Systems Engineering and Management

This part of the SEBoK focuses on the general knowledge of how systems are engineered. It builds on Part 2, which discusses what systems are. Part 3 provides a basis for the engineering of product systems , the engineering of service systems , the engineering of an enterprise system as well as the engineering of systems of systems as described in Part 4. Part 3 defines systems engineering and also provides an overview of the common life cycle models uses in systems engineering. The commonly-used systems engineering processes are also described, with references to common methods, tools, and techniques used within these processes. Finally, the management aspects of systems engineering are discussed.

It is important to note that Part 3 provides an overview of how systems are engineered in a generic sense. Part 4 provides specific information on how the principles discussed in Part 3 are applied differently depending on the type of system (product, service, or enterprise) being engineered. Part 5 then explains how an organization may approach utilizing these principles in a holistic manner. Part 6 provides references to other/related disciplines which may be utilized in the various systems engineering processes described in Part 3, but which do not fall under the umbrella of systems engineering.

Knowledge Areas in Part 3

Each part of the SEBoK is divided into knowledge areas (KAs): groupings of information with a related theme. Part 3 contains the following knowledge areas:

Systems Engineering Definition

There is not a community consensus on the definition of "systems engineering"; the term has many different connotations in many different domains. One of the more commonly recognized definitions in the field is likely that of the International Council on Systems Engineering (INCOSE):

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. (INCOSE 2010, 1)

This definition is frequently referenced throughout the SEBoK. Systems engineering is the application of a combination of traditional engineering and holistic systems thinking, working with domain engineering, human sciences, management and commercial disciplines, to support the engineering of one or more systems of interest (SoI). It may also be an interdisciplinary approach governing the total technical and managerial effort required to transform a set of customer needs, expectations, and constraints into a solution and to support that solution throughout its life. Each of these perspectives is valuable for gaining a holistic view of systems engineering.

Generic Systems Engineering Paradigm

Figure 1 identifies the general goal of any systems engineering effort. That is the understanding of stakeholder value, the selection of a specific need; the transformation of that need into a system product or service that provides for the need; and the use of that product or service to provide the stakeholder value. This paradigm has been developed according to the principles of a systems approach as discussed in Part 2. This paradigm was used to establish a basis for the KAs in Part 3 and Part 4 of the SEBoK.

Figure 1. Generic Systems Engineering Paradigm (Figure Developed for BKCASE).

On the left hand side of Figure 1, there are three systems of interest (soi) identified in the form of a system breakdown structure . SoI 1 is decomposed into its elements, which in this case are systems as well (SoI 2 and SoI 3). These two systems are composed of system elements , which are not further refined.

On the right-hand side of the figure, each SoI has a corresponding life cycle model composed of stages that are populated with processes. These processes are used to define the work to be performed. Note that some of the requirements defined to meet the need are distributed in the early stages of the life cycle for SoI 1, and some to the life cycles of SoI 2 or SoI 3. This decomposition of the system illustrates the fundamental concept of recursion , as defined in the ISO/IEC 15288 standard. That standard is reapplied for each SoI. It is important to note that stakeholder requirements may be allocated to different system elements, which may be integrated in different life cycle stages of any of the three SoIs, but together they form a cohesive system. For example - SoI 1 could be an embedded system composed a hardware system (SoI 2) composed of a chasis and a motor, and a software system (SoI 3).

When performing systems engineering processes in stages, iteration between stages is often required, e.g., in successive refinement of the definition of the system or in providing an update or upgrade of an existing system. The work performed in the processes and stages can be performed in a concurrent manner within the life cycle of any of the systems of interest and concurrent amongst the multiple life cycles.

This paradigm provides a fundamental framework for understanding generic systems engineering (seen in Part 3) as well as for the application of systems engineering to the various types of systems described in Part 4.

Applying Iteration and Recursion to Systems Engineering in the Life Cycle

The concept of iteration is applied also for processes. Figure 2 below gives an example of iteration of three processes as defined in ISO/IEC 15288. The processes in this example are further discussed in the System Definition knowledge area.

