初探 Internet Component Download

這幾天都在研究 "Internet Component Download” 的資料，以下是一些網上資料的整理 ：

MSDN offical defination

Internet Component Download is a system service for downloading and installing software from Web sites on the Internet and intranets. This service also provides certificate checking. Internet Component Download is supported by Microsoft Internet Explorer 3.0 and later.
You, the software provider or Web master, can "package" components and place them on your Web servers for download. When users visit your Web site, Internet Component Download enables their browsers to pull down and install the programs.

Key Concept

There is some key concepts for this type of software distribution method:

• Carbinet File (.cab) – a package that include all files for the software distribution (e.g.active X controls (.ocx), dll, exe, etc.).   (詳細要怎樣打包我不懂，本身我是JAVA人，m記的東西本來就不太懂，因為工作關係我才接觸這topic)
• Packaging – Code authors need to package the software for user to download. The packaging machanism is usually a cabinet file addressed by the “codebase” attribute of an “object” element on a web page. Here is a piece of sample html code:
  <object classid="clsid:xxxx-xxxx-xxxx"
  codebase="/cab/testing.cab">
  </object>
• Signing – To protect the user from downloading software from the internet, users with user security level set to default level normally cannot download and execute the software (e.g. User Access Control, UAC, in windows 7).
  
  Digitial signature help to associate the software distribution to the code author, providing accountability for software developers.
  
  According to MSDN:
  When a user's security level is set at the default level, any object identified by the OBJECT tag on a Web page must be digitally signed. Internet Explorer's default security setting won't install a component that doesn't have a digital signature.
  
  
  This is a screen capture for the pop-up when you try to download and install an unsigned cabinet file
• Information file (.inf) – This file contain the setup information for Internet Explorer the use to install and register your software distribution. For the usage of INF file, we will discuss in another post.

Reference: MSDN - Introduction to Internet Component Download