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Transcript of Chapter 4

Modeling and Detection of Camouflaging Worm

2012

CHAPTER 4

SYSTEM DESIGNSystems design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements. It implies a systematic and rigorous approach to designan approach demanded by the scale and complexity of many systems problems. The purpose of System Design is to create a technical solution that satisfies the functional requirements for the system. At this point in the project lifecycle there should be a Functional Specification, written primarily in business terminology, containing a complete description of the operational needs of the various organizational entities that will use the new system. The challenge is to translate all of this information into Technical Specifications that accurately describe the design of the system, and that can be used as input to System Construction. The Functional Specification produced during System Requirements Analysis is transformed into a physical architecture. The purpose of System Design is to create a technical solution that satisfies the functional requirements for the system. At this point in the project lifecycle there should be a Functional Specification, written primarily in business terminology, containing a complete description of the operational needs of the various organizational entities that will use the new system. The challenge is to translate all of this information into Technical Specifications that accurately describe the design of the system, and that can be used as input to System Construction. The Functional Specification produced during System Requirements Analysis is transformed into a physical architecture. System components are distributed across the physical architecture, usable interfaces are designed and prototyped, and Technical Specifications are created for the Application Developers, enabling them to build and test the system. System design contains Logical Design & Physical Designing, logical designing describes the structure & characteristics or features, like output, input, files, database & procedures. The physical design, which follows the logical design, actual software & a working system. There will be constraints like Hardware, Software, Cost, Time & Interfaces.

Department of Computer Science & Engg, SaIT

Page 1

Modeling and Detection of Camouflaging Worm

2012

System Design involves the analysis, design, and configuration of the necessary hardware and software components to support your solution's architecture. The five major components of System Design include: the Information Model, Community Model, Security/Permission Model, System Integration, Workflow, and Technical Architecture. A System Design typically provides the following benefits: Improved system performance; individually tailored configuration advice

demonstrates where improvement is necessary, and how to improve the system to regain lost performance. Customers gain a detailed understanding of how their users use their system. This Usage Profile can be leveraged to develop future architecture changes. Potential to learn of future concerns, allowing customers to take proactive measures to avoid problems. A baseline performance level is established against which benefits can be compared and changes to the system predicted or foreseen.

System design is the process of working out the overall functionality and approach that the system will include. It starts at a high level and then drills down into great detail, and normally ends up with the production of a technical specification. The design is the process of designing exactly how the specifications are to be implemented. Analysis and design are very important in the whole development cycle. Any fault in the design could affect the product or could be very expensive to solve in the later stage of software development. System Design is the activity of proceeding from an identified set of requirements for a system to a design that meets those requirements. A distinction is sometimes drawn between high-level or architectural design, which is concerned with the main components of the system and their roles and interrelationships, and detailed design, which is concerned with the internal structure and operation of individual components. The term system design is sometimes used to cover just the high-level design activity. System components are distributed across the physical architecture, usable interfaces are designed and prototyped, and Technical Specifications are created for the Application. Developers, enabling them to build and test the system.

Department of Computer Science & Engg, SaIT

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Modeling and Detection of Camouflaging Worm

2012

The system design are broadly classified into two categories : high level design and low level design.

High Level Design :A high-level design provides an overview of a solution, platform, system, product, service, or process. Such an overview is important in a multi-project development to make sure that each supporting component design will be compatible with its neighboring designs and with the big picture. The highest level solution design should briefly describe all platforms, systems, products, services and processes that it depends upon and include any important changes that need to be made to them. A high-level design document will usually include a high-level architecture diagram depicting the components, interfaces and networks that need to be further specified or developed. The high-level design defines the project level architecture of the system. This architecture defines the sub-systems to be built, internal and external interfaces to be developed, and interface standards identified. The high level design is where the subsystem requirements are developed. The high-level design also identifies the major candidate off-the-shelf products that might be used in the system. High-level design is the transitional step between what [requirements for subsystems] the system does, and how [architecture and interfaces] the system will be implemented to meet the system requirements. This process includes the decomposition of system requirements into alternative project architectures and then the evaluation of these project architectures for optimum performance, functionality, cost, and other issues [technical and non-technical]. Stakeholder involvement is critical for this activity. In this step, internal and external interfaces are identified along with the needed industry standards. These interfaces are then managed throughout the development process. The following uses ramp metering as an example for the two key decomposition activities: Functional decomposition is breaking a function down into its smallest parts. [E.g., ramp metering includes the sub-functions of detection, meter rate control, main line metering, ramp queuing, time of day, and communications]. Physical decomposition defines the physical elements needed to carry out the function. [E.g., ramp metering decomposition includes loops, controller clock, fiber or twisted pair for communications, 2070 controllers, host computers, cabinets, and conduits].

Department of Computer Science & Engg, SaIT

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Modeling and Detection of Camouflaging Worm

2012

Finally, allocating these sub-functions to the physical elements of the system will form the complete project architecture. This step also defines the integration and verification activities needed when the system elements are developed. The high-level design of a software system is a collection of module and subroutine interfaces related to each other by means of USES and IS_COMPONENT_OF relationships. The High Level Design Document is a pretty important document for a project, covering at a high level the overall design of the solution. If one were to try and present a very succinct summary of the High Level Document, it could be something like this: Detailed use case scenarios of key process flows of the application The class model and relationships The sequence diagrams which outline key use case scenarios The data/object model with relational table design User interface style and design After the requirements definition the high level design is the most important document and provides the blueprint for the further stages of a project including the detailed design and implementation stages. By not getting the high level design right, organisations run the risk of creating problems which could be extremely expensive to remedy at a later stage. The purpose of this High Level Design (HLD) Document is to add the necessary detail to the current project description to represent a suitable model for coding. This document is also intended to help detect contradictions prior to coding, and can be used as a reference manual for how the modules interact at a high level. The HLD documentation presents the structure of the system, such as the database architecture, application architecture (layers), application flow (Navigation), and technology architecture. The HLD uses non-technical to mildly-technical terms which should be understandable to the administrators of the system. The document may also depict or otherwise refer to work flows and/or data flows between component systems. In addition, there should be brief consideration of all significant commercial, legal, environmental, security, safety and technical risks, issues and assumptions. The idea is to mention every work area briefly, clearly delegating the ownership of more detailed design activity whilst also encouraging effective collaboration between the various project teams.

Department of Computer Science & Engg, SaIT

Page 4

Modeling and Detection of Camouflaging Wo