[OASIS Issue Tracker] Commented: (TOSCA-60) Primer - All MATERIAL Contributions

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    [ http://tools.oasis-open.org/issues/browse/TOSCA-60?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=31887#action_31887 ] 

Travis Tripp commented on TOSCA-60:
-----------------------------------

I think there should be a more crisp definition and usage of the difference between application layers and tiers.  I see the use of the term tier used quite a bit in the document (section 3 in particular) and wanted to provide some perspective on what terminology we have adopted internally: Application Layers are distinct from distribution Tiers.  Take a look at the below snippet from the Microsoft Application Architecture guide:

"It is important to understand the distinction between layers and tiers. Layers describe the logical groupings of the functionality and components in an application; whereas tiers describe the physical distribution of the functionality and components on separate servers, computers, networks, or remote locations. Although both layers and tiers may use the same set of names (presentation, business, services, and data), only tiers imply a physical separation. It is quite common to locate more than one layer on the same physical machine (the same tier). You can think of the term tier as referring to physical distribution patterns such as two-tier, three-tier, and n-tier." -Source MSDN (http://msdn.microsoft.com/en-us/library/ee658109.aspx).

Here are additional references where we've seen this terminology:
•	http://pic.dhe.ibm.com/infocenter/wchelp/v6r0m0/index.jsp?topic=%2Fcom.ibm.commerce.developer.doc%2Fconcepts%2Fcsdapplication.htm
•	http://www.lhotka.net/WeBlog/PermaLink.aspx?guid=efa88d0a-2388-4909-bee1-c9bddb6e9868
•	http://codingarchitect.wordpress.com/2009/09/09/layers-vs-tiers/
•	https://www.google.com/search?q=layer+vs+tier

At its most simple, many layers may be deployed to the same physical tier or separated to different tiers.  We think of it more as a layer being a logical unit that you may want to deploy or manage separately and it is up to the designer to determine how granular to make the layer definition. Each layer definition may contain actual artifacts to deploy to systems or it may just be scripts / flows related to configuration that occur as part of an action on this layer. These layers are mapped to a deployment topology which ultimately is bound to platform / infrastructure tiers.

> Primer - All MATERIAL Contributions 
> ------------------------------------
>
>                 Key: TOSCA-60
>                 URL: http://tools.oasis-open.org/issues/browse/TOSCA-60
>             Project: OASIS Topology and Orchestration Specification for Cloud Applications (TOSCA) TC
>          Issue Type: Task
>          Components: Primer 
>            Reporter: Paul Lipton 
>            Assignee: Dale Moberg
>
> This issue is a bucket for ALL MATERIAL contributions such as explanatory paragraphs, examples, etc. 
> IMPORTANT:  ALL contributions will be aggregated by the Primer editors and considered for approval by the TC, although they may work with contributors to align style, format, etc. No contribution will be discarded without the approval of the contributor.  
> * See this email for details on the Primer development process, etc.: https://www.oasis-open.org/apps/org/workgroup/tosca/email/archives/201211/msg00003.html) 
> See TOSCA-16 for ALL NON-MATERIAL suggestions such as spelling and grammar changes. 

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