Life cycle of an information system. System life cycle views

From the working curriculum:

Topic 2. Standards and regulatory guidelines for systems and software engineering.

ISO/IEC 15288 "Systems engineering - systems life cycle processes".

GOST 34: Set of standards for automated systems.

Key ideas of systems engineering: systems approach, system life cycle, requirements engineering, architectural design, process approach, project approach.

2.1. ISO 15288 "Systems engineering - systems life cycle processes".

2.2. Life cycle systems.

2.3. System life cycle views.

2.4. Life cycle of an information system

2.5. Life cycle models

2.6. Choosing a Life Cycle Model

2.1. ISO 15288 systems engineering - systems life cycle processes.

Systems engineering is used to solve problems associated with the increasing complexity of man-made systems. The ISO 15288 standard, which describes systems engineering practices, requires a description of the system life cycle and its practices. Such a description is required for the successful progression of the system through its life cycle. But the standard does not specify the methods by which such a description is required to be created.

Objectives of the standard:

To enable organizations (external and internal contractors) to agree on the combination of ideas, processes of design, creation, operation and decommissioning of a wide variety of man-made systems - from toothpicks to nuclear power plants, from standardization systems to corporations

Implement a number of key systems engineering ideas into the organization’s practice:

• systematic approach

  life cycle

  requirements engineering

  architectural design

  process approach

  project approach

  contract culture

IsTOriyacreation

Joint development of ISO and IEC, active participation of INCOSE

Start of work in 1996, versions in 2002, 2005 (GOST R ISO/IEC 15288-2005), 2008

Designed to harmonize the so-called “swamp of standards” of systems engineering (numerous standards adopted by various military departments, states, industry standardization organizations)

Experts from various fields were involved in the development of the standard: systems engineering, programming, quality management, human resources, security, etc. Practical experience in creating systems in government, commercial, military and academic organizations was taken into account. The standard is applicable to a wide class of systems, but its main purpose is to support the creation of computerized systems.

2.2. System life cycle

Russian abbreviation: J C

English abbreviation: L.C. (LifeCycle)

Russian: "life cycle". The English life cycle in technology previously meant and was translated as “service life”, and sometimes even “service life until the first major overhaul”. "Life cycle" is relative new translation. Sometimes “cycle” is translated as “period”, but this translation has not been established (although it is more accurate in this case: the “life period” of the system). The word “cycle” should not be confusing - there is nothing cyclical in the life cycle. The word "cycle" has the sense of "typicality", suggesting that the same thing happens to other systems.

Formally: the life cycle is a change in the states of a system (evolution of the system) during the period of time from conception to the termination of its existence.

The system and the life cycle are twin brothers. We say system - we mean the life cycle, we say life cycle - we mean the system.

Definitions.

Definition of the ISO/IEC 15288:2008 standard (Definition: life cycle -- evolution of a system, product, service, project or other human-made entity from conception through retirement (ISO 15288, 4.11):

life cycle (life cycle) is the evolution of a system, product, service, project or other man-made object from conception to termination of use.

Definition of the ISO 15704 standard (Industrial automation systems - Requirements for enterprise-reference architectures and methodologies)

life cycle (Life cycle) is a finite set of main phases and steps that a system goes through throughout its entire history of existence.

Each system, regardless of its type and scale, goes through its entire life cycle according to some description. The progression of the system through parts of this description is the life cycle of the system. The life cycle description is thus - this is a conceptual segmentation by stages, facilitating the planning, deployment, operation and support of the target system.

Stages (Table 2.1) represent the largest periods of the life cycle associated with a system and correspond to states of the system description or implementation of the system as a set of products or services. The stages describe the main milestones of a system's progress and success throughout its life cycle. Such segments provide orderly progression of the system through established resource allocation revisions, which reduces risks and ensures satisfactory progression. The main reason for using life cycle descriptions is the need to make decisions based on certain criteria before moving the system to the next stage.

Table 2.1

The life cycle is not a time period of existence, but a process of sequential changes in state, determined by the type of impacts produced (R 50-605-80-93).

The term “system life cycle” usually refers to the evolution new system in the form of several stages, including such important stages as concept, development, production, operation and final decommissioning:70.

History of the life cycle concept

The life cycle concept originated in late XIX V. as a complex of ideas, including the ideas of heredity and development at the level of individuals and organisms, as well as adaptation, survival and extinction at the level of individual species and entire populations of living organisms.

