Explanatory note. Technical documentation Sample explanatory note to the technical specifications

Below is an example (sample) of a project document " Explanatory note to technical project to create an automated system", based on guidelines RD 50-34.698-90. This document is generated by an IT specialist at the stage technical design of information system.

As an example of the development of an information system, a project for introducing an information and analytical system was used "Corporate data warehouse".

The page below shows contents of the explanatory note of the technical project in accordance with GOST, within each section briefly The content requirements and the text of the filling example are given.(distinguished by a vertical line).

Sections of the explanatory note:

General provisions

Main technical solutions

Decisions on the structure of the system, subsystems, means and methods of communication for information exchange between system components

Solutions for interconnecting the speaker system with related systems and ensuring its compatibility

Decisions on operating modes, diagnosing system operation

Decisions on personnel and their work modes

Information on ensuring the consumer characteristics of the system specified in the technical specifications, which determine its quality

Composition of functions, sets of tasks implemented by the system

Composition and placement of technical equipment complexes

An example of an “Explanatory Note” (P2), developed for an automated measurement and information system commercial accounting electricity (AIIS KUE) according to the document. by i. Revision dated June 20, 2018.

Explanatory note (P2 according to GOST 34.201-89) of the automated measurement and information system for commercial electricity metering (AIIS KUE) (example)

Created 03/25/2014 11:48:18

Attention! Technical requirements wholesale electricity market (WEM), links to points of which are contained in examples of documents for automated measurement and information systems for commercial electricity metering (AIIS KUE), change quite often, but not by us, but by the administrator trading system(PBX). Please be understanding about this

All documents combat, which have passed many tests, including examinations at the Federal State Unitary Enterprise “All-Russian Research Institute of Standardization and Certification in Mechanical Engineering” (VNIIMASH) of ROSSTANDART, therefore there is no doubt.

For getting free an abbreviated version of any in the form of *.pdf is enough to click on the title page. The document will open in the browser with the option to. Full versions documents are paid, they can be obtained in format for a certain amount by using. Any document can be modified over a period of time to meet the specific requirements of the customer. Conditions are being discussed.

As a rule, the Explanatory Note is the most complex document on software, sometimes causing a lot of controversy and discussion around its content. Why does this happen?

Purpose of the explanatory note

We have already said that in software development this is one of the important stages. It should contain a description of your system taking into account the selected technologies, as GOST 34 requires of us. And the document Explanatory Note to the Technical Project, or, in short, PZ, is one of the main documents of this stage. And, I must say, most often it is the Explanatory Note that is the most complex document on software, sometimes causing a lot of controversy and discussion around its content.

Composition of a standard explanatory note

The explanatory note to the technical project includes sections such as:

– Introduction. This section provides the full name of the system and the topic of development, as well as a list of documents that served as the basis for the work on the project.

– Purpose and scope. It describes the goals and objectives that will be solved using the system, as well as the scope of its use.

– Specifications . This section is usually divided into subsections that describe: setting the task for creating a program; the mathematical apparatus used; software operation algorithm; structure of input and output data; composition of hardware and software. It is also necessary to provide calculations and analysis results to justify the choice of exactly those solutions mentioned in the document.

– Expected technical and economic indicators. The section assumes economic justification development taking into account its technical indicators.

– Sources used in development. The section is a list of documents, articles and publications that were referenced in the text.

Standards for explanatory notes

The composition of the sections is determined by GOST 19.404, however, the standard allows these sections to be combined, if necessary, and also to add new ones. In the case of using GOST series 34, a document should be developed in accordance with RD 50-34.698. However, the document must remain within the requirements common standards, such as, for example, GOST 19.105.

Cost of developing an explanatory note

How can you create a program document at the lowest cost that is most useful for your project, which:

– on the one hand, clearly and intelligibly presents all the necessary (and sometimes tedious) information, including complex technical details;

1. general provisions;
2. description of the activity;
3. basic technical solutions;
4. events on

[from clause 2.2.1 RD 50-34.698-90]

General provisions

In the “General Provisions” section they provide:

1. design and names of documents, their numbers and date, on the basis of which the NPP design is carried out;
2. list of those involved in the system, deadlines;
3. goals, purpose and AS;
4. confirmation of compliance of design solutions with current standards and fire and explosion safety, etc.;
5. information about those used in the design;
6. information about the best practices used in the development of the project;
7. the order of creation of the system and the volume of each.

