IT:AD:DDD:Components/App.AppHost

The separation of the App.Front.Presentation from App.Back.Application across two Tiers implies the following:

• The Front Tier is to be considered thing, as its application logic is practically non-existent (it concerns itself with Presentation only).
• The Back Tier’s App.Back.Application’s Services are exposed – via App.Back.Application.Facade – to the Front Tier’s App.Front.Infra.Services.Agents.
• For performance reasons, operations across the tiers are to be Chunky, not Chatty, and the results Cached in the Presentation Tier whenever reasonable.
• Requests between the Front Tier and Back Tier can be Load Balanced as required.

When the Presentation Layer requires data, it (where appropriate) invokes a Service within App.Front.Infra.Services which first checks for valid cached data within the Front Tier, and if none found creates a new Service Agent to communicate with the Back Tier’s App.Back.Application.Facade.

The Service Agents deserialize the returned streams into proxy entities defined in App.Front.Domain.Entities.

In some cases the proxy entities are cached using a Front Tier defined implementation of App.Infra.Services.ICachingService.