Typical system life cycle models

There is no single life cycle model that will satisfy the requirements of every possible task. Various organizations Standardization agencies, government agencies, and engineering societies publish their own models and technologies that can be used to construct the model. Thus, it is inappropriate to claim the existence of a single possible algorithm for constructing a life cycle model.

Some systems engineering experts suggest considering a system life cycle model based on the following three sources: the Department of Defense (DoD) logistics management model (DoD 5000.2), the ISO/IEC 15288 model, and the National Society of Professional Engineers (NSPE):71.

Typical life cycle model according to ISO/IEC 15288

According to the standard, life cycle processes and activities are defined, appropriately configured and used during a life cycle stage to fully satisfy the goals and results of that stage. Different organizations may be involved in different stages of the life cycle. There is no single universal model of system life cycles. Certain stages of the life cycle may be absent or present depending on each specific case of system development:34.

The standard gave the following life cycle stages as examples:

1. The idea.
2. Development.
3. Production.
4. Application.
5. Application support.
6. Discontinuation and write-off.

There are no examples of life cycle stages in the 2008 version of the standard (ISO/IEC 15288:2008).

Typical life cycle model according to the US Department of Defense

To manage the risks of using advanced technologies and minimize costly technical or management errors, the US Department of Defense has developed guidance that contains all the necessary principles for system development. These principles are included in a special list of directives - DoD 5000.

The life cycle model of a logistics management system according to the US Department of Defense consists of five stages:71:

1. Analysis.
2. Technology development.
3. Engineering and production development.
4. Production and deployment.
5. Operation and support.

National Society of Professional Engineers (NSPE) Generic System Life Cycle Model

This model developmentally adapted commercial systems. This model mainly focuses on the development of new products, usually the result of technological progress. The NSPE model provides an alternative view of the DoD version model. The life cycle according to the NSPE model is divided into six stages:72:

1. Concept.
2. Technical implementation.
3. Development.
4. Commercial validation and production preparation.
5. Full-scale production.
6. End product support.

Typical product life cycle model according to R 50-605-80-93

The guidance document R 50-605-80-93 carefully studies the life cycle of an industrial product, including - military equipment.

For industrial products for civilian use, the following stages are proposed:

1. Research and design.
2. Manufacturing.
3. Appeal and implementation.
4. Operation or consumption.

Within the life cycle of industrial products for civilian use, it is proposed to consider 73 types of work and 23 types of stakeholders (“work participants” in the terminology of the document).

For industrial products for military purposes, the following stages are proposed:

1. Research and justification of development.
2. Development.
3. Production.
4. Exploitation.
5. Major renovation.

Within the life cycle of military industrial products, it is proposed to consider 25 types of work and 7 types of stakeholders (work participants).

Typical software life cycle model

The stages of the system life cycle and their component phases, presented in the figure “System Life Cycle Model,” apply to most complex systems, including those that contain software with significant volume functionality at the component level. In software-intensive systems in which software performs almost all functions (such as in modern financial systems, airline reservation systems, global network Internet, etc.), as a rule, life cycles are similar in content, but are often complicated by iterative processes and prototyping: 72-73.

Main stages of the system life cycle (Kossiakoff, Sweet, Seymour, Biemer)

As shown in the figure "System Life Cycle Model", the system life cycle model contains 3 stages. The first 2 stages are during development, and the third stage covers post-development. These stages show more general transitions from state to state in the life cycle of a system, and also show changes in the type and scope of activities involved in systems engineering. The stages are:73:

• concept development stage;
• technical development stage;
• post-development stage.

Concept development stage

The purpose of the concept development stage is to assess new possibilities in the field of application of the system, develop preliminary system requirements and possible design solutions. The conceptual design development stage begins with the realization of the need to create a new system or modify an existing one. The stage includes the beginning of factual research, a planning period, and the economic, technical, strategic and market bases of future actions are assessed. A dialogue is taking place between stakeholders and developers.

Main goals of the concept development stage:74:

1. Conduct research to determine what is needed for the new system, as well as the technical and economic feasibility of the system.
2. Explore potential system concepts and formulate and validate a set of system performance requirements.
3. Select the most attractive system concept and define it functional characteristics, as well as develop a detailed plan for the subsequent stages of design, production and operational deployment of the system.
4. Develop any new technology suitable for the chosen system concept and validate its ability to meet the needs.

