January 20, 2016 / Dennis Holinka
Topic 1 – Stack overview
This week's posts go over the Stack of Enterprise Architecture and the components that it is composed of.
Post 1 - Styles: Layers and the relation to the Stack
The EA Stack overview and its structure are founded in the concept of using Architectural Styles. Styles are a form of representing lessons from experience in systems design and form the primary elements in defining concepts on which a system's architecture is built. Styles are used in general to reflect architectural patterns that consist of decisions and constraints from specific design contexts. One of the most popular used architectural styles is the Layered Style and it is on this particular style that the EA stack is represented. Layered architecture style uses ordered layers that are separated in which one layer may obtain services from a layer below. Specifically, the layers of the Enterprise Information Technology Architecture are separated into four layers in which one layer in abstract, provides a set of services to the layer above. This is similar to the way virtual machines are layered to have one ordered layer provide services to the one above all the way up to stack. In this particular example diagram, the layers are placed adjacent to each other in order to convey the ability of each layer able to receive services from them. There are many layered style architecture models for EA in which the layers are called either BDAT for business, data, application, and technology or BIDAT for Business, Information, Data, and Technology are used. The point is that it is used to group related functionality for the aggregation of responsibility. There are two types of layering: strict and relaxed which constrains the way the layers are allowed to communicate. The diagram presented as part of the course is another way to represent vertical layering in a relaxed manner which allows a layer to communicate within itself and any lower layer.
Many architects are familiar with the OSI communications reference model which consists of seven layers that are linked in service in order to communicate the organizing logic of the communication stack from the application to the physical medium that communicates the bits. Similarly, EA is ordered into business, information, application, and technology infrastructure in order to provide the organizing logic of the enterprise or part of the enterprise represented in its business architecture as a system component. It is from here that many industry experts have drawn the connection that the enterprise can be ordered in layers, just as a systems architecture is ordered to provide transparency into the lineage and traceability between the layers to the physical infrastructure run-time.
Diagram: Retrieved from https://psu.instructure.com/courses/1772177/files/77042589/preview
Many architects are familiar with the OSI communications reference model which consists of seven layers that are linked in service in order to communicate the organizing logic of the communication stack from the application to the physical medium that communicates the bits. Similarly, EA is ordered into business, information, application, and technology infrastructure in order to provide the organizing logic of the enterprise or part of the enterprise represented in its business architecture as a system component. It is from here that many industry experts have drawn the connection that the enterprise can be ordered in layers, just as a systems architecture is ordered to provide transparency into the lineage and traceability between the layers to the physical infrastructure run-time.
Diagram: Retrieved from http://nsgn.net/osi_reference_model/images/diagram4.jpg
References: https://msdn.microsoft.com/en-us/library/ee658117.aspx#LayeredStyle
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