diff --git a/models/dimers random walk.xml b/models/dimers random walk.xml
index dd1e7a1..7111d1c 100644
--- a/models/dimers random walk.xml	
+++ b/models/dimers random walk.xml	
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<gem-graph-model version="0.2">
+<gem-graph-model version="0.2.1">
     <identity>
        <name>Modèle de test</name>
 
@@ -26,15 +26,13 @@
     <!-- loop_on_zero="false" anything moved before zero is lost-->
     <!-- loop_on_max="true"   anything moved beyond max reenters at the zero of space-->
     <!-- loop_on_max="false"  anything moved beyond max is lost-->
-    
-            <dimension>
-                <coord axis="x" at="29"/>
-            </dimension>
-            
+
+            <dimension x="29"/>
+
             <!-- Site_multiplicity = number of  sites in a space unit. -->
             <!-- Each site points towards a neighbouring space unit. -->
             <!-- Several arrows can be stacked in the same site. -->
-            
+
             <site_multiplicity>3</site_multiplicity>
 
         </space-param>
@@ -42,27 +40,27 @@
     </parameters>
 
     <!-- Model objects definition -->
-    
+
     <objects id="only dimers in this model" date="1630000000" author="inanimés,... âme ?">
         <object id="a dimer" date="1630000000" author="Alphonse">
-            <arrow site="1" weight="1"><coord axis="x" at="0"/></arrow>
-            <arrow site="2" weight="1"><coord axis="x" at="1"/></arrow>
+            <arrow site="1" weight="1" x="0"/>
+            <arrow site="2" weight="1" x="1"/>
         </object>
 
     </objects>
 
-    
+
     <!-- Saved space description (initial space is sequence 0) -->
-    
+
     <savedstates id="texte" date="1630000000" author="Qui courrait dans l'herbe'">
         <state id="initial" date="1630000000" author="Une souris verte">
-            <arrow site="1" weight="1"><coord axis="x" at="0"/></arrow>
-            <arrow site="2" weight="1"><coord axis="x" at="1"/></arrow>
-            <arrow site="1" weight="1"><coord axis="x" at="10"/></arrow>
-            <arrow site="2" weight="1"><coord axis="x" at="11"/></arrow>
-            <arrow site="1" weight="1"><coord axis="x" at="20"/></arrow>
-            <arrow site="2" weight="1"><coord axis="x" at="21"/></arrow>
-            
+            <arrow site="1" weight="1" x="0"/>
+            <arrow site="2" weight="1" x="1"/>
+            <arrow site="1" weight="1" x="10"/>
+            <arrow site="2" weight="1" x="11"/>
+            <arrow site="1" weight="1" x="20"/>
+            <arrow site="2" weight="1" x="21"/>
+
           <!-- Three dimers 1-1 are drawn in the global space
                at locations (0,1) (10,11) and (20,21) -->
 
@@ -76,16 +74,16 @@
 
     <conditions id="random walk of dimers" date="1630000000" author="Zazard le lézard !">
 
-        <condition site="1" weight="1" node_id="1" parent="0"><coord axis="x" at="0"/></condition>
-        <condition site="2" weight="1" node_id="2" parent="1"><coord axis="x" at="1"/></condition>
+        <condition site="1" weight="1" node_id="1" parent="0" x="0"/>
+        <condition site="2" weight="1" node_id="2" parent="1" x="1"/>
         <!-- as soon as conditions 1 and 2 are satisfied, a dimer is identified at atation (0,1). -->
 
-        <condition site="1" weight="0" node_id="3" parent="2"><coord axis="x" at="2"/></condition>
+        <condition site="1" weight="0" node_id="3" parent="2" x="2"/>
         <!-- as soon as condition 3 is satisfied,
              the neighbouring space unit to East of the dimer is empty
              and the dimer identified by conditions (1,2)  can be moved to East. -->
 
-        <condition site="2" weight="0" node_id="4" parent="2"><coord axis="x" at="-1"/></condition>
+        <condition site="2" weight="0" node_id="4" parent="2" x="-1"/>
         <!-- as soon as condition 4 is satisfied,
              the neighbouring space unit to West of the dimer is empty
              and  the dimer identified by conditions (1,2) can be moved to West. -->
@@ -97,20 +95,20 @@
         <transition id="move_a_dimer_to_east" date="1630000000" author="Pas moi..."
                   parent="3" probability="1">
 
-            <arrow site="1" weight="0"><coord axis="x" at="0"/></arrow>
-            <arrow site="2" weight="0"><coord axis="x" at="1"/></arrow>
-            <arrow site="1" weight="1"><coord axis="x" at="1"/></arrow>
-            <arrow site="2" weight="1"><coord axis="x" at="2"/></arrow>
+            <arrow site="1" weight="0" x="0"/>
+            <arrow site="2" weight="0" x="1"/>
+            <arrow site="1" weight="1" x="1"/>
+            <arrow site="2" weight="1" x="2"/>
 
