Architectural Design-Development and Software Engineering-Lecture Slides, Slides of Software Engineering

Download Architectural Design-Development and Software Engineering-Lecture Slides and more Slides Software Engineering in PDF only on Docsity! Architectural Design - Establishing the Overall Structure of a Software System Topics covered:  System structuring  Control models  Modular decomposition  Multiprocessor architectures  Client-server architectures  Distributed object architectures Architectural Design Distributed Systems Architectures 1 COMP201 - Software Engineering docsity.com 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 2 COMP201 - Software Engineering docsity.com 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 5 COMP201 - Software Engineering docsity.com Architectural Models  Different architectural models may be produced during the design process  Each model presents different perspectives on the architecture:  Static structural model  Dynamic process model  Interface model  Relationships model 6 COMP201 - Software Engineering docsity.com Architectural Models  Static structural models show the major system components  Dynamic process models show the process structure of the system  Interface models define sub-system interfaces  Relationships models such as a data-flow model 7 COMP201 - Software Engineering docsity.com Another Example 10 COMP201 - Software Engineering  Question: What subsystems may be identified in a library system with a web based interface and how might they interact? docsity.com The 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 11 COMP201 - Software Engineering docsity.com Client-Server Architecture  Distributed system model which shows how data and processing is distributed across a range of components:  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 12 COMP201 - Software Engineering docsity.com Abstract Machine Model - Used to model the interfacing of sub-systems  Organises the system into a set of layers (or abstract machines) each of which provide a set of services  Supports the incremental development of sub-systems in different layers. When a layer interface changes, only the adjacent layer is affected  However, it is often difficult to structure systems in this way 15 COMP201 - Software Engineering docsity.com ISO/OSI Network Model Application Presentation Session Transport Network Data link Physical 7 6 5 4 3 2 1 Communica tions medium Network Data link Physical Application Presentation Session Transport Network Data link Physical Appl 16 COMP201 - Software Engineering docsity.com Control Models Control Models are concerned with the control flow between sub systems:  Centralised control  One sub-system has overall responsibility for control and starts and stops other sub-systems  Event-based control  Each sub-system can respond to externally generated events from other sub-systems or the system’s environment 17 COMP201 - Software Engineering docsity.com Centralised Control  If the controlled subsystems run in parallel, then we may use the manager model of centralised control:  Manager model  Applicable to concurrent systems. One system component controls the stopping, starting and coordination of other system processes. Can also be implemented in sequential systems as a case statement. 20 COMP201 - Software Engineering docsity.com Real-Time System Control System controller User interface Fault handler Computation processes Actuator processes Sensor processes 21 COMP201 - Software Engineering docsity.com Event-Driven Systems  Driven by externally generated events where the timing of the event is out of the control of the sub-systems which process the event  There are two principal event-driven models:  Broadcast models. An event is broadcast to all sub-systems. Any sub-system which can handle the event may do so  Interrupt-driven models. Used in real-time systems where interrupts are detected by an interrupt handler and passed to some other component for processing 22 COMP201 - Software Engineering docsity.com Interrupt-Driven Systems  Used in real-time systems where fast response to an event is essential  There are known interrupt types with a handler defined for each type  Each type is associated with a memory location and a hardware switch causes transfer to its handler  Allows fast response but complex to program and difficult to validate 25 COMP201 - Software Engineering docsity.com Interrupt-Driven Control Handler 1 Handler 2 Handler 3 Handler 4 Process 1 Process 2 Process 3 Process 4 Interrupts Interrupt vector 26 COMP201 - Software Engineering docsity.com Modular Decomposition  Another structural level where sub-systems are decomposed into modules  Two modular decomposition models covered  An object model where the system is decomposed into interacting objects  A data-flow model where the system is decomposed into functional modules which transform inputs to outputs. Also known as the pipeline model  If possible, decisions about concurrency should be delayed until modules are implemented 27 COMP201 - Software Engineering docsity.com Data-Flow Models  Functional transformations process their inputs to produce outputs  May be referred to as a pipe and filter model (as in UNIX shell)  Variants of this approach are very common. When transformations are sequential, this is a batch sequential model which is extensively used in data processing systems  Not really suitable for interactive systems 30 COMP201 - Software Engineering docsity.com Invoice Processing System Read issued invoices Identify payments Issue receipts Find payments due Receipts Issue payment reminder Reminders Invoices Payments 31 COMP201 - Software Engineering docsity.com