Part VI -- File I/O and Driver Interface

Michael Chen
August 28, 1996
Rewritten: H. Hildreth, 9-27-96
Revised: H. Hildreth, 9-30-96

PART VI: File I/O and Driver Interface

The AIL (Abstract Implementation Layer) is only one of four layers described in the reference documentation (see ~tutorial/index.html). Up to this point we have used start events within the AIL architectures (specifically within the WebBrowser and JavaTools components) to drive the model. In preparation for adding the UIL (User Interface Layer), which will ultimately (and more accurately) drive the model, we pull the initial triggering events out of AIL and into a separate driver. We also introduce file I/O which will enable us to change resource values without recompiling.

Rapide Concepts Introduced: File I/O (the external driver is simply a common modeling technique.)

Procedure: See "type Driver is interface..." in inputoutput.rpd.

The first step was to create a driver that would, upon startup (note that each elaborated object receives a start event to which it may or may not respond), perform some I/O processing and then trigger AIL execution (by generating "ExternalStart"). An input file, ratefile, was created that contains values that are assigned to global variables; e.g., processing rate and server request workload values. These values were previously hard coded.

A higher-level architecture needed to be defined that would connect the driver to the AIL architecture. See "architecture top_level..." in inputoutput.rpd.

The ExternalStart event is connected to both clients and, in turn, to their respective WWWBrowsers. From this point in the execution, the model behaves as in Part V.

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