Technical development stage

The technical development stage involves the process of designing a system to implement the functions formulated in the system concept into a physical embodiment that can be supported and successfully operated in its operating environment. Systems engineering is primarily concerned with guiding development and design, managing interfaces, developing test plans, and determining how discrepancies in the performance of a system not verified during testing and evaluation should be properly corrected. The bulk of engineering activities are carried out at this stage.

The main objectives of the technical development stage are:74:

1. Perform technical development of a system prototype that meets performance, reliability, maintainability, and safety requirements.
2. Design a system suitable for use and demonstrate its operational suitability.

Post-development stage

The post-development stage consists of activities outside the system development period, but still requires significant support from systems engineers, especially when unexpected problems are encountered that require prompt resolution. In addition, advances in technology often require internal service system upgrades, which can be as dependent on systems engineering as the concept and technical development stages.

1. IS life cycle and its structure. 2

1.1 Stages of the IS life cycle.. 3

1.2 IS life cycle standards.. 4

2. Life cycle models. 6

2.1 Types of IS life cycle models.. 6

2.2 Advantages and disadvantages of IS life cycle models.. 8

3. IS life cycle processes.................................................... .................. eleven

3.1 Basic life cycle processes. eleven

3.2 Helper Processes life cycle. 13

3.3 Organizational processes.. 14

List of used literature... 16

The life cycle of an information system is a period of time that begins from the moment a decision is made on the need to create an information system and ends at the moment it is completely taken out of service.

The concept of life cycle is one of the basic concepts of design methodology information systems.

The methodology for designing information systems describes the process of creating and maintaining systems in the form of an IS life cycle (LC), presenting it as a certain sequence of stages and processes performed on them. For each stage, the composition and sequence of work performed, the results obtained, methods and means necessary to complete the work, the roles and responsibilities of the participants, etc. are determined. Such a formal description of the life cycle of an information system makes it possible to plan and organize the process of collective development and ensure management of this process.

The full life cycle of an information system usually includes strategic planning, analysis, design, implementation, implementation and operation. IN general case the life cycle can in turn be divided into a number of stages. In principle, this division into stages is quite arbitrary. We will consider one of the options for such a division, offered by Rational Software Corporation, one of the leading companies in the software market for information systems development tools (among which the universal CASE tool Rational Rose is deservedly very popular).

1.1 Stages of the IP life cycle

Stage - part of the process of creating an IP, limited by a certain time frame and ending with the release of a specific product (models, software components, documentation), determined by the requirements specified for this stage. The relationship between processes and stages is also determined by the IS life cycle model used.

According to the methodology proposed by Rational Software, the life cycle of an information system is divided into four stages.

The boundaries of each stage are defined by certain points in time at which certain critical decisions must be made and, therefore, certain key goals must be achieved.

1) Initial stage

At the initial stage, the scope of the system is established and the boundary conditions are determined. To do this, it is necessary to identify all external objects with which the developed system must interact, and determine the nature of this interaction on high level. At the initial stage, all the functionality of the system is identified and the most significant of them are described.

2) Clarification stage

At the clarification stage, an analysis of the application area is carried out, and the architectural basis of the information system is developed.

When making any decisions regarding system architecture, it is necessary to take into account the system being developed as a whole. This means that it is necessary to describe most of the functionality of the system and take into account the relationships between its individual components.

At the end of the clarification stage, an analysis of architectural solutions and ways to eliminate the main risk factors in the project is carried out.

3) Construction stage

At the design stage, a finished product is developed, ready for delivery to the user.

At the end of this stage, the performance of the developed software is determined.

4) Commissioning stage

At the commissioning stage, the developed software is transferred to users. When operating a developed system in real conditions, various types of problems often arise that require additional work to make adjustments to the developed product. This is usually associated with the detection of errors and shortcomings.

At the end of the commissioning stage, it is necessary to determine whether the development objectives have been achieved or not.

1.2 IP life cycle standards

Modern networks are developed on the basis of standards, which makes it possible to ensure, firstly, their high efficiency and, secondly, the possibility of their interaction with each other.

Among the most well-known standards are the following:

GOST 34.601-90 - applies to automated systems and establishes the stages and stages of their creation. In addition, the standard contains a description of the content of work at each stage. The stages and stages of work enshrined in the standard are more consistent with the cascade life cycle model.

ISO/IEC 12207 (International Organization of Standardization / International Electrotechnical Commission) 1995 - standard for processes and life cycle organization. Applies to all types of custom software. The standard does not contain descriptions of phases, stages and stages.

