diff --git a/wsme/protocols/commons.py b/wsme/protocols/commons.py
new file mode 100644
index 0000000..08ab746
--- /dev/null
+++ b/wsme/protocols/commons.py
@@ -0,0 +1,76 @@
+import datetime
+import re
+
+from simplegeneric import generic
+
+from wsme.types import iscomplex, list_attributes, Unset
+from wsme.utils import parse_isodate, parse_isotime, parse_isodatetime
+
+
+ARRAY_MAX_SIZE = 1000
+
+
+@generic
+def from_param(datatype, value):
+    return datatype(value) if value else None
+
+
+@from_param.when_object(datetime.date)
+def date_from_param(datatype, value):
+    return parse_isodate(value) if value else None
+
+
+@from_param.when_object(datetime.time)
+def time_from_param(datatype, value):
+    return parse_isotime(value) if value else None
+
+
+@from_param.when_object(datetime.datetime)
+def datetime_from_param(datatype, value):
+    return parse_isodatetime(value) if value else None
+
+
+@generic
+def from_params(datatype, params, path):
+    if iscomplex(datatype):
+        objfound = False
+        for key in params:
+            if key.startswith(path + '.'):
+                objfound = True
+                break
+        if objfound:
+            r = datatype()
+            for attrdef in list_attributes(datatype):
+                value = from_params(attrdef.datatype,
+                        params, '%s.%s' % (path, attrdef.key))
+                if value is not Unset:
+                    setattr(r, attrdef.key, value)
+            return r
+    else:
+        if path in params:
+            return from_param(datatype, params[path])
+    return Unset
+
+
+@from_params.when_type(list)
+def array_from_params(datatype, params, path):
+    if path in params:
+        return [
+            from_param(datatype[0], value) for value in params.getall(path)]
+    else:
+        indexes = set()
+        r = re.compile('^%s\[(?P<index>\d+)\]' % path)
+
+        for p in params.keys():
+            m = r.match(p)
+            if m:
+                indexes.add(int(m.group('index')))
+
+        if not indexes:
+            return Unset
+
+        indexes = list(indexes)
+        indexes.sort()
+
+        return [from_params(datatype[0], params, '%s[%s]' % (path, index))
+                for index in indexes]
diff --git a/wsme/protocols/rest.py b/wsme/protocols/rest.py
index d70f940..fda7f29 100644
--- a/wsme/protocols/rest.py
+++ b/wsme/protocols/rest.py
@@ -1,7 +1,9 @@
 import logging
 
-from wsme.exc import UnknownFunction, MissingArgument, UnknownArgument
+from wsme.exc import ClientSideError, UnknownArgument
 from wsme.protocols import CallContext
+from wsme.protocols.commons import from_params
+from wsme.types import Unset
 
 log = logging.getLogger(__name__)
 
@@ -42,9 +44,13 @@ class RestProtocol(object):
             body = request.params['body']
 
         if body is None and len(request.params):
-            parsed_args = {}
-            for key, value in request.params.items():
-                parsed_args[key] = self.parse_arg(key, value)
+            kw = {}
+            for argdef in funcdef.arguments:
+                value = from_params(
+                    argdef.datatype, request.params, argdef.name)
+                if value is not Unset:
+                    kw[argdef.name] = value
+            return kw
         else:
             if body is None:
                 body = request.body