[from clause 2.2.2 RD 50-34.698-90]

Description of the activity process

In the section “Description of the activity process” they reflect the composition of the procedures (), taking into account the interrelation and compatibility of processes and activities, form the organization of work in the plant [from clause 2.2.3 RD 50-34.698-90]

Main technical solutions

In the section “Main technical solutions” they give:

1. decisions on the structure of the system, means and methods of communication for information exchange between subsystems;
2. decisions on the interconnection of the system with related systems and its support;
3. solutions for system operation;
4. decisions on the number, qualifications and functions, modes of its operation, order of interaction;
5. information on ensuring the specified consumer characteristics of the system (subsystems) that define it;
6. composition of task complexes () implemented by the system (subsystem);
7. decisions on the complex, its placement on;
8. decisions on the composition of information, volume, methods, types of computer, and documents, sequence and other components;
9. decisions on the composition, languages ​​of activities, procedures and operations and methods of their implementation.

The section provides illustrations of other documents that may be included in accordance with GOST 34.201 [from clause 2.2.4 of RD 50-34.698-90]

Measures to prepare the automation object for putting the system into operation

In the section “Preparatory measures for putting the system into operation” the following is given:

1. measures to bring information into a form suitable for;
2. activities for training and testing the qualifications of personnel;
3. measures to create the necessary units and jobs;
4. measures to change the automation object;
5. other measures based on the specific features of the systems being created.

27.10.2016 09:57:23

This article discusses the technical project stage related to one of the stages of the system life cycle information security(SIB) - the “design” stage, which, in accordance with the domestic standard GOST 34.601-90, immediately follows the development of the Terms of Reference for the information security system.

1. Development of technical design documentation for NIB

Life cycle of an information security system (hereinafter - ISS) in general view consists of the following steps:

• analysis of requirements for information security systems;
• design;
• implementation;
• implementation;
• exploitation.

This article discusses the stage of the technical project, which belongs to the “design” stage and, in accordance with the domestic standard GOST 34.601-90, immediately follows the development of the Terms of Reference for the information security system.

1.1. Why develop documentation for NIB at all?

The answer to this question should be considered in two planes: in the plane of the owner information resources(for the protection of which the NIB is created) and in the plane of the immediate developer of the NIB.

For the owner of information resources, it is important to obtain the result in the form of a functioning information security system that reduces the risks of compromising restricted access information in the organization. The technical project in this case serves to develop the fundamental principles of the future system, namely, it includes a description of how the ISS will be built and function, what measures and means will ensure information protection, what are the possibilities for developing and improving the system. Upon completion of the development of a technical project for an information security system, the Customer receives a comprehensive set of documentation for the information security system, describing all technical nuances future system.

For the direct executor, at the stage of the technical project, it is necessary to lay down the most suitable NIB architecture, and also make right choice measures and means of protecting information in the organization. It is also important to ensure that the characteristics and properties of the system match technical specifications, or justify, with the participation and consent of the Customer, the adjustment of the requirements specified in the technical specifications in order to increase the efficiency of the created system.

Thus, as a result of the development of technical design documentation, the Customer will have answers to the following questions:

• what is the general architecture of the NIB;
• what measures and means will be used to implement information protection requirements;
• how the NIB will function;
• what changes in the organization necessary to increase the level of information security will follow as a result of the implementation of the ISS;
• will the Customer's requirements (business requirements) and the requirements of regulatory legal acts in the field of information security be taken into account when developing and implementing the information security system and, if so, how.

In the process of developing technical project documentation, the contractor will receive the following results:

• a basis for the transition to the next stages of building an ISS, namely the stages of working documentation and implementation;
• understanding of the architecture, technologies and tools used, the order of building the system;
• how the Customer’s requirements (business requirements) and regulatory documents in the field of information security are implemented for the system.

1.2. Review of approaches to developing technical project documentation

The development of a technical project for an information security system is most often carried out on the basis of relevant standards and guidance documents. And for government agencies their use is mandatory, but recommended for commercial ones. On practice commercial organizations also use state standards when developing technical project documentation for the following reasons:

• a repeatedly tested approach to creating information systems;
• thoughtful structure and content of documents;
• a set of documents sufficient for the development and description of almost any system.

