The Systems Engineering Context Chapter 1 The Systems Engineering Context Winter 2007 SEG2101 - Chapter 1

What Is Systems Engineering? Systems Engineering is an interdisciplinary approach and means to enable the realization of successful systems. It focuses on defining customer needs and required functionality early in the development cycle, documenting requirements, then proceeding with design synthesis and system validation while considering the complete problem: Operations Performance Test Manufacturing Cost & Schedule Training & Support Disposal Systems Engineering integrates all the disciplines and specialty groups into a team effort forming a structured development process that proceeds from concept to production to operation. Systems Engineering considers both the business and the technical needs of all customers with the goal of providing a quality product that meets the user needs. Winter 2007 SEG2101 - Chapter 1

Systems Engineering Context The problem Major principles of systems engineering Managing the system evolution Winter 2007 SEG2101 - Chapter 1

1.1: The Problem Symptoms Reasons Quality Traditional approach Winter 2007 SEG2101 - Chapter 1

Symptoms The quality and cost of software has been a growing concern Delivered long behind schedule At much higher cost than anticipated Without giving the desired benefits and user satisfaction Winter 2007 SEG2101 - Chapter 1

Reasons It is hard to understand the purpose of a system well enough to plan its functionality in advance so that it will really satisfy the user needs. The complexity of systems and their dynamic behavior is too high. The visibility nature of the product makes the development and maintenance process itself difficult to understand and control. There is a lack of proven components to use as high level building blocks. Too much is developed from scratch. Winter 2007 SEG2101 - Chapter 1

Concepts User: all those who interact directly with the system and use the system service to achieve some operative purpose. Owner: people that will either own or be responsible for the system during part of its lifetime. Subject: known to the system but does not directly interact with it. (e.g. people and objects represented in a database) Developer: people that actually develop the system. Winter 2007 SEG2101 - Chapter 1

System Quality System quality is the systems ability to satisfy the needs and expectations of the user and the owners, i.e. the system environment. Quality depends on clear and unambiguous communication. Winter 2007 SEG2101 - Chapter 1

Quality Winter 2007 SEG2101 - Chapter 1

Communication Problem Winter 2007 SEG2101 - Chapter 1

Essence of Quality Control To ensure that each communication link and transformation step worked as intended. Overall process: the organization of the development process into major steps where specific documents are produced and certain quality assessment procedures performed. Technical content: the information content in the various documents, e.g. requirements specification, system specification, and test plans. Winter 2007 SEG2101 - Chapter 1

The Traditional Approach Winter 2007 SEG2101 - Chapter 1

1.2: Major Principles of System Engineering Methodology Descriptions Main descriptions Winter 2007 SEG2101 - Chapter 1

Methodology (I) Systems engineering is performed by a system consisting of people and tools called the project system or the engineering organization. The end results of systems engineering are target systems and their documentation, in the form of descriptions. The role of a systems engineering methodology is to help the engineering organization make target systems right the first time and every time, within budget and on time. Winter 2007 SEG2101 - Chapter 1

The Role of Methodology Winter 2007 SEG2101 - Chapter 1

Methodology (II) A methodology is made up of a set of methods each of which is a systematic way of producing some result. A methodology prescribes a set of descriptions and associated methods. Each method provides guidelines for structuring and using descriptions in given notations. A methodology is a collection of methods that a system organization uses to achieve right quality, short lead time and low cost. Winter 2007 SEG2101 - Chapter 1

Descriptions Symbolic representations of the subject matters Winter 2007 SEG2101 - Chapter 1

Main Descriptions (I) Winter 2007 SEG2101 - Chapter 1

Main Descriptions (II) Why the system is needed Requirements specification What its functionality should be Functional design How it should be implemented Implementation design Winter 2007 SEG2101 - Chapter 1

Requirements Specification Clarify the needs of the user and the owner Write the needs down as requirements The requirements can be clearly understood by the user, the owner, and the developer Focus on the purpose and role of the system Two categories: functional requirements and non-functional requirements Winter 2007 SEG2101 - Chapter 1

Non-Functional Requirements Winter 2007 SEG2101 - Chapter 1

Functional Design Define the system functionality as clearly and completely as possible Define the architecture of the technical solution that will be used to realize the functionality Be represented as functional design and implementation design Winter 2007 SEG2101 - Chapter 1

Implementation Design Focuses on the technical solution and its relation to the functional design Forms the basis of the implementation of the concrete system consisting of hardware and software Tells how the system is going to be realized Is derived from the functional design and the non-functional requirements Winter 2007 SEG2101 - Chapter 1

Process Quality The conformance between the requirement specification and the system. Process quality vs system quality Winter 2007 SEG2101 - Chapter 1

Quality Assurance Winter 2007 SEG2101 - Chapter 1

Benefits of Systems Engineering (I) Step-wise quality assurance can be performed during the entire development. The user and owner needs are put into focus. The functionality can be validated at an early stage. The number of aspects to be considered at each step is reduced. The cost of error correction is reduced since error can be detected earlier. Winter 2007 SEG2101 - Chapter 1

Benefits of Systems Engineering (II) Different descriptions corresponds to different kinds of expert knowledge. Language can be selected to fit the specific purpose of each description. Description can be modified without affecting each other. The functional design documents the system as whole independently of the implementation technology chosen for the various parts. Each step provides a firm foundation for the next step. Winter 2007 SEG2101 - Chapter 1

1.3: Managing the System Evolution Reference model (waterfall model) Documents Winter 2007 SEG2101 - Chapter 1

Waterfall Model Winter 2007 SEG2101 - Chapter 1

Concepts Activity: the means of producing results Phase: period of time where specific activities are carried out and results produced Baseline: phase result, basis for future work Milestone: phase transition Winter 2007 SEG2101 - Chapter 1

Milestones and Baselines Winter 2007 SEG2101 - Chapter 1

Maintenance Winter 2007 SEG2101 - Chapter 1

Activity Model Winter 2007 SEG2101 - Chapter 1

Documents Winter 2007 SEG2101 - Chapter 1