code: public boolean deleteAttribute(final String identifier,
  			final String attribute) {
  		if (identifier == null) {
  			log.error("Unable to delete an attribute with a null Identifier value.");
  			return false;
  		}
  
  		if (attribute == null) {
  			log.error("Unable to delete a null attribute.");
  			return false;
  		}
  
  		if (this.originString == null) {
  			log.error("Origin has not been set.  Cannot delete attributes without a valid origin.");
  			return false;
  		}
  
  		DeleteAttributeMessage message = new DeleteAttributeMessage();
  		message.setOrigin(this.originString);
  		message.setId(identifier);
  		message.setAttributeName(attribute);
  
  		this.session.write(message);
  		log.debug("Sent {}", message);
  
  		return true;
  	}
docs: Deletes an Attribute and its entire history from the world model. Callers
  may wish to expire the Attribute value instead.
  
  @param identifier
  the Identifier of the Attribute to expire.
  @param attribute
  the Attribute to expire.
  @return {@code true} if the message was sent successfully.