To develop documentation for the technical project (TP) stage of the NIB, state standards and guidance documents of the 34 series are used:

• GOST 34.201-89 “Types, completeness and designation of documents when creating automated systems.” This standard specifies:
  • types and names of documents at the TP stage;
  • completeness of documentation;
  • accepted document designations;
  • rules for designating NIB and their parts.
• GOST 34.003-90 “Terms and definitions”;
• GOST 34.601-90 “Automated systems. Stages of creation." The standard specifies:
  • list of stages of work carried out at the technical stage;
  • detailed description of the work carried out at the technical stage;
  • list of organizations participating in the creation of the ISS;
• RD 50-34.698-90 “Automated systems. Requirements for the content of documents." This guidance document specifies the requirements for the content of documents at the TP stage.

It is important to understand that according to the 34 series of standards, technical design is a stage of creating a system, and not just a set of documents. In practice, this stage is often combined with the preliminary design stage, which serves to develop several preliminary solutions and justify the most suitable one. Such a combination is allowed by the standard, but it must be taken into account that this does not negate the need to achieve the goals of the preliminary design stage.

Most often, the preliminary design stage is developed in the case when the requirements of the technical specifications for the system can be implemented in several fundamentally different ways, and also when among these methods there are no clearly preferable ones.

However, it is worth noting that the above standards are too general and mainly implement design and general structural functions. To develop the substantive part of the technical project stage documents, designers use information from the following sources:

Current regulatory documents (RLA) regulating the requirements for the protection of certain restricted access information. These regulatory legal acts provide requirements for measures to protect information in information systems, the nuances of implementing these measures and additional strengthening measures are described. Among the current legal acts are the following:

• Order of the FSTEC of Russia dated February 18, 2013 No. 21 “On approval of the composition and content of organizational and technical measures to ensure the security of personal data during their processing in personal data information systems”;
• Order of the FSTEC of Russia dated February 11, 2013 No. 17 “On approval of requirements for the protection of information that does not constitute a state secret contained in state information systems”
• Order of the FSTEC of Russia dated March 14, 2014 No. 31 “On approval of requirements for ensuring the protection of information in automated systems production and technological processes at critical facilities, potentially dangerous objects, as well as objects that pose an increased danger to human life and health and to the environment;
• methodological document “Measures for protecting information in state information systems”, approved by the FSTEC of Russia on February 11, 2014.

Requirements for the protection of restricted access information and lists of protective measures vary for information systems of different levels/classes of security. If the information in the organization is not protected in accordance with federal laws RF (for example, official secret), then the owner of this information can use the approaches proposed in these regulatory legal acts for building a corporate ISS.

Russian and foreign standards describing various approaches to ways of implementing the stages of the life cycle of building an ISS, including the technical design stage:

• series of state standards GOST R ISO/IEC 2700X, identical international standards ISO/IEC 2700X. These standards describe process approach PDCA (Plan, Do, Check, Act) for the implementation of the life cycle of the information security management system, which is an integral part of the ISS;
• NIST SP 800-64 is a US National Institute of Standards and Technology standard that describes the information systems development life cycle;
• NIST SP 800-37 is a US National Institute of Standards and Technology standard that provides guidance for integrating risk management into the information systems development life cycle.

Manufacturer's operational documentation for information security equipment and auxiliary equipment. These documents contain comprehensive technical information about the tools used in the construction of information security systems, including those directly related to the implementation of information security measures not related to, for example, servers, data storage systems, virtualization tools and others. The general set of such documents varies from manufacturer to manufacturer and depends, among other things, on the implementation of a particular tool (hardware/software). Below is standard set operational documentation for information security tools, used to develop documents at the technical project stage:

• general description (datasheet);
• administrator's guide (may include local and centralized management guide);
• user guide;
• Quick Installation and Deployment Guide (for hardware information protection systems);
• operator's manual;
• Guidance for deployment in virtual infrastructure (for software information protection systems);

General information about existing SIS architectures, best practices in terms of building ISS, guidelines for security and integration of information security systems with each other, information about problems in the interaction of certain information security systems. Examples of such information may include the following documents:

• guides on information security system architectures, for example: Defense-in-Depth, Cisco SAFE, Check Point SDP and others;
• best practices in the field of information security, for example, available at these links (https://www.sans.org/reading-room/whitepapers/bestprac/, http://csrc.nist.gov/publications/nistpubs/800-14 /800-14.pdf). These documents are most often presented on English language, however, everyone has their own best practices for implementing security measures Russian manufacturer Information security information can be provided upon request;
• security guidelines for information security and operating environments. An example is the “Security” section on the official Microsoft portal (https://technet.microsoft.com/ru-ru/library/dd637672.aspx).