       </transition>
 
       <transition id="move_a_dimer_to_west" date="1630000000" author="Ni moi !"
                   parent="4" probability="1">
 
-            <arrow site="1" weight="0"><coord axis="x" at="0"/></arrow>
-            <arrow site="2" weight="0"><coord axis="x" at="1"/></arrow>
-            <arrow site="2" weight="1"><coord axis="x" at="0"/></arrow>
-            <arrow site="1" weight="1"><coord axis="x" at="1"/></arrow>
+            <arrow site="1" weight="0" x="0"/>
+            <arrow site="2" weight="0" x="1"/>
+            <arrow site="2" weight="1" x="0"/>
+            <arrow site="1" weight="1" x="1"/>
 
       </transition>
 
diff --git a/models/testing.xml b/models/testing.xml
new file mode 100644
index 0000000..2a30294
--- /dev/null
+++ b/models/testing.xml
@@ -0,0 +1,83 @@
+<gem-graph-model version="0.2">
+	<!-- Model identity informations -->
+	<identity>
+		<name>Modèle de test</name>
+		<owner>Gaston Lagaffe</owner>
+		<owner_id>2</owner_id>
+		<date>1629830000</date>
+		<version>1.0</version>
+		<g_ref id="texte" date="1629830000" author="Jean" lang="en">Ref</g_ref>
+	</identity>
+	<!-- Model parameters -->
+	<parameters id="texte" date="0" author="Gaston Lagaffe">
+		<simulation>
+			<max_thread>0</max_thread>
+			<max_cycles>9</max_cycles>
+		</simulation>
+		<space-param>
+			<dimension>
+				<!-- loop_on_zero="true"  anything moved before zero reenters at the end of space-->
+				<!-- loop_on_zero="false" anything moved before zero is lost-->
+				<!-- loop_on_max="true"   anything moved beyond max reenters at the zero of space-->
+				<!-- loop_on_max="false"  anything moved beyond max is lost-->
+				<axis name="x" size="29"/>
+				<axis name="y" size="0"/>
+				<axis name="z" size="0"/>
+			</dimension>
+			<!-- Site_multiplicity = number of  sites in a space unit. -->
+			<!-- Each site points towards a neighbouring space unit. -->
+			<!-- Several arrows can be stacked in the same site. -->
+			<site_multiplicity>3</site_multiplicity>
+		</space-param>
+	</parameters>
+	<!-- Model objects definition -->
+	<objects id="texte" date="1629830000" author="Jean Sirmai">
+		<object id="dimer 1-1" date="1629830000" author="Jean Sirmai">
+			<arrow x="0" y="0" z="0" site="1" weight="1"/>
+			<arrow x="1" y="0" z="0" site="2" weight="1"/>
+		</object>
+	</objects>
+	<!-- Saved space description (initial space is sequence 0) -->
+	<savestates id="texte" date="1629830000" author="THE MATRIX">
+		<space id="initial" date="1629830000" author="Jean Sirmai" sequence="0">
+			<arrow x="0" y="0" z="0" site="1" weight="1"/>
+			<arrow x="1" y="0" z="0" site="2" weight="1"/>
+			<arrow x="10" y="0" z="0" site="1" weight="1"/>
+			<arrow x="11" y="0" z="0" site="2" weight="1"/>
+			<arrow x="20" y="0" z="0" site="1" weight="1"/>
+			<arrow x="21" y="0" z="0" site="2" weight="1"/>
+			<!-- Three dimers 1-1 are drawn in the global space
+               at locations (0,1) (10,11) and (20,21) -->
+		</space>
+	</savestates>
+	<!-- Model transitions definition (rules) -->
+	<!-- In this version : <xs:sequence minOccurs="0" maxOccurs="unbounded">-->
+	<!-- Transitions should be edited by hand and written in a 'human-readable' format -->
+	<conditions id="random walk of dimers" date="1629822222" author="Jean">
+		<condition x="0" y="0" z="0" site="1" weight="1" node_id="1" parent="0"/>
+		<condition x="1" y="0" z="0" site="2" weight="1" node_id="2" parent="1"/>
+		<!-- as soon as conditions 1 and 2 are satisfied, a dimer is identified at location (0,1). -->
+		<condition x="2" y="0" z="0" site="1" weight="0" node_id="3" parent="2"/>
+		<!-- as soon as condition 3 is satisfied,
+             the neighbouring space unit to East of the dimer is empty
+             and the dimer identified by conditions (1,2)  can be moved to East. -->
+		<condition x="-1" y="0" z="0" site="2" weight="0" node_id="4" parent="2"/>
+		<!-- as soon as condition 4 is satisfied,
+             the neighbouring space unit to West of the dimer is empty
+             and  the dimer identified by conditions (1,2) can be moved to West. -->
+	</conditions>
+	<transitions>
+		<transition id="move_a_dimer_to_east" date="1629811111" author="Jean" parent="3" probability="1">
+			<arrow x="0" y="0" z="0" site="1" weight="0"/>
+			<arrow x="1" y="0" z="0" site="2" weight="0"/>
+			<arrow x="1" y="0" z="0" site="1" weight="1"/>
+			<arrow x="2" y="0" z="0" site="2" weight="1"/>
+		</transition>
+		<transition id="move_a_dimer_to_west" date="1629811112" author="Jean" parent="4" probability="1">
+			<arrow x="0" y="0" z="0" site="1" weight="0"/>
+			<arrow x="1" y="0" z="0" site="2" weight="0"/>
+			<arrow x="0" y="0" z="0" site="2" weight="1"/>
+			<arrow x="-1" y="0" z="0" site="1" weight="1"/>
+		</transition>
+	</transitions>
+</gem-graph-model>
\ No newline at end of file
diff --git a/schemas/models_0.2.xmls b/schemas/models_0.2.1.xmls
similarity index 77%
rename from schemas/models_0.2.xmls
rename to schemas/models_0.2.1.xmls
index f106f88..b58a130 100644
--- a/schemas/models_0.2.xmls
+++ b/schemas/models_0.2.1.xmls
@@ -14,6 +14,13 @@
 <xs:attribute name="probability" type="xs:integer"/>
 <xs:attribute name="site" type="xs:integer" default="0"/>
 <xs:attribute name="weight" type="xs:integer" default="0"/>
+<xs:attribute name="u" type="xs:integer"/>
+<xs:attribute name="v" type="xs:integer"/>
+<xs:attribute name="w" type="xs:integer"/>
+<xs:attribute name="x" type="xs:integer"/>
+<xs:attribute name="y" type="xs:integer"/>
+<xs:attribute name="z" type="xs:integer"/>
+<xs:attribute name="t" type="xs:integer"/>
 
