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Notes on Patterns(1)

1.Patterns are of contexts, problems and solutions, their relationship is as below:

Pattern:(1)Context : design situation giving rise to a design problem(2)Problem : set of forces arising in the context(3)Solutions : Configure to balance the forces. It's of [1] Sturctures with components and relationships; [2] Run-time behaviour

The phiolosophy of Patterns is to find some stable point among the balances of software development, I think.

2.Layer
Architectural Patterns one : Layer.The Layer Pattern helps to structure applications that can be decomposed into groups of subtasks in which each group of subtasks is at a particular level of abstractioin.

It's architecture of software, such as OSI, TCP/IP layer structure.

To design Layer Pattern, we should consider about something as below:1) The interfaces between layers;2) The abstraction of each isolated layers

3.Broker
The Broker pattern is of 6 parts:Server, Client, Broker, Server-Side Proxy, Client-Side Proxy, and Bridge.

The main idea of Broker is to separate the different roles in a communication system. Different sides of the communication system may have data and message in different formatics or different structures, the communication among them, it is very difficult and complex for every peer to store all the formatics and structures, and it is also very difficult to unify the formatics and structures, so Broker induced.

Broker remember the all the formatics and structures, send and receive different types of messages from or to different peers. Broker make client and server do their own jobs despite the communication processes.

4.Model-View-Controller
ModelThe Model-View-Controller Model(MVC) devided a interactive application into 3 components. The core functionailties and data composes Model, the display information composes View, the user inputs compose Controller.

The separation of model from view and controller allows mutiple views of the same model.

The change-propagation mechanism is the only link between model, view and controller. Model provides functions for the core functionalities, and also provides functions for View and Controller to use and mechanisms to notify them.

5.Presentation-Abstraction-Control
The PAC (Presentation-Abstraction-Control) Architecture Pattern defines a structure for interactive software systems in the form of a hierachy of cooperating agents. Each agents composes of presentation, abstraction and control.

Different from MVC, PAC pattern is to separate the software into different Layers, it's like Layers pattern, but for Interactive Structure.
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