1.3. Development of a technical project for NIB in accordance with GOST 34

The development of documents at the technical project stage for ISS is most often carried out by integrators of these services and is implemented mainly in accordance with the following plan:

Determining the list of documents to be developed - this information is indicated in the technical specifications for the ISS. In some cases, the document developer, in agreement with the Customer, may expand or reduce this list, if this possibility is provided for in the technical specifications;

Development of document templates for the TP stage - the structure is used in accordance with RD 50-34.698-90 and GOST 2.106 (for some documents), formatted in accordance with GOST 2.105-95;

Development of the substantive part of documents. Requirements for the system are established in the technical specifications for the NIB. In accordance with these requirements, a list of protective technical and organizational measures required for implementation in the system is determined. Protection measures can be determined in the relevant regulations (depending on the type of information being protected), corporate standards and information security policies, as well as based on the presence of current security threats identified during the development of the organization's threat model. Based on the list of protection measures, the ISS developer selects appropriate information security means and develops the functional structure of the information security system (subsystems, components). Further, the technical design documents describe the practical implementation of protection measures based on the selected security protection or organizational measures in the organization's infrastructure.

Coordination of the developed documentation and the solutions presented in it with the Customer of the system.

When developing technical project documentation, most often it is not necessary to develop a complete list of documents specified in GOST 34.201-89, since this standard is outdated and some of the documents do not take into account the development trends and technologies of modern information systems. The minimum set of documents required to describe the information security system is as follows:

• technical design statement;
• explanatory note to the technical project;
• functional structure diagram;
• structural diagram of the complex technical means;
• organizational structure diagram;
• list of purchased items.

At the Customer’s request or in the event that the ISS is a complex multi-component system, the following documents can also be additionally developed:

• automation scheme;
• description of automated functions;
• description of the information support of the system;
• description of the complex of technical means;
• software description;
• description of the organizational structure.

It should be noted that GOST 34.201-89 allows for an expansion of the range of documents at the TP stage, but in practice there are more than enough of these documents.

Technical design sheet

Designation: TP.

This document is intended to describe the list of documents developed at the technical project stage. The number of pages of each of the developed documents is also indicated.

Explanatory note to the technical project

Designation: P2.

This document is the main one for the TP stage and includes a description of the ISS architecture, technical and organizational measures, ISS functions, software and hardware systems, and other things. According to the standard, it consists of four main sections:

• general provisions;
• description of the activity process;
• basic technical solutions;
• measures to prepare the automation object for putting the system into operation.

Functional structure diagram

Designation: C2.

This document describes the logical structure of the ISS, namely:

• logical subsystems and components included in the ISS;
• functions implemented by means of subsystems and components;
• information connections between logical elements of the SIS and types of messages during exchange.

Structural diagram of a complex of technical means

Designation: C1.

This document includes a description of the following elements of the ISS:

• technical means as part of logical subsystems and components of information security systems;
• communication channels and exchange between technical means indicating transport protocols.

Organizational chart

Designation: C0.

This document describes organizational structure organizations in terms of ISS management, namely:

• divisions and responsible persons of the organization involved in the functioning of the ISS;
• functions performed and connections between departments and responsible persons.

List of purchased items

Designation: VP.

This document includes a list of all software and hardware, as well as licenses used to create an information security system. Developed in accordance with GOST 2.106.

Note. It is also worth noting here that the guidance document RD 50-34.698-90 allows for the addition of any document at the TP stage (the inclusion of sections and information different from those proposed), the merging of sections, as well as the exclusion of some individual sections. Decisions about this are made by the developer of documents at the TP stage and are based on the features of the created NIB.

1.4. Rules for developing documentation

• structural compliance state standards;
• strict compliance with the requirements of the technical specifications for the system;
• application of document templates (use of uniform styles, markup, fields, etc.);
• an individual approach and the simultaneous use of existing developments when filling out sections of documents.