The Rational Unified Process (RUP) offers an iterative development model that includes four phases: start, explore, build, and implement. Each phase can be broken down into stages (iterations) that result in a version being released for internal or external use. Progress through four main phases is called a development cycle, each cycle ending with the generation of a version of the system. If work on the project does not stop after this, then the resulting product continues to develop and again goes through the same phases. The essence of work within RUP is the creation and maintenance of UML-based models.

Microsoft Solution Framework (MSF) is similar to RUP, it also includes four phases: analysis, design, development, stabilization, it is iterative, and involves the use of object-oriented modeling. MSF, compared to RUP, is more focused on the development of business applications.

Extreme Programming (XP). Extreme programming (the newest among the methodologies under consideration) was formed in 1996. The basis of the methodology teamwork, effective communication between the customer and the contractor throughout the entire IP development project, and the development is carried out using consistent highly refined prototypes.

2. Life cycle models

An IS life cycle model is a structure that defines the sequence of execution and relationships between processes, actions and tasks throughout the life cycle. The life cycle model depends on the specifics, scale and complexity of the project and the specific conditions in which the system is created and operates.

The IS life cycle model includes:

results of work at each stage;

key events - points of completion of work and decision-making.

The life cycle model reflects various states systems, starting from the moment the need for this information system arises and ending with the moment of its complete obsolescence.

2.1 Types of IS life cycle models

The following life cycle models are currently known and used:

The cascade model (Fig. 2.1) provides for the sequential implementation of all stages of the project in a strictly fixed order. The transition to the next stage means the complete completion of work at the previous stage.

Staged model with intermediate control (Fig. 2.2). IS development is carried out in iterations with feedback loops between stages. Interstage adjustments make it possible to take into account the actual mutual influence of development results at various stages; The lifetime of each stage extends over the entire development period.

Spiral model (Fig. 2.3). At each turn of the spiral, the next version of the product is created, the requirements of the project are specified, its quality is determined, and the work of the next turn is planned. Special attention is given initial stages development - analysis and design, where the feasibility of certain technical solutions is checked and justified through the creation of prototypes (layout).

Rice. 2.1. Cascade model of IS life cycle

Rice. 2.2. Stepwise model with intermediate control

Rice. 2.3. Spiral model of IS life cycle

In practice, two main life cycle models are most widely used:

cascade model (typical for the period 1970-1985);

spiral model (typical for the period after 1986).

2.2 Advantages and disadvantages of IP life cycle models

In early projects of fairly simple IS, each application was a single, functionally and informationally independent block. The cascade method has proven to be effective for developing this type of application. Each stage was completed after complete completion and documentation of all required work.

(MSF). Includes 4 phases: analysis, design, development, stabilization, involves the use of object-oriented modeling.

Standard GOST 34 .601-90

ISO/IEC 12207/ standard and its application

The ISO/IEC 12207:1995 standard “Information Technology - Software Life Cycle Processes” is the main regulatory document regulating the composition of IS life cycle processes. It defines a life cycle structure containing the processes, activities and tasks that must be completed during the creation of an IS.

Each process is divided into a set of actions, each action into a set of tasks. Each process, activity, or task is initiated and executed by another process as needed, and there are no predetermined execution sequences. The connections between the input data are preserved.

IS life cycle processes

• Basic:
  • Acquisition (actions and tasks of the customer purchasing the IP)
  • Delivery (actions and tasks of the supplier who supplies the customer with a software product or service)
  • Development (actions and tasks performed by the developer: software creation, design and operational documentation, preparation of test and educational materials etc.)
  • Operation (actions and tasks of the operator - the organization operating the system)
  • Maintenance (actions and tasks performed by the accompanying organization, that is, the support service). Support - making changes to software in order to correct errors, improve productivity, or adapt to changed operating conditions or requirements.
• Auxiliary
  • Documentation (formalized description of information created during the IS life cycle)
  • Configuration management (application of administrative and technical procedures throughout the life cycle of the IS to determine the state of IS components and manage its modifications).
  • Quality assurance (providing guarantees that the information system and its life cycle processes comply with specified requirements and approved plans)
  • Verification (determining what software products, which are the results of some action, fully satisfy the requirements or conditions determined by previous actions)
  • Certification (determining the completeness of compliance of the specified requirements and the created system with their specific functional purpose)
  • Joint assessment (assessment of the status of work on the project: control of planning and management of resources, personnel, equipment, tools)
  • Audit (determining compliance with requirements, plans and contract terms)
  • Problem resolution (analysis and resolution of problems, regardless of their origin or source, that are discovered during development, operation, maintenance or other processes)
• Organizational
  • Control (actions and tasks that can be performed by any party managing its processes)
  • Creation of infrastructure (selection and maintenance of technology, standards and tools, selection and installation of hardware and software used for development, operation or maintenance of software)
  • Improvement (assessment, measurement, control and improvement of life cycle processes)
  • Training (initial training and subsequent ongoing staff development)

