diff --git a/README.md b/README.md
index 1b10cf9..278a62d 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,7 @@
+---
+WARN: It is just a prototype and currently just a subset of XSD capabilities.
+---
+
 # YASD, Yet Another Schema Definition
 
 YASD is a YAML format for human writable XSDs (XML Schema Definition), humans
@@ -36,7 +40,7 @@ To better understad what YASD does, see the inputs and outputs:
 
 ## Table of Contents
 
-[TOC]
+\[TOC\]
 
 ## Structure
 
@@ -68,7 +72,8 @@ To better understad what YASD does, see the inputs and outputs:
     type: simple|empty|no_text|no_elements|mixed 
     datatype: string|integer|decimal|date|time|language|duration|token|boolean|byte|int|double|float|long|short|normalizedString|dateTime|gDay|gMonth|gMonthDay|gYear|gYearMonth|negativeInteger|nonNegativeInteger|nonPositiveInteger|positiveInteger|unsignedLong|unsignedInt|unsignedShort|unsignedByte|anyURI|base64Binary|hexBinary|Name|QName|NCName|ID|IDREF|IDREFS|ENTITY|ENTITIES|NMTOKEN|NMTOKENS|NOTATION
     attributes:
-      - name: attribute_name
+      - ref: attribute_name
+        use: optional|required|prohibited
       - group: group_name
       ...
     children_order: all|choice|sequence
@@ -77,6 +82,8 @@ To better understad what YASD does, see the inputs and outputs:
         maxOccurs: INTEGER|unbounded
         minOccurs: INTEGER
       - group_ref: group_name
+        maxOccurs: INTEGER|unbounded
+        minOccurs: INTEGER
       ...
 
 ### Attribute (ATTR) structure
@@ -86,7 +93,6 @@ To better understad what YASD does, see the inputs and outputs:
     datatype: string|integer|decimal|date|time|language|duration|token|boolean|byte|int|double|float|long|short|normalizedString|dateTime|gDay|gMonth|gMonthDay|gYear|gYearMonth|negativeInteger|nonNegativeInteger|nonPositiveInteger|positiveInteger|unsignedLong|unsignedInt|unsignedShort|unsignedByte|anyURI|base64Binary|hexBinary|Name|QName|NCName|ID|IDREF|IDREFS|ENTITY|ENTITIES|NMTOKEN|NMTOKENS|NOTATION
     default: a_value
     fixed: a_value
-    use: required
     restriction:
       - CONSTRAIN
       ...
@@ -188,7 +194,7 @@ Chart:
     | no_elements | ✗        | ✓    | ✓          |
     | mixed       | ✓        | ✓    | ✓          |
 
-> **Note 1**: read "elements" and "text" with "direct children…" as prefix.
+> **Note 1**: read "elements" and "text" with "direct children..." as prefix.
 
 > **Note 2**: attributes are never mandatory; they could be zero or more.
 
@@ -282,15 +288,20 @@ Only allowed for simple elements or attributes.
 
 Indicates that the attribute is required.
 
-Optional.
+Optional; if not present by default is `optional`.
 
-Only `required` is valid as value.
+Allowed uses:
+
+-   `optional`.
+-   `required`.
+-   `prohibited`.
 
 ### `restriction`
 
 Indicates accepted constrained values for attribute.
 
-Optional; if present, must contain at least one constrain.
+Optional; if present, must contain at least one constrain and attribute
+`datatype` is ignored.
 
 Allowed constrains:
 
diff --git a/yasd.py b/yasd.py
index e81bc4b..2e7ce97 100755
--- a/yasd.py
+++ b/yasd.py
@@ -142,6 +142,7 @@ class YASD:
         """
         if type(outdata) is not str:
             outdata = outdata.prettify(formatter=self.formatter)
+            outdata = f'<?xml version="1.0"?>\n{outdata}'
         if self.stdout:
             if self.outfile is None:
                 print(outdata)
@@ -219,6 +220,7 @@ class YASDXSD:
                 ...
             else:
                 element = self.xsd.new_tag("group", nsprefix="xs")
+                element["name"] = el["name"]
                 indicator = self.__build_indicator(el)
                 element.append(indicator)
             self.xsd.schema.append(element)
@@ -233,6 +235,8 @@ class YASDXSD:
         element = self.xsd.new_tag(tag, nsprefix="xs")
         if "default" in el.keys() and "fixed" in el.keys():
             del el["fixed"]
+        if "restriction" in el.keys() and "datatype" in el.keys():
+            del el["datatype"]
         for key, val in el.items():
             if key == "datatype":
                 element["type"] = f"xs:{val}"
@@ -250,10 +254,13 @@ class YASDXSD:
         """
         element = self.__build_complex_root(el)
         complex_type = self.__build_complex_type(el)
-        self.__add_references(complex_type, el, is_attr=True)
         if "children" in el.keys():
-            indicator = self.__build_indicator(el)
-            complex_type.append(indicator)
+            if "group" in el["children"][0].keys():
+                self.__add_references(complex_type, el)
+                self.__add_occurs(complex_type.group, el)
+            else:
+                complex_type.append(self.__build_indicator(el))
+        self.__add_references(complex_type, el, is_attr=True)
         element.append(complex_type)
         self.xsd.schema.append(element)
 
@@ -378,14 +385,25 @@ class YASDXSD:
         if key in el.keys():
             for element in el[key]:
                 node = self.xsd.new_tag(tag, nsprefix="xs")
+                self.__add_occurs(node, element)
                 node["ref"] = element[name]
-                if "maxOccurs" in element.keys():
-                    node["maxOccurs"] = element["maxOccurs"]
-                if "minOccurs" in element.keys():
-                    node["minOccurs"] = element["minOccurs"]
+                if "use" in element.keys():
+                    node["use"] = element["use"]
                 root.append(node)
             del el[key]
 
+    def __add_occurs(self, node, el):
+        """
+        Adds occurrences to node.
+
+        :param bs4.element.Tag node: node that requires occurrences
+        :param dict el: element that indicates if there are occurrences
+        """
+        if "minOccurs" in el.keys():
+            node["minOccurs"] = el["minOccurs"]
+        if "maxOccurs" in el.keys():
+            node["maxOccurs"] = el["maxOccurs"]
+
     def __sanitize(self, el):
         """
         Prepares element or attribute for conversion.