Explanatory note to the technical project:

• document development is carried out in the environment Microsoft Word, after completion of development, it is recommended to convert the document to PDF format for convenience;
• terms and abbreviations must be consistent throughout all sections of the document;
• It is recommended to avoid obvious repetitions and unnecessary increase in the length of the document;
• technical solutions must be described in as much detail as possible, indicating:
  • architecture and technologies used;
  • locations of software and hardware in the organization’s infrastructure;
  • information security tools used with a description of their characteristics, implemented functions, information about certification;
  • basic settings of information security tools in terms of protection mechanisms, addressing, routing, interaction with related systems and tools, etc.;
  • controls, methods of access to them and places of their installation;
  • diagrams (structural, functional, organizational):
    • develop diagrams in Microsoft Visio;
    • after development, insert diagrams into the document using the “Paste Special” dialog in EMF format (Windows metafile);
    • develop separate diagrams for the system, subsystems and components of subsystems;
    • make the design of the diagrams uniform, using the same elements, abbreviations, icons, text styles, etc.

1.5. Resources to help you develop documentation

The Internet contains a huge amount of information that, to one degree or another, can help in the development of technical project documentation. Key resources are presented in the table below.

Table. SIS Technical Design Resources

Resource type	Information	Examples of resources
Internet portals of federal executive authorities	Regulations, guidelines, registers (including certified information security systems), databases (including databases of vulnerabilities and threats)	fstec.ru clsz.fsb.ru minsvyaz.ru/ru/
Internet portals of information security manufacturers, distributors of information security solutions	Description of information security solutions, operational documentation for information security, analytical materials and articles	securitycode.ru kaspersky.ru/ drweb.ru/ ptsecurity.ru/ infowatch.ru/ infotecs.ru/ cisco.com/c/ru_ru/index.html checkpoint.com altx-soft.ru
Specialized information security resources	Comparison of information security solutions, review articles on information security solutions, tests of information security solutions, in-depth technical information about information security technologies	anti-malware.ru bis-expert.ru safe.cnews.ru securitylab.ru/ vulners.com/ csrc.nist.gov itsecurity.com owasp.org sans.org


1.6. Examples of technical project stage documents

To understand the requirements for the content of documentation at the TP stage, below are examples of filling out the main documents (sections of documents).

1.6.1. Explanatory note to the technical project

The explanatory note is a fairly voluminous document, so here is an example of the content of the section “Main technical solutions” in part of one of the SIS subsystems - the security analysis subsystem.

ISS security analysis subsystem

Structure and composition of the subsystem

The security analysis subsystem (SAS) is designed to systematically monitor the security status of automated workstations (AWS) of personnel and organization servers. The basis of the ESD is the “Test” software tool produced by Information Security LLC. SZI Test has a certificate of FSTEC of Russia for compliance technical specifications(TU) on information security and on the 4th level of control over the absence of undeclared capabilities.

The ESD includes the following components:

• Test Server management server;
• Test Console management console.

A description of the subsystem components is presented in the table below.

Table. ESD components

Component	Description
Test Server Management Server	Provides management of scanning tasks, performs functions of monitoring the security status of the workstation and the organization's servers. Scanning parameters are set by the information security administrator on the Test Server management server. All collected information about scan results is stored in the Test Server server storage based on the Microsoft SQL Server 2008 database management system
Test Console	Allows the information security administrator to connect to the Test Server, view and change its configuration, create and modify scanning tasks, view information about the progress of tasks and the results of their execution. The management console is installed on the information security administrator's workstation

Providing functions

The ESD provides the following functions:

• implementation of proactive protection of the organization's workstations and servers by monitoring the status of information security;
• automation of processes for monitoring compliance with internal policies and certain security standards;
• reduction of costs for auditing and security control, preparation of status reports;
• automation of resource inventory processes, vulnerability management, monitoring compliance with security policies and change control.

Solution for a complex of hardware and software tools

The list of used ESD software and hardware is given in the table below.


Table. ESD software and hardware

ESD control server

Technical means

The physical server used as an ESD management server must meet the technical requirements for the software and OS installed on it, given in the table below.

Table. OS and software requirements for the ESD control server

Software	Technical requirements
	CPU	RAM, MB
Microsoft Windows Server 2008 R2	3000 MHz, 4 cores	8192
Microsoft SQL Server 2008 R2
Test Server software

Software

Management server OS

Windows 2008 R2 OS is installed on the management server in the normal manner from a boot distribution.

