1、BRITISH STANDARDBS EN 62347:2007Guidance on system dependability specifications The European Standard EN 62347:2007 has the status of a British StandardICS 03.120.01g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g
2、48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 62347:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 September 2007 BSI 2007ISBN 978 0 580 54164 3National forewordThis British Standard is the UK implementation o
3、f EN 62347:2007. It is identical to IEC 62347:2006.The UK participation in its preparation was entrusted to Technical Committee DS/1, Dependability and terotechnology.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport t
4、o include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARD EN 62347 NORME EUROPENNE EUROPISCHE NORM
5、 March 2007 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2007 CENELEC - All rights of exploitation in any form and by any mea
6、ns reserved worldwide for CENELEC members. Ref. No. EN 62347:2007 E ICS 03.120.01 English version Guidance on system dependability specifications (IEC 62347:2006) Lignes directrices pour les spcifications de sret de fonctionnement des systmes (CEI 62347:2006) Anleitung zur Spezifikation der Zuverlss
7、igkeit von Systemen (IEC 62347:2006) This European Standard was approved by CENELEC on 2007-03-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
8、Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translati
9、on under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finlan
10、d, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Foreword The text of document 56/1138/FDIS, future edition 1 of IEC 62347, pr
11、epared by IEC TC 56, Dependability, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 62347 on 2007-03-01. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorse
12、ment (dop) 2007-12-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2010-03-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 62347:2006 was approved by CENELEC as a European Standard without any mo
13、dification. _ EN 62347:2007 2 CONTENTS INTRODUCTION.4 1 Scope.5 2 Normative references .5 3 Terms and definitions 5 4 Concepts dealing with system dependability.6 4.1 Understanding the system .6 4.2 System life cycle .8 4.3 System operation 10 4.4 System operating profile10 4.5 Dependability require
14、ments .11 5 Procedure for specifying system dependability .13 5.1 System specification process 13 5.2 System dependability specification process.13 5.3 Determining dependability values 14 5.4 Procedural steps for determining system dependability requirements 15 Annex A (informative) Evaluation of de
15、pendability characteristics 19 Annex B (informative) An example on developing a system dependability specification A home security system 26 Bibliography34 Figure 1 An example of system properties and related characteristics7 Figure 2 Overview of system life cycle stages 9 Figure 3 Relationships of
16、system operating profile and scenario in system operation.11 Figure 4 Overview of system specification process 14 Figure 5 Steps for determining system dependability requirements 16 Figure B.1 System configuration for normal mode of operation.30 Figure B.2 System configuration for panic mode of oper
17、ation.31 Figure B.3 System configuration for security service mode of operation .31 Table A.1 Examples of influencing factors under each influencing condition.24 Table A.2 Relationship of system properties with influencing conditions.25 Annex ZA (normative) Normative references to international publ
18、ications with theircorresponding European publications35EN 62347:2007 3 INTRODUCTION A system is a physical and/or virtual entity. It is necessary sometimes to define a systems boundary so that it can be distinguished or separated from other systems. A system interacts with its surroundings or envir
19、onment to fulfil a specific need or purpose, or to achieve a defined objective. This is accomplished through the interaction of the systems elements representing the necessary functions designed to meet the intended objective. Determining the functions needed to meet a specific objective represents
20、the process of developing a system specification. Detailed system design begins only after the functions have been identified. Systems may vary in their complexity structurally and functionally. A system can consist of hardware, software, and human elements, or a combination of any of these elements
21、 to perform the necessary functions. A system consisting of a single function can be a product, such as a television set or a software program for lighting controls. A system performing multiple functions can be a home theatre system or an aircraft. Individual systems with defined boundaries can be
22、joined together to form a complex set of interacting systems such as a power distribution network or an internet protocol service. System specification establishes the envelope and boundary for the system. System structure is often hierarchical linking subsystems and interacting systems. System spec
23、ification is applicable to all systems under the generic definition of system irrespective of its hierarchy. It does not replace or substitute for use a product specification, which provides specific details of the product requirements. The dependability of a system infers that the system is perceiv
24、ed to be trustworthy and has the ability to provide service upon demand as desirable performance attributes. Such performance attributes can be achieved through the incorporation of dependability into the functions. Dependability implies the awareness of user confidence acquired through prior experi
25、ence of the system with reliable performance results in meeting user expectations. This International Standard provides the rationale on the importance of dependability in system specification by functions. It presents a procedure for determining system dependability requirements. For generic system
26、 operation, the process of determining the functions needed to meet system dependability objective is described. For specific system operation, the concept of an operating profile is introduced to establish the requirements of functions in an environment relevant to the specific system operation. Th
27、is International Standard is based on the system model and categorization of functions established in the IEC 61069 series. Relevant technical processes for the definition and analysis of system requirements are adopted from ISO/IEC 15288. The procedural steps and processes for determining system de