 
 <xs:attributeGroup name="id_date_author">
@@ -35,40 +42,45 @@
 
 <xs:element name="quote" substitutionGroup="g_ref"/>
 
-<xs:element name="coord">
-    <xs:complexType>
-        <xs:attribute name="axis" type="xs:string" use="required"/>
-        <xs:attribute name="at" type="xs:integer" use="required"/>
-    </xs:complexType>
-</xs:element>
-
 <xs:element name="dimension">
     <xs:complexType>
-    <xs:sequence minOccurs="1" maxOccurs="unbounded">
-        <xs:element ref="coord"/>
-    </xs:sequence>
+        <xs:attribute ref="u" use="optional"/>
+        <xs:attribute ref="v" use="optional"/>
+        <xs:attribute ref="w" use="optional"/>
+        <xs:attribute ref="x" use="optional"/>
+        <xs:attribute ref="y" use="optional"/>
+        <xs:attribute ref="z" use="optional"/>
+        <xs:attribute ref="t" use="optional"/>
     </xs:complexType>
 </xs:element>
 
 <xs:element name="arrow">
     <xs:complexType>
-        <xs:sequence minOccurs="1" maxOccurs="unbounded">
-            <xs:element ref="coord"/>
-        </xs:sequence>
-        <xs:attribute name="site" use="required"/>
-        <xs:attribute name="weight" use="required"/>
+        <xs:attribute ref="site" use="required"/>
+        <xs:attribute ref="weight" use="required"/>
+        <xs:attribute ref="u" use="optional"/>
+        <xs:attribute ref="v" use="optional"/>
+        <xs:attribute ref="w" use="optional"/>
+        <xs:attribute ref="x" use="optional"/>
+        <xs:attribute ref="y" use="optional"/>
+        <xs:attribute ref="z" use="optional"/>
+        <xs:attribute ref="t" use="optional"/>
     </xs:complexType>
 </xs:element>
 
 <xs:element name="condition">
     <xs:complexType>
-        <xs:sequence minOccurs="1" maxOccurs="unbounded">
-            <xs:element ref="coord" minOccurs="1" maxOccurs="unbounded"/>
-        </xs:sequence>
-        <xs:attribute name="site" use="required"/>
-        <xs:attribute name="weight" use="required"/>
+        <xs:attribute ref="site" use="required"/>
+        <xs:attribute ref="weight" use="required"/>
         <xs:attribute ref="node_id" use="required"/>
         <xs:attribute ref="parent" use="required"/>
+        <xs:attribute ref="u" use="optional"/>
+        <xs:attribute ref="v" use="optional"/>
+        <xs:attribute ref="w" use="optional"/>
+        <xs:attribute ref="x" use="optional"/>
+        <xs:attribute ref="y" use="optional"/>
+        <xs:attribute ref="z" use="optional"/>
+        <xs:attribute ref="t" use="optional"/>
     </xs:complexType>
 </xs:element>