The management server OS is managed both locally from the console and via the RDP protocol.

Management server DBMS

The Microsoft SQL Server 2008 R2 database is installed under an account with local administrator rights using the standard installation wizard from the distribution kit supplied by the product developer.

Test Server software

Test Server software is installed on the management server using the standard installation wizard.

The initial setup and subsequent management of Test Server software in normal mode is carried out using the Test Console management console installed on the IS administrator's workstation.

IS administrator's workstation

Technical means

The existing workstation of an employee of the organizational unit responsible for providing information security, running the Microsoft Windows family of operating systems, is used as a platform.

The technical means of the information security administrator's workstation must have the following hardware configuration characteristics (at least recommended):

• CPU 2 GHz;
• RAM 4 GB;
• HDD 80 GB.

Software

Test Console software

The information security administrator's workstation on which the Test Console software is installed must operate under one of the following OS:

• Microsoft Windows 7, 32- and 64-bit;
• Microsoft Windows 8/8.1, 32- and 64-bit.

In addition, for the Test Console management console software to work correctly, Microsoft .NET Framework version 3.5 SP1 or higher must be installed on the information security administrator's workstation, and the security settings of the operating system used must allow access to the Test Server.

Installation of Test Console software on the ESD administrator's workstation is carried out using the standard Test Server software installation wizard with the selected option to install the Test Console management console and other default settings.

Interaction with adjacent systems

For ESD, adjacent are:

• firewall subsystem tools;
• Active Directory directory services;
• Workstation and servers of the organization.

To ensure network interaction with adjacent systems and directly between the ESD components themselves, the passage of the necessary network traffic must be organized.

To ensure the ability to receive updates to the knowledge base and Test software modules for the Test Server scanner, it is necessary to provide access to the update.com web server of the Information Security LLC company via port 443/tcp.

When scanning in PenTest mode, interaction between the Test Server scanner and the workstation and the organization's servers is carried out via the IP protocol. When scanning in Audit and Compliance modes, remote management protocols WMI, RPC, etc. are used. To scan hosts on devices with firewall functions, you must allow connections from the Test Server to the scanned hosts via IP. Accordingly, the Test Server must be provided with access to the network ports of the scanned nodes using the appropriate remote control protocols.

Since ESD, when scanning in Audit and Compliance modes, uses remote control protocols for analysis, Test software scanning tools must undergo authentication and authorization on the scanned node. In ESD, to scan nodes in the Audit and Compliance modes, accounts with administrative privileges are used in each type of node (workstation, server, application systems, DBMS, etc.).

All registered information security events are stored in the Microsoft SQL DBMS. These events can be sent to the information security event monitoring subsystem using special connectors.

Operation and maintenance of ESD

Subsystem users

Operation and maintenance of ESD tools is carried out by employees of the organization with the functional role of “IS administrator”.

An information security administrator is defined as a specialist whose tasks include:

• determining the scanning parameters of the organization’s nodes;
• setting up and launching scanning tasks;
• analysis of scan results for vulnerabilities, configuration errors or non-compliance with requirements in information systems technical standards;
• control over the elimination of vulnerabilities;
• formation of standards and requirements that apply to ensuring the security of the organization's workstations and servers.

System operating modes

Normal operating mode

In normal operation, the ESD operates 24 hours a day, 7 days a week.

In normal operation, the information security administrator performs:

• scheduled and unscheduled scanning of nodes;
• generating reports;
• updating knowledge bases and Test software modules.

Emergency operation

If the performance of the safety equipment is disrupted, the functioning of the subsystem is disrupted. Failure to operate ESD equipment does not affect the functioning of the organization's automated workstations and servers.

1.6.2. Functional structure diagram

Functional diagrams can be developed for the entire information security system or for part of it, for example, a subsystem or component.

An example of a general functional diagram of an ISS is shown in the figure below.

1.6.3. Structural diagram of a complex of technical means

The block diagram of a complex of technical means can be developed both for the entire ISS and for its parts - subsystems and components. The feasibility of developing diagrams for parts of the information security system is determined by the scale of the system and the required detail.

Example block diagram The complex of technical means of the NIB is presented in the figure below.