1. The Systems Engineering Context
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The Systems Engineering Context
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2. 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.
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3. Systems Engineering Context
The problem
Major principles of systems engineering
Managing the system evolution
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4. 1.1: The Problem Symptoms Reasons Quality Traditional approach
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5. 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
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6. 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.
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7. 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.
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8. 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.
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9. Quality
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10. Communication Problem
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11. 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.
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12. The Traditional Approach
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13. 1.2: Major Principles of System Engineering
Methodology
Descriptions
Main descriptions
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14. 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.
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15. The Role of Methodology
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16. 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.
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17. Descriptions Symbolic representations of the subject matters
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18. Main Descriptions (I)
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19. Main Descriptions (II)
Why the system is needed
Requirements specification
What its functionality should be
Functional design
How it should be implemented
Implementation design
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20. 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
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21. Non-Functional Requirements
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22. 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
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23. 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
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24. Process Quality
The conformance between the requirement specification and the system.
Process quality vs system quality
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25. Quality Assurance
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26. 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.
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27. 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.
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28. 1.3: Managing the System Evolution
Reference model (waterfall model)
Documents
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29. Waterfall Model
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30. 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
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31. Milestones and Baselines
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32. Maintenance
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33. Activity Model
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34. Documents
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