Figure 2. Example of iterations of processes related to system definition (ISO/IEC 2003,p. 21, Figure 12) Source available at http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=33898

The complete definition of a SoI is generally achieved using decomposition layers and system elements . Figure 3 presents a fundamental schema of a system breakdown structure.

Figure 3. Hierarchical decomposition of a system-of-interest (ISO/IEC 2008) Source available at http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=43564

In each decomposition layer and for each system, the System Definition processes are applied recursively because the notion of system is recursive; the notions of SoI, system, and system element are based on the same concepts – see Part 2. Figure 4 shows an example of recursion of three processes as defined in ISO/IEC 15288.

Figure 4. Recursion of processes on layers (ISO/IEC 2003, p.20, Figure 11) Source available at http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=33898

Value of Ontology Concepts for Systems Engineering

Ontology is the set of entities presupposed by a theory (Collins English Dictionary). SE, and in particular system development, is based on concepts related to mathematics and proven practices. A SE ontology can be defined considering the following path.

SE provides engineers with an approach based on a set of concepts (i.e. stakeholder, requirement, function, scenario, system element, etc.) and generic processes. Each process is composed of a set of activities and tasks gathered logically around a theme or a purpose. A process describes “what to do” using the concepts. The implementation of the activities and tasks is supported by methods and modeling techniques, composed themselves of elementary tasks; they describe the “how to do”. The activities and tasks of SE are transformations of generic data using the predefined concepts. Those generic data are called entities, classes, or types. Each entity is characterized by specific attributes, and each attribute can get different values. All along their execution, the activities and tasks of processes, methods, and modeling techniques exchange instances of generic entities according to logical relationships. These relationships allow the engineer to link the entities between themselves (traceability) and to follow a logical sequence of the activities and the global progression (engineering management). Cardinality is associated with every relationship, expressing the minimum and maximum number of entities in order to make the relationship valid. Additional information may be found in Oliver, Kelliher, and Keegan (1997).

The set of SE entities and their relationships form an ontology also often called an engineering meta-model. Such an approach is used and defined in the standard (ISO 2007). The benefits of using an ontology are many. The ontology allows or forces:

the use of a standardized vocabulary, using the right names and avoiding using synonyms in the processes, methods, and modeling techniques;
reconciliation of the vocabulary used in different modeling techniques and methods;
the automatic appearance of traceability of requirements when implemented in databases, SE tools or workbenches, and also the quick identification of the impacts of modifications in the engineering data set;
checks of the consistency and completeness of engineering data, etc.

Readers are encouraged to read the "ontology" discussions embedded within articles in Part 3. Review comments regarding ontology will be particularly helpful in moving to version 1.0.

Mapping of Topics to ISO/IEC 15288, System Life Cycle Processes

Note: To facilitate readers' understanding of the standard ISO/IEC. 2008, Figure 5 below shows the relative position of the Technical Knowledge Areas (KA) of this SEBoK with respect to the processes as stated in the standard.

Figure 5. Mapping of technical topics of Knowledge Areas of SEBoK with ISO/IEC 15288 Technical Processes (Figure Developed for BKCASE)

References

Works Cited

Collins English Dictionary, s.v. "Ontology." 2011.

INCOSE. 2011. Systems Engineering Handbook, version 3.2.1. San Diego, CA, USA: International Council on Systems Engineering (INCOSE).

ISO/IEC. 2003. Systems Engineering — A Guide for The Application of ISO/IEC 15288 System Life Cycle Processes. Geneva, Switzerland: International Organization for Standardization (ISO)/International Electronical Commission (IEC), ISO/IEC 19760:2003 (E).

ISO/IEC 2008. Systems and Software Engineering -- System Life Cycle Processes. Geneva, Switzerland: International Organisation for Standardisation / International Electrotechnical Commissions / Institute for Electrical and Electronics Engineers. ISO/IEC/IEEE 15288:2008.

ISO. 2007. Systems Engineering and Design. Geneva, Switzerland: International Organization for Standardization (ISO). ISO 10303-AP233.

Oliver, D., T. Kelliher, and J. Keegan. 1997. Engineering Complex Systems with Models and Objects. New York, NY, USA: McGraw-Hill.