapes (s/coll-of ::us/uuid :kind vector?))
+(s/def ::canvas (s/coll-of ::us/uuid :kind vector?))
 
 (s/def ::shapes-by-id
   (s/map-of ::us/uuid ::minimal-shape))
diff --git a/frontend/src/uxbox/util/data.cljs b/frontend/src/uxbox/util/data.cljs
index 1fd43f8da..f26dcf61e 100644
--- a/frontend/src/uxbox/util/data.cljs
+++ b/frontend/src/uxbox/util/data.cljs
@@ -9,6 +9,8 @@
   (:require [cljs.reader :as r]
             [cuerdas.core :as str]))
 
+;; TODO: partially move to uxbox.common.helpers
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Data structure manipulation
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;