What is meant by open and closed tiered architecture?

Question

I know this probably sounds like a very trivial question, but I could not find any resources on the Internet.

Could you tell me what open and closed layered architectures are and why open layered architecture seems to be the most difficult to use? Are there any disadvantages to using closed / open layered architectures?

Answer 1

Closed multi-level architecture means that any given level (or level) can use only the services of the next nearest layer, whereas in an open-level architecture this layer can use any of the layers (or levels) below it, the architecture of a closed layer promotes independence between levels by reducing dependencies.

http://books.google.com/books?id=z5XX4gYuMs0C&pg=PT160&lpg=PT160&dq=%22closed+layer+architecture%22&source=bl&ots=-iCw2be77_&sig=zQvScA2oIud_rNJNMziZXNMSnJo&hl=en&ei=u4UZSt7MKoX2tAOW-8jaCA&sa=X&oi=book_result&ct=result&resnum=5# PPT160, M1

Answer 2

Here is one of the earliest definitions of open and closed architectures from Bob Martin:

http://www.objectmentor.com/resources/articles/ocp.pdf

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