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Where Should Domain Layer Fit in a 5-Layer Architecture?

 
Greenhorn
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Two approaches from different gurus on the subject:
Floyd Marinescu
Presentation -> Application -> Services -> Domain -> Persistence
Eric Evans
Presentation -> Application -> Domain -> Infrastructure (Services & Persistence)
You can see here that Marinescu says Domain should be "underneath" Services, whereas Evans believes Domain should be above Services. I personally prefer Marinescu's scheme where the Services contains the knowledge of 1) how to persist a Domain object, 2) how to integrate persistence operations with other systems (ie sending async messages). However, isn't the following representation more consistent with Marinescu's layering?:
<---- Domain ---->
Presentation -> Application -> Services -> Persistence
The Domain layer is used across all layers and contains data and business logic/behavior. For example, it knows nothing about databases, messaging, or JNDI lookups. I do not like Evans' approache because his Domain objects contain a little persistence logic (e.g. "commit()" methods in Domain objects).
Any thoughts?
Patrick J. Nolan, Jr.
 
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It seems to me as if Floyd and Eric actually mean quite different things when they talk about "services". Do you have any links?
 
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Yah, I think that's the disconnect.
http://www.ratio.co.uk/architectural_reference_model.pdf is a nice paper on archtitectural layering that I think references the disagreement about the order of some layers. They have some neat papers on use cases, too.
http://www.surfscranton.com/architecture/ArchitecturalLayering.htm is a short page I did on the topic with some pictures based on the above.
There are MANY ways to break down layers. Most of them are useful at one time or another even on the same system.
 
Ranch Hand
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Originally posted by Patrick Nolan:

The Domain layer is used across all layers and contains data and business logic/behavior.
Any thoughts?
Patrick J. Nolan, Jr.


Figure 15. in this doc seem to support your argument.
http://www-106.ibm.com/developerworks/rational/library/content/03July/2000/2169/2169.pdf
 
Stan James
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Yes, I'd dispute "domain is used across all layers". Each layer should be nicely isolated, and should be "used by" only the layer immediately above (or below depending on how you like your dependencies.) Frameworks have exceptions, like a Logger that is used everywhere, but the domain layer should not have any exceptions.
I took "figure 15" (and the paragraphs immediately above) to mean that given a particular domain model you could build a service-style interface or a component-style interface or both. Definitions of service and component can be debated ... Fowler suggests that they are very similar but components are used within a system and services are exposed to external and/or remote clients.
I guessed that when Evans put "services & persistance" below the domain layer, he meant OS services like the system clock and the file system. Something entirely different.
 
Ilja Preuss
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There is currently an interesting discussion going on about dependencies between layers at http://www.artima.com/forums/flat.jsp?forum=106&thread=35139
 
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A high-level discussion is presented at http://www.ronin-intl.com/publications/classTypeArchitecture.htm.
- Scott
 
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