Correlation Issue

1
Correlation Issue
Seller
BSChannelType
Buyer
SDChannelType
DBChannelType
Distributor
2
Correlation Issue

• Buyer places order with POId as BSChannelType
  Identifier
• Seller places order with Distributor to
  distribute goods to Buyer using InvoiceId as
  SDChannelType Identifier
• Distributor sends delivery details to Buyer on
  DBChannelType with Identifier as DeliveryId

Problem How can the Buyer determine that the
message from the Distributor is for a specific
Purchase Order?
3
Correlation Issue

• Supposing the Buyer buys a Car and Washing
  machine more-or-less at the same time but as two
  separate business transactions. For example buyer
  acting on behalf of two different customers. Thus
  two different choreos. The messages from the
  Distributor with Identifiers on the channel
  instances are Delivery1 and Delivery2.
• The Buyer has no way of knowing which delivery
  belongs to which conversation.

4
Correlation Issue
Seller
BSChannelTypePO1
Buyer
BSChannelTypePO2
SDChannelTypeINV2
DSChannelTypeDEL2
SDChannelTypeINV1
DSChannelTypeDEL1
Distributor
5
Correlation Issue
From the Buyers perspective we see the following
interactions based on their channel
identities. Because the identifiers have no
relationship we cannot figure out which
interaction belongs with which
6
Correlation Issue

• Solution 1
• Require all roles to adopt the same Id for
  Channel Instances
• ves
• Works and is simple
• -ves
• Big restriction that may not work in practice

• Solution 2
• Provide some sort of session encoding to channels
  with identifier evolution
• ves
• Works
• Few restrictions
• -ves
• More complex (Channel Identity needs to be
  preserved)
• Onus on designer

7
Correlation Issue

• Solution 3
• Channel Passing
• ves
• Simple
• -ves
• Forces a particular design idiom