28、pendability requirements are presented with applicable examples. IEC 60300-1 and IEC 60300-2 are used to guide dependability management. This International Standard extends the dependability specification process to address functions as a prerequisite for system design. It complements IEC 60300-3-4
29、in specification of dependability requirements for products and equipment. The technical process for engineering dependability into systems is described in IEC 60300-3-15. EN 62347:2007 4 GUIDANCE ON SYSTEM DEPENDABILITY SPECIFICATIONS 1 Scope This International Standard gives guidance on the prepar
30、ation of system dependability specifications. It provides a process for system evaluation and presents a procedure for determining system dependability requirements. This International Standard is not intended for certification or to perform conformity assessment for contractual purposes. It is not
31、intended to change any rights or obligations provided by applicable statutory or regulatory requirements. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, th
32、e latest edition of the referenced document (including any amendments) applies. IEC 60050(191), International Electrotechnical Vocabulary (IEV) Chapter 191: Dependability and quality of service ISO/IEC 15288, Systems engineering System life cycle processes 3 Terms and definitions For the purposes of
33、 this document, the terms and definitions given in IEC 60050(191) and the following apply. 3.1 system set of interrelated or interacting elements ISO 9000:2005, 3.2.1 NOTE 1 In the context of dependability, a system will have: a defined purpose expressed in terms of intended functions; stated condit
34、ions of operation/use; and defined boundaries. NOTE 2 The structure of a system may be hierarchical. IEC 60300-1, 3.6 NOTE 3 For some systems, such as Information Technology products, data is an important part of the system elements. 3.2 operating profile complete set of tasks to achieve a specific
35、system objective NOTE An operating profile is the sequence of tasks to be performed by the system to achieve its operational objective. The operating profile represents a specific operating scenario for the system in operation. EN 62347:2007 5 3.3 function elementary operation performed by the syste
36、m which, combined with other elementary operations (system functions), enables the system to perform a task IEC 61069-1, definition 2.2.5 NOTE For some systems, information and data are important parts of the system elements. 3.4 element combination of components that form the basic building block t
37、o perform a distinct function NOTE An element may comprise hardware, software, information and/or human components. 3.5 influencing condition condition set forth by external influencing elements and/or other factors that interact with and affect system performance NOTE Influencing conditions may als
38、o include regulations and constraints. 4 Concepts dealing with system dependability 4.1 Understanding the system 4.1.1 Purpose and objective A system is designed for a purpose. A system must have a defined objective to achieve its purpose. The purpose of a home theatre system is to provide cinema-li
39、ke entertainment in a home environment. The objectives may include users perception of a clear picture vision and superb sound quality, reliability and safety in operation, and ease of installation and upgrade. A system may have a specific objective to perform a dedicated task, such as an aircraft c
40、arrying cargo to reach a delivery target. The objectives of a system may include the com-pletion of a sequence of tasks, such as delivering different payloads to different destinations. Defining the system to meet its generic or specific objectives is an important prerequisite of specifying the syst
41、em requirements. A system with multiple functions and complex operating scenario often involves external interacting systems to achieve its objectives. A system may also evolve with time, resulting from enhancements of its performance capability, to sustain service demands in operation and for marke
42、t competition. 4.1.2 System properties and characteristics A system has a set of properties specifically assigned, selected or designed into the system to meet its intended objectives. Specific system properties are used to develop the needed functions to perform the tasks. These properties represen
43、t the special features or attributes inherent in the system. They may be categorized in major groupings as defined in IEC 61069 series. Under each group is a set of characteristics relevant to and dominant in that group. The functions are derived from those system properties by means of interacting
44、elements within the system. The interacting elements are designed to provide specific characteristics capable of delivering the system functions and to carry out the tasks once these functions can be realized. System characteristics may be qualitative or quantitative. Figure 1 shows an example of th
45、e system characteristics grouped under various system properties. EN 62347:2007 6 System propertiesFunctionality capability capacity coverage configurability programmability expandability Performance adequacy precision response time repeatability Operability access interface user-friendliness simpli
46、city robustnessDependabilityavailabilityreliabilitymaintainabilitymaintenance supportSupportability serviceability upgradeability disposability Application specifics safety security immunity IEC 2131/06 NOTES Functionality: the extent to which the processing, monitoring and control functions are pro
47、vided. Performance: the extent to which the provided functions can be executed under defined operational and environmental conditions. Operability: the extent to which information can be effectively communicated via the human interfaces and established protocols. Dependability: the extent to which t
48、he system can be relied upon to perform its intended functions under defined operational and environmental conditions at a given instant of time or over a given time interval. Supportability: the extent to which the system can be supported and maintained for continual operation. Application specific
49、s: the extent to which the system can be designed for risk avoidance and risk containment, such as security operational measures. Figure 1 Example of system properties and related characteristics 4.1.3 Influencing conditions In order to determine which functions have the selected characteristics appropriate to achieving a specific objective, it is necessary to define the conditions that the system is capable of withstanding or meeting the demands and duration of the a
