Issue 117: Marking operations as 'safe' - slide "Introduce a side-effect feature"

Side-effect WSDL feature: http://www.w3.org/2004/02/wsdl/se
One property: http://www.w3.org/2004/02/wsdl/se-type

<operation name="GetStockQuote"
           pattern="http://www.w3.org/2003/11/wsdl/in-out">
  <feature uri='http://www.w3.org/2004/02/wsdl/se'
           required='false'>
  </feature>
  <property name='http://www.w3.org/2004/02/wsdl/se-type'>
    <value>http://www.w3.org/2004/02/wsdl/se/safe</value>
  </property>
  <input message="tns:gsqReq"/>
  <output message="tns:gsqResp"/>
</operation>