Each process includes a number of actions. For example, the acquisition process covers the following activities:

1. Initiation of acquisition
2. Preparation of bid proposals
3. Preparation and adjustment of the contract
4. Supervision of supplier activities
5. Acceptance and completion of work

Each activity includes a number of tasks. For example, the preparation of bid proposals should include:

1. Formation of system requirements
2. Generating a list of software products
3. Establishing terms and agreements
4. Description of technical limitations (system operating environment, etc.)

Stages of the IS life cycle, relationships between processes and stages

IP life cycle model- a structure that determines the sequence of execution and relationships between processes, actions and tasks throughout the life cycle. The life cycle model depends on the specifics, scale and complexity of the project and the specific conditions in which the system is created and operates.

IP life cycle models

Cascade model

Cascade life cycle model (“waterfall model”, English. waterfall model) was proposed in 1970 by Winston Royce. It provides for the sequential implementation of all stages of the project in a strictly fixed order. The transition to the next stage means the complete completion of work at the previous stage. The requirements defined at the stage of requirements formation are strictly documented in the form terms of reference and are recorded for the entire development of the project. Each stage culminates in the release of a complete set of documentation sufficient to allow development to be continued by another development team.

Project stages according to the waterfall model:

1. Formation of requirements
2. Design
3. Implementation
4. Testing
5. Commissioning
6. Operation and maintenance

Spiral model

Iterative model

The natural development of the cascade and spiral models led to their convergence and the emergence of a modern iterative approach, which represents a rational combination of these models. Various variants of the iterative approach are implemented in most modern technologies and methods: RUP, MSF, .

Literature

• Bratishchenko V.V. Information systems design. - Irkutsk: Publishing house BGUEP, 2004. - 84 p.
• Vendrov A.M. Design of software for economic information systems. - M.: Finance and Statistics, 2000.
• Grekul V.I., Denishchenko G.N., Korovkina N.L. Information systems design. - M.: Internet University of Information Technologies - INTUIT.ru, 2005.
• Mishenin A.I. Theory of economic information systems. - M.: Finance and Statistics, 2000. - 240 p.

Notes

Wikimedia Foundation. 2010.

• "Studies in Contemporary Russian History"
• Drobnitsa

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The life cycle is not a time period of existence, but a process of sequential changes in state, determined by the type of impacts produced (R 50-605-80-93).

The term "system life cycle" usually refers to the evolution of a new system in the form of several stages, including such important stages as concept, development, production, operation and final decommissioning. :70

Encyclopedic YouTube

1 / 5

Video 22. Software life cycle. Stages of software development. Classic model software development

"Life cycle of a system or project" - training No. 2.

Product life cycle.mp4

Defect life cycle

Life cycle of an organization

Subtitles

History of the concept

The concept of the life cycle arose at the end of the 19th century. as a complex of ideas, including the ideas of heredity and development at the level of individuals and organisms, as well as adaptation, survival and extinction at the level of individual species and entire populations of living organisms.

Typical system life cycle models

There is no single life cycle model that will satisfy the requirements of every possible task. Various standards organizations, government agencies, and engineering societies publish their own models and technologies that can be used to construct the model. Thus, it is inappropriate to assert the existence of any one possible algorithm for constructing a model. However, any life cycle model can be divided into a series of main steps that will reflect individual important stages.

Some systems engineering experts suggest looking at a system life cycle model based on three sources: the Department of Defense (DoD) logistics management model (DoD 5000.2), the ISO/IEC 15288 model, and the National Society of Professional Engineers (NSPE) model. ). :71

Typical life cycle model according to ISO/IEC 15288

According to the standard, life cycle processes and activities are defined, appropriately configured and used during a life cycle stage to fully satisfy the goals and results of that stage. Different organizations may be involved in different stages of the life cycle. There is no single universal model of system life cycles. Certain stages of the life cycle may be absent or present depending on each specific case of system development. :34

The standard gave the following life cycle stages as examples:

1. Concept stage.
2. Development stage.
3. Production stage.
4. Application stage.
5. Application support stage.
6. Stage of discontinuation of use and write-off.

