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Architectural Design 1

Software Architecture. The design process for identifying the sub-systems making up a system and the framework for sub-system control and communication is architectural design.The output of this design process is a description of the software architecture.. Architectural Design. An early stage of

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Architectural Design 1

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    1. Architectural Design (1) Yonsei University 2nd Semester, 2003 Sang-Hyun Park

    2. Software Architecture The design process for identifying the sub-systems making up a system and the framework for sub-system control and communication is architectural design. The output of this design process is a description of the software architecture.

    3. Architectural Design An early stage of the system design process Represents the link between specification and design processes Often carried out in parallel with some specification activities It involves identifying major system components and their communications.

    4. Architectural Design Process System structuring The system is decomposed into several principal sub-systems and communications between these sub-systems are identified. Control modeling A model of the control relationships between the different parts of the system is established. Modular decomposition The identified sub-systems are decomposed into modules.

    5. Sub-Systems and Modules A sub-system is a system in its own right whose operation is independent of the services provided by other sub-systems. A module is a system component that provides services to other components but would not normally be considered as a separate system.

    6. Architectural Models Different architectural models may be produced during the design process. Each model presents different perspectives on the architecture. Static structure model that shows the major system components Dynamic process model that shows how the system is organized into processes at run time. Interface model that defined sub-system interfaces Relationship model that show relationships such as data flow between sub-systems

    7. Architectural Styles The system architecture affects the performance, robustness, and maintainability of a system. Therefore the particular style and structure chosen for an application may depend on the non-functional system requirements. Performance localize operations to minimize sub-system communication Security use a layered architecture with critical assets in inner layers Availability include redundant components in the architecture Maintainability use fine-grain, self-contained components

    8. System Structuring Concerned with decomposing the system into interacting sub-systems The architectural design is normally expressed as a block diagram presenting an overview of the system structure. (Figure 10.1) More specific models of the structure may be developed which show how systems share data, how they are distributed and how they interface with each other.

    9. Repository Model Sub-systems must exchange data. This may be done in two ways: Shared data is held in a central database or repository and may be accessed by all sub-systems Each sub-system maintains its own database and passes data explicitly to other sub-systems When large amounts of data are to be shared, the repository model of sharing is most commonly used.

    10. CASE Toolset Architecture

    11. Repository Model Characteristics Advantages Efficient way to share large amounts of data Sub-systems which produce data need not be concerned with how that data is used by other sub-systems. Activities such as backup, security, access control and recovery from error are centralized. Sharing model is published as the repository schema

    12. Repository Model Characteristics Disadvantages Sub-systems must agree on a repository model. Evolution is difficult and expensive. No scope for specific management policies Difficult to distribute the repository over a number of machines

    13. Client-Server Architecture Distributed system model which shows how data and processing are distributed across a range of processors. Set of stand-alone servers which provide specific services such as printing, data management, etc. Set of clients which call on these services Network which allows clients to access servers

    14. Film and Picture Library

    15. Client-Server Characteristics Advantages Distribution of data is straightforward. Make effective use of networked systems. May require cheaper hardware. Easy to add new servers or upgrade existing servers Disadvantages No shared data model so sub-systems use different data organization. Data interchange may be inefficient. Redundant management in each server No central register of names and services – it may be hard to find out what servers and services are available

    16. Abstract Machine Model Models the interfacing of sub-systems Organizes the system into a set of layers each of which provides a set of services Each layer defines an abstract machine whose machine language (the services provided by the layer) is used to implement the next level of abstract machine. When a layer interface changes, only the adjacent layer is affected. However, often difficult to structure systems in this way

    17. Version Management System

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