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Using IntelliStream Technology
With IntelliStream technology, the application deployer can include in the initial download only those application files needed to start the application. Then, as the end user runs other parts of the application, WebClient automatically downloads and installs the additional files as needed.
IntelliStream also works every time the end user starts an application by checking for updated application components, downloading them, and installing them — all before the application starts.
When an application component reaches the end user’s machine, either as part of the initial download or as part of an update, the files within the component are cached.
For more information on IntelliStream, see Deploying an Application."
Advantages of Using IntelliStream
Using IntelliStream provides the following advantages:
- The initial download and subsequent upgrades do not requiring special installation procedures or update procedures.
- The initial download need not contain all components of the application. Thus, the end user’s machine is not cluttered with application components that are never used.
- When the application deployer updates the application, WebClient on the end user’s machine automatically downloads only the application-component elements that have changed, making downloads faster.
- Application components (for the initial download and for updates) can be hosted on an AppServer as well as on a Web server.
Codebase Locator
As part of defining the application to WebClient, the application deployer, using the Application Assembler, describes the server that contains the application components (for the initial download and for updates) to be downloaded. This description is called the codebase locator, which is used by WebClient to access this server, called the codebase server.
For more information, see Designing the Deployment Configuration."
Components and Download Mode
To download the files of the client portion of the application, WebClient places them in Microsoft cabinet files. Typically, a single cabinet file might contain several procedure (
.r
) or procedure library (.pl
) files, image files, etc. A single cabinet file comprises an application component.The application deployer assigns each application component one of the following download modes:
At Startup
— The component is included in the initial download.As Needed
— The component is automatically downloaded by WebClient when the end user uses the part of the application that references it.Ask User at Startup
— At the time of the initial download, WebClient asks the end user which as-requested components they want. WebClient then downloads them (along with the at-startup components).For more information, see Deploying an Application."
Component Update Files
When the application deployer defines a new version of an application to the Application Assembler, the Application Assembler automatically creates a component update file for each component whose new version is different from a previous version. (A new version of a component is different from a previous version when any application file residing in the component has changed.) Each component update file represents the delta (difference) between the new version of a component and the previous version of the same component.
When WebClient on the end user’s machine determines that the end user’s version of the application needs updating, WebClient downloads the component update files that update the version on the end user’s machine to the newest version.
For more information, see Deploying an Application."
Determining if a Resource was Modified
When the application deployer generates a new version of an application using the Application Assembler, the Application Assembler determines if an r-code resource has changed since the last version by comparing the MD-5 value for the r-code with the MD-5 value from the previous version, which the Application Assembler stores in a version-information file. (MD-5 is an algorithm that reads a file and produces a short mathematical value. If a file changes even slightly, MD-5 produces a different mathematical value. By comparing the MD-5 values of two files, you can quickly determine if they are identical or different.) For more information on the version-information file, see Deploying an Application."
When compiling procedures, be sure to specify the Generate MD-5 option. If you do not, MD-5 values are not inserted into r-code resources, forcing the Application Assembler to check for changes much more coarsely (by comparing time stamps, which might cause unnecessary downloads.
Obsolete Versions
When a new version of the application is defined, certain previous versions can be defined as obsolete. For example, you might define as obsolete a version you no longer support that all end users have upgraded from. When WebClient generates a new version, it does not produce component update files for obsolete versions.
For more information, see Deploying an Application."
System Tasks and 4GL Routine Facilities
The IntelliStream System Tasks facility (in the Application Assembler) can perform an array of built-in installation tasks, such as creating desktop shortcuts and registering system files. In addition to the System Tasks facility, WebClient can invoke a 4GL routine you supply to perform additional installation tasks. For more information on these facilities, see Deploying an Application."
Digital Signatures
WebClient lets the application deployer digitally sign each file to be downloaded. Then, when the end user downloads a file, WebClient on the end user’s machine validates the digital signature.
For complete information on digital signatures in general and how WebClient uses them in particular, see Designing Security."
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