There are no examples of life cycle stages in the 2008 version of the standard (ISO/IEC 15288:2008).

Typical life cycle model according to the US Department of Defense

To manage the risks of using advanced technologies and minimize costly technical or management errors, the US Department of Defense has developed guidance that contains all the necessary principles for system development. These principles are included in a special list of directives - DoD 5000.

The life cycle model of a logistics management system according to the US Department of Defense consists of five stages:71:

• analysis;
• technology development;
• engineering and production development;
• production and deployment;
• operation and support.

National Society of Professional Engineers (NSPE) Generic System Life Cycle Model

This model is adapted for the development of commercial systems. This model mainly focuses on the development of new products, usually the result of technological progress. The NSPE model provides an alternative view of the DoD version model. The life cycle according to the NSPE model is divided into six stages:72:

• concept;
• technical implementation;
• development;
• commercial validation and production preparation;
• full-scale production;
• end product support.

Product life cycle model according to R 50-605-80-93

The guidance document R 50-605-80-93 carefully studies the life cycle of an industrial product, including military equipment.

For industrial products for civilian use, the following stages are proposed:

• research and design;
• manufacturing;
• circulation and implementation;
• exploitation or consumption.

Within the life cycle of industrial products for civilian use, it is proposed to consider 73 types of work and 23 types of stakeholders (“work participants” in the terminology of the document).

For industrial products for military purposes, the following stages are proposed:

• research and development justification;
• development;
• production;
• exploitation;
• major renovation.

Within the life cycle of military industrial products, it is proposed to consider 25 types of work and 7 types of stakeholders (work participants).

Typical software life cycle model

The system life cycle stages and their component phases, presented in the figure "System Life Cycle Model", apply to most complex systems, including those that contain software with a significant amount of functionality at the component level. In software-intensive systems in which software performs almost all functions (such as in modern financial systems, airline ticket reservation systems, the global Internet, etc.), as a rule, life cycles are similar in content, but are often complicated by iteration processes and prototyping. :72-73

Main stages of the system life cycle (Kossiakoff, Sweet, Seymour, Biemer)

As shown in the figure "System Life Cycle Model", the system life cycle model contains 3 stages. The first 2 stages are during development, and the third stage covers post-development. These stages show more general transitions from state to state in the life cycle of a system, and also show changes in the type and scope of activities involved in systems engineering. The stages are:73:

• concept development stage;
• technical development stage;
• post-development stage.

Concept development stage

The purpose of the concept development stage is to evaluate new possibilities in the field of application of the system, develop preliminary system requirements and possible design solutions. The conceptual design development stage begins with the realization of the need to create a new system or modify an existing one. The stage includes the beginning of factual research, a planning period, and the economic, technical, strategic and market bases of future actions are assessed. A dialogue is taking place between stakeholders and developers. :

Main goals of the concept development stage: :74

1. Conduct research to determine what is needed for the new system, as well as the technical and economic feasibility of the system.
2. Explore potential system concepts and formulate and validate a set of system performance requirements.
3. Select the most attractive system concept, determine its functional characteristics, and develop a detailed plan for the subsequent stages of design, production and operational deployment of the system.
4. Develop any new technology suitable for the selected system concept and validate its ability to meet the needs.

Technical development stage

The technical development stage involves the process of designing a system to implement the functions formulated in the system concept into a physical embodiment that can be supported and successfully operated in its operating environment. Systems engineering is primarily concerned with guiding development and design, managing interfaces, developing test plans, and determining how discrepancies in the performance of a system not verified during testing and evaluation should be properly corrected. The bulk of engineering activities are carried out at this stage.

The main objectives of the technical development stage are:74:

1. Perform technical development of a system prototype that meets performance, reliability, maintainability, and safety requirements.
2. Design a system suitable for use and demonstrate its operational suitability.

Post-development stage

The post-development stage consists of activities outside the system development period, but still requires significant support from systems engineers, especially when unexpected problems are encountered that require prompt resolution. In addition, advances in technology often require internal service system upgrades, which can be as dependent on systems engineering as the concept and technical development stages.

The post-development stage of a new system begins after a successful operation of testing and evaluating the system (acceptance testing), release into production and subsequent operational use. Until major development is completed, systems engineering will continue to play a major supporting role