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Microsoft® Internet Explorer version 3.0 and later provides Internet Component Download services that enable users to download and install software components from the Internet and intranets. You, the software provider or Web master, can "package" applications and place them on your Web servers for download.
There are four primary methods of packaging and distributing your components to use Internet Component Download. Some methods can be combined with others to provide enhanced functionality. The method you choose will depend upon such things as the browser versions you wish to support, the type of code component you wish to distribute, the international languages your code will be distributed in, and the platforms your code will run on.
The purpose of this article is to help you decide on the appropriate combination of distribution methods for your particular Internet Component Download task. The article begins by listing the primary options and discussing the relative merits of each. The next section of the article considers the packaging and distribution decision from a problem-based perspective. Links to additional relevant articles are provided throughout the article and at the end.
This section lists the methods for distributing downloadable code components and explores the reasons for choosing one method over another.
The single executable (such as an .ocx, a .dll, or an .exe file) is downloaded, installed, and registered in one step.
Stand-alone executables:
Note that these limitations do not apply to complex setup or installation executables. It is true that with enough code, you can write an executable file that installs a Java applet on a machine running Internet Explorer 3.0 or handles software dependencies.
By pointing to the URLs of files to download, an information file (.inf) provides instructions that Internet Explorer uses to install your software. The INF file specifies the files that need to be downloaded and set up for the component to run. The INF file can also exist in a cabinet file with or without an OSD file.
Stand-alone INF files:
For more information about INF files, see Using INF Files.
The OSD vocabulary is supported by Internet Explorer version 4.0 and later. A stand-alone OSD file presents the same security/trust issue as a stand-alone .inf file. Internet Explorer will decline trust in the default browser security modes. The solution is packaging the OSD file in a cabinet file and signing the cabinet file. OSD works with Java class files and applets and can be used to specify such things as software dependencies and international language requirements.
For more information about OSD files, see the Open Software Description Overview.
Distribution units contain one or more files, all of which are downloaded together in a compressed cabinet file. You can think of distribution units as containers for components and instruction files. Cabinet files must contain an INF file, an OSD file, or both. Cabinet files usually also contain a program file. The INF and OSD files can refer to files in the cabinet file as well as to files at other URLs.
The advantages to distribution units include file compression for faster downloads and the ability to specify software dependencies, hardware platform, operating system and international language requirements. Cabinet files can be signed.
For more information about distribution units, see the Distribution Unit Overview.
This section considers the packaging and distribution decision from a problem-based perspective. The method you choose for distributing your code component will depend upon such things as the browser versions you wish to support, the type of code component you wish to distribute, the number of languages your code will be distributed in, and the number of platforms your code will run on.
Newer versions, of course, mean more code distribution options. OSD support began with Internet Explorer 3.0. Support for catalog files began with Internet Explorer 5. The following table summarizes the methods available to users with different versions of Internet Explorer.
| Code Distribution Method | Internet Explorer Version | ||
|---|---|---|---|
| 3.0 | 4.0 | 5 | |
| Stand-alone .exe | Yes | Yes | Yes |
| Stand-alone .inf file | Yes | Yes | Yes |
| Stand-alone OSD file | No | Yes | Yes |
| .cab file with .inf file | Yes | Yes | Yes |
| .cab file with OSD file | No | Yes | Yes |
| .cab file with .inf and OSD files | Yes* | Yes | Yes |
| .cab file with catalog file | No | No | Yes |
* OSD files are ignored by Internet Explorer 3.0.
Often your software will require other software to work properly. If you are distributing your software using a distribution unit, your INF file and/or OSD file can be used to define software dependencies. Dependencies cannot be specified with a stand-alone executable file. A stand-alone INF file or OSD file will work, but then you have the signing/security issue to consider. If none of your users have Internet Explorer 4.0 or later, you'll need to specify dependencies in your INF file because their browsers won't recognize OSD files.
If your software is available in English and Japanese, for example, an INF file or cabinet file with an INF file are not appropriate distribution methods. A stand-alone OSD file will work, or better yet, a cabinet file with an OSD file. The OSD vocabulary is supported by Internet Explorer 4.0 and later.
If so, one stand-alone executable will not work for you. OSD is the most flexible way of specifying platform requirements, including operating systems.
If you are distributing your component using an .exe or cabinet file over the Internet, you'll definitely want to sign it. For more information on signing components, see:
Stand-alone OSD files cannot make registry entries. You will either have to use a stand-alone executable or a cabinet file with an INF file (with or without an OSD file).
There are two very good reasons for packaging a Java applet. The first reason is to enable offline browsing of your site. Users who have your pages saved on their hard drives can browse at their leisure, frequently and efficiently. The second reason for packaging Java applets is to avoid repetitive downloads. Frequent visitors to your Web sites are downloading your applets repeatedly, wasting bandwidth and server time. The preferred way to distribute Java components is in a cabinet file with an OSD file. Java distributors must package all classes and applets that run outside the Java sandbox.
The following table summarizes the Internet Component Download packaging and distribution options, as well as the criteria for choosing an option for a particular distribution task.
| Decision Criteria | Options | |||||
|---|---|---|---|---|---|---|
| Stand-alone | .cab file with | |||||
| .exe | .inf | OSD | .inf | OSD | .inf & OSD | |
| Can make registry entries | Yes | Yes | No | Yes | No | Yes |
| Can be signed | Yes | No | No | Yes | Yes | Yes |
| Can specify language dependencies | No | No | Yes | No | Yes | Yes |
| Can specify software dependencies | No | Limited | Yes | Limited | Yes | Yes |
| Compresses files for faster download | No | No | No | Yes | Yes | Yes |
| Works with Java | No | No | Yes | No | Yes | Yes |
The following lists contain links to topics related to Internet Component Download.
Overviews
References
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