diff --git a/inventory.py b/inventory.py
new file mode 100644
index 0000000..0b831b6
--- /dev/null
+++ b/inventory.py
@@ -0,0 +1,106 @@
+# encoding: utf-8
+import sys
+import os
+import re
+import datetime
+import numpy as np
+
+from SimpaDbUtil import SqlDatabaseReader, SqlFile
+
+class Inventory( object ):
+    def __init__(self, sql_reader):
+        """
+        :param SqlDatabaseReader sql_reader: the inventory database
+        """
+        super(Inventory, self).__init__()
+        self._sql_reader = sql_reader
+        
+    def query(self, sql_query):
+        return self._sql_reader.query(sql_query)
+        
+    def machine_name_toMachine_spec_id(self, machine_name ):
+        machine_spec_id = self._sql_reader.get_table_attr( 'machines', 'name', machine_name, 'machine_spec_id' )
+        return machine_spec_id
+
+    # electricity related methods
+
+    def machine_spec_id_to_power_consumption(self, machine_spec_id ):
+        power_consumption = self._sql_reader.get_table_attr( 'machine_spec_to_power_consumption', 'machine_spec_id', machine_spec_id, 'power_consumption' )
+        return power_consumption
+
+    def get_plug_type_attr(self, plug_type, attr_name):
+        # INSERT INTO `powerplug_type_desc` (`plug_type_id`, `genre`, `max_amps`) VALUES
+        # ('iec60309_blue_pne6h_32a_m', 'm', 32.0),
+        attr_value = self._sql_reader.get_table_attr('powerplug_type_desc', 'plug_type_id', plug_type, attr_name )
+        return attr_value
+    
+    def read_plug_capacity(self, plug):
+        plug_capacity = None
+        machine_spec_id = self.machine_name_toMachine_spec_id(plug.machine.name)
+        if machine_spec_id is not None:
+            # INSERT INTO `powerplug_desc` (`machine_spec_id`, `powerplug_id`, `plug_type`) VALUES
+            # ('atos_mpdu_2901382', 'i', 'iec60309_blue_pne6h_32a_m'),                
+            rows = self._sql_reader.query("SELECT plug_type FROM powerplug_desc WHERE machine_spec_id='%s' AND powerplug_id='%s'" % (machine_spec_id, plug.name))
+            if len(rows) > 0:
+                plug_type = rows[0][0]
+                # print('plug_type : %s' % plug_type)
+                
+                plug_capacity = get_plug_type_attr(plug_type, 'max_amps')
+                #if plug_capacity:
+                #    print('plug_capacity : %f A' % plug_capacity)
+        # print("read_plug_capacity : plug capacity for plug.machine.name="+plug.machine.name+" plug="+str(plug)+" : "+ str(plug_capacity)+ "A")
+        return plug_capacity
+
+    # cluster related methods
+
+    def get_machine_purchase_date(self, machine_serial_number):
+        ordering_id = self._sql_reader.get_table_attr( 'machines', 'serial_number', machine_serial_number, 'command_id' )
+        # print(ordering_id)
+        # handle case of multiple orders
+        ordering_id = ordering_id.split('+')[0]
+        if len(ordering_id) == 0:
+            return None
+        ordering_date_as_str = self._sql_reader.get_table_attr( 'orderings', 'ordering_id', ordering_id, 'ordering_date' )
+        if ordering_date_as_str is None:
+            return None
+        if len(ordering_date_as_str) == 0:
+            return None
+        ordering_date = datetime.datetime.strptime(ordering_date_as_str, '%d/%m/%Y')
+        return ordering_date
+
+    def get_cpu_dflops(self, cpu_model):
+        '''
+        returns the number of double precision operation per second this cpu can achieve
+        ''' 
+        #INSERT INTO `cpu_specs` (`cpu_model`, `num_cores`, `clock_speed`, `dflops_per_core_per_cycle`, `comment`) VALUES
+        #('intel_xeon_x5550', 4, 2.67, 4, ''),
+        num_cores = int(self._sql_reader.get_table_attr( 'cpu_specs', 'cpu_model', cpu_model, 'num_cores' ))
+        clock_speed = float(self._sql_reader.get_table_attr( 'cpu_specs', 'cpu_model', cpu_model, 'clock_speed' )) 
+        dflops_per_core_per_cycle = int(self._sql_reader.get_table_attr('cpu_specs', 'cpu_model', cpu_model, 'dflops_per_core_per_cycle' ))
+        print(num_cores, clock_speed, dflops_per_core_per_cycle)
+        return clock_speed * dflops_per_core_per_cycle * num_cores
+    
+    def get_computer_dflops(self, computer_serial_number):
+        print(computer_serial_number)
+        num_cpus = int(self._sql_reader.get_table_attr( 'computer_to_cpu', 'serial_number', computer_serial_number, 'num_cpu' ))
+        cpu_model = self._sql_reader.get_table_attr( 'computer_to_cpu', 'serial_number', computer_serial_number, 'cpu_model' )
+        flops = num_cpus * self.get_cpu_dflops( cpu_model )
+        return flops
+    
+    def get_computer_options_price(self, computer_name):
+        options_price = 0.0
+        if computer_name == 'simpatix58' or computer_name == 'simpatix59':
+            return 7675.0 / 4 * 2 # each of these computers has 2 nvidia fermi C2050 gpus
+        return options_price
+    
+    def get_item_ownership(self, item_serial_number):
+        ownership=[]
+    
+        rows = self._sql_reader.query("SELECT * FROM ownership")
+        for row in rows:
+            (serial_number, owner, owner_ratio, comment)=row
+            if serial_number == item_serial_number:
+                ownership.append({'owner':owner, 'owner_ratio':owner_ratio})
+        return ownership
+
+