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A-7E Avionics System Case Study. Utilizing Architectural Structures. An object-oriented program’s structure often bears little resemblance to its code structure. The code structure is frozen at compile-time; it consists of classes in fixed inheritance relationships. - PowerPoint PPT Presentation
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An object-oriented program’s structure often bears little resemblance to its code structure.
The code structure is frozen at compile-time; it consists of classes in fixed inheritance relationships.
A program’s runtime structure consists of rapidly changing networks of communicating objects.
The structures are largely independent and nearly impossible to understand one from the other.
The system is responsible for reading sensors and updating cockpit displays that help the pilot drop weapons on a target.
It does not fly the aircraft.
The architecture is centered around three structures: Decomposition, a structure of modules Uses, a structure of modules Process, a structure of components and
connectors The module decomposition is based on
information hiding
Goal How AchievedEase of change to: weapons, platform, symbology, input
Information hiding
Understand anticipated changes Formal evaluation procedures to take advantage of experience of domain experts
Assign work teams so that their interactions were minimized
Modules structured as a hierarchy; each work team assigned to a second-level module and all of its descedants
Hardware-Hiding Module Extended Computer Module Device Interface Module
Behavior-Hiding Module Function Driving Module Shared Services Module
Software Decision Module Application Data Type Module Data Banker Module Filter Behavior Module Physical Models Module Software Utility Module System Generation Module
Goal How AchievedIncrementally build and test system functions
Create “is-allowed-to-use” structure for programmers that limits procedures each can use
Design for platform change Restrict number of procedures that use platform directly
Produce usage guidance of manageable size
Where appropriate, define uses to be a relationship among modules
Goal How AchievedMap input to output Each process implemented as
cycle that samples inputs, computes, and presents output
Maintain real-time constraints Identify process through process structure and then perform offline scheduling
Provide results of time-consuming calculations immediately
Perform calculations in background and return most recent value when queried