Processing Point

Hi Markus,

   Is OPES is going to have a system, in which certain services will be 
provided 
at fixed processing points. Example : Virus scanning ay point 3.
   
   
   According to IRML, point 3 is considered, only when object couldn't be served
   from cache. Let us assume a case .
   
    There are two clients C1 and C2.
    C2 has given a rule that says : If User-Agent = Nokia 
                                                Execute Service1.
                                                
    Assume C1 asks for object www.foo.com and an entry is made for this object 
in cache. Now, C2 asks for the same object. Since the object is present in 
cache, it will be served from cache. In order to make sure that rule specified 
by C2 should be verified, it is necessary to put rule given by C2 at point 4.
    But in this case, processing of service2 wouldn't be cached.So, if C2 makes 
 
one more request for the same object, service1 would be executed once again.
    
    
    Suggestion : We can put such rules at point 3. And rules at point 3 should 
be always considered, irrespective of object coming from origin server or cache.
    This would help us in taking advantage of cache.
    
    
   Thanks
   Rajnish      
   
                                        
  
   
      
     
   Beck, Hofmann         Expires August 2001                 [Page 6] 

   Internet Draft                IRML                    February 2001 

   The "processing-point" attribute specifies at which of the four 
   points in figure 1 the rule engine on the intermediary must process 
   a rule. The four "processing-points" are derived from the Extensible 
   Proxy Services Framework as described in [2] and only apply to 
   caching proxies. Implementation architectures for other 
   intermediaries might define different or additional "processing-
   points". 
    ..................................................
       
   Point 2: Proxy Request  
        The requested Web object cannot be served from the cache and  
        the origin server is about to be contacted for the HTTP  
        resource.  
             
...........................................     
   Depending on the service type, rules may be processed and services 
   may be executed at any of the four points outlined in figure 1. A 
   virus scanning service for instance could be executed at point 3 in 
   figure 1 in order to scan all Web objects for viruses before they 
   can be stored in the cache. A URL-based request filtering service on 
   the other hand should be executed at point 1 and an ad insertion 
   service will probably be executed at point 4.