“Layers”和“Tiers”的区别是什么?


当前回答

从技术上讲,Tier可以是代码运行所需的一种最小环境。

例如,假设一个3层应用程序可以运行

3 physical machines with no OS . 1 physical machine with 3 virtual machines with no OS. (That was a 3-(hardware)tier app) 1 physical machine with 3 virtual machines with 3 different/same OSes (That was a 3-(OS)tier app) 1 physical machine with 1 virtual machine with 1 OS but 3 AppServers (That was a 3-(AppServer)tier app) 1 physical machine with 1 virtual machine with 1 OS with 1 AppServer but 3 DBMS (That was a 3-(DBMS)tier app) 1 physical machine with 1 virtual machine with 1 OS with 1 AppServers and 1 DBMS but 3 Excel workbooks. (That was a 3-(AppServer)tier app)

Excel工作簿是运行VBA代码所需的最低环境。

这3个工作簿可以放在一台物理计算机上,也可以放在多个物理计算机上。

我注意到,在实践中,人们在应用描述上下文中说“层”时,指的是“操作系统层”。

也就是说,如果一个应用运行在3个不同的操作系统上,那么它就是一个3层应用。

所以从学究角度来说,描述应用程序的正确方法是

“1至3层能力,运行在2层”应用程序。

:)


层只是应用程序中职责功能分离的代码类型(例如,表示,数据,安全等)。

其他回答

我使用层来描述我的解决方案组件中的架构师或技术堆栈。通常在涉及网络或进程间通信时,我使用层对这些组件进行逻辑分组。

层是概念实体,用于从逻辑角度分离软件系统的功能;当你实现系统时,你使用不同的方法组织这些层;在这种情况下,我们不称它们为层,而是称它们为层。

我喜欢下面来自微软应用程序架构指南2的描述

层描述了应用程序中功能和组件的逻辑分组;而层描述了功能和组件在独立服务器、计算机、网络或远程位置上的物理分布。尽管层和层使用相同的名称集(表示、业务、服务和数据),但请记住,只有层意味着物理分离。

IBM的三层体系结构文章有一个章节专门讨论这个主题:

In discussions of three-tier architecture, layer is often used interchangeably – and mistakenly – for tier, as in 'presentation layer' or 'business logic layer.' They aren't the same. A 'layer' refers to a functional division of the software, but a 'tier' refers to a functional division of the software that runs on infrastructure separate from the other divisions. The Contacts app on your phone, for example, is a three-layer application, but a single-tier application, because all three layers run on your phone. The difference is important, because layers can't offer the same benefits as tiers.

我发现一个定义说,层是逻辑分离,层是物理分离。