The logic of CML/LitCrit is distributed over three tiers, as is that of the original CML application. The new elements involved in CML/LitCrit, a Microsoft Outlook form and data saved in Microsoft Exchange Server, have presence on all three logical tiers.
The following diagram shows how these additional elements fit into the n-tier model followed by the CML application. Microsoft Outlook provides an additional user interface and the information store of Microsoft Exchange Server provides additional data storage. In addition, the Event Service that is part of Microsoft Exchange Server 5.5 executes business logic by acting on events in a public folder.
For more information on the distributed nature of the original CML application, see Distributed Logic and Designing the Three-Tier CML Application.