1、 INCITS/ISO/IEC TR 9789:1994 2015 (ISO/IEC TR 9789:1994, IDT) Information technology - Guidelines for the organization and representation of data elements for data interchange - Coding methods and principles (TECHNICAL REPORT) INCITS/ISO/IEC TR 9789:1994 2015 PDF disclaimer This PDF file may contain
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5、for Information Technology Standards) as an American National Standard. Date of Registration: 11/1/2015 Published by American National Standards Institute, 25 West 43rd Street, New York, New York 10036 Copyright 2015 by Information Technology Industry Council (ITI). All rights reserved. These materi
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8、EPORT ISO/IEC TR 9789 First edition 1994-l 2-l 5 Information technology - Guidelines for the organization and representation of data elements for data interchange - Coding methods and principles Technologies de /information - Principes directeurs pour Iorganisation et la reprbentation des Bkments de
9、 don type 2, when the subject is still under technical development or where for any other reason there is the future but not immediate possibility for an agreement on an International Standard; - tme 3, when a technical committee has collected data of a different kind from that which is normally pub
10、lished as an International Standard; (“state of the art“, for example). Technical reports of types 1 and 2 are subject to review within three years of publication, to decide whether they can be transferred into International Standard. Technical reports of type 3 do not necessarily have to be reviewe
11、d until the data they provide are considered to be no longer valid or useful. ISO/IEC TR 9789, which is a Technical Report of type 3, was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology Subcommittee 14, Data element principles. Q ISO/IEC ISO/IEC TR 9789:1994(E) Introducti
12、on This Technical Report is a guide to develop and implement coded representations. Coding covers the way and the form in which data are expressed. The increased use of data processing and electronic data interchange heavily relies on accurate, reliable, controllable and verifiable data recorded in
13、data bases. In formal communication and storage data are expressed in symbols (usually digits or letters), arithmetic numbers and descriptions, which should have a fixed stable meaning for every one involved and thereby be suitable for purposes of processing and communication. This Technical Report
14、presents the objectives of coding, the characteristics, advantages and disadvantages of different coding methods, a survey of the features of codes and guidelines for the design of codes. V TECHNICAL REPORT 0 ISO/IEC ISO/IEC TR 9789:1994(E) Information technology - Guidelines for the organization an
15、d representation of data elements for data interchange - Coding methods and principles 1 Scope This Technical Report provides general guidance on the manner on which data can be expressed by codes. It describes the objectives of coding, the characteristics, advantages and disadvantages of different
16、coding methods, the features of codes and gives guidelines for the design of codes. This Technical Report is not directed toward any specific application area nor dependent on any design method for application systems or data interchange. 2 References 2.1 General references ISO/IEC 646:1991, Informa
17、tion technology - IS0 7-bit coded character set for information interchange. IS0 2382-4:1987, Information processing systems - Vocabulary - Part 04:Organization of data. IS0 2375:1985, Data processing - Procedure for registration of escape sequences. IS0 7064:1983, Data processing - Check character
18、systems. ISO/IEC 11179-3:1994, Information technology - Specification and standardization of data elements - Part 3: Basic attributes of data elements. 2.2 Examples of applications of this Technical Report IS0 9735:1988, Electronic data interchange for administration, commerce and transport (EDIFACT
19、) - Application level syntax. IS0 8601:1988, Data elements and interchange formats - Information interchange - Representation of dates and times. IS0 3166:1993, Codes for the representation of names of countries. ISO/IEC TR 9789:1994(E) o ISOAEC 3 Definitions For the purpose of this Technical Report
20、, the following definitions apply. 3.1 attribute: A characteristic of an object. 3.2 character set: A finite set of different characters that is complete for a given purpose. Example: The international reference version of the character set of IS0 646. 3.3 code: A collection of rules that maps the e
21、lements of one set on to the elements of another set. NOTES 1. The elements may be characters or character strings. 2. The first set is the coded set and the other set is the code element set. 3. An element of the code element set may be related to more than one element of the coded set but the reve
22、rse is not true. 3.4 code element: The result of applying a code to an element in a coded set. Examples: 1 “ CDG “ as the representation of Paris Charles de Gaulle in the code for three-letter representation of airport names. 2 The seven binary digits representing the delete character in IS0 646. 3.
23、5 code element set: The result of applying a code to all elements of a coded set. Example: All the three-letter international representations of airport names. 3.6 code set: Synonym of code element set. 3.7 code value: Synonym of code element. 3.8 coded representation: Synonym of code element. 3.9 C
24、oded set: A set of elements which is mapped on to another set according to a code. Example: A list of the names of airports which is mapped on to a corresponding set of three-letter abbreviations. 3.10 coding scheme: Synonym of code. 3.11 data code: See preferred term code element. 2 o ISOAEC ISO/IE
25、C TR 9789:1994(E) 3.12 data element instance: An occurrence of a data element type. 3.13 data element type: A category of data which represents a concept and whose properties are expressed as a set of data element type attributes which permit it to support information interchange. 3.14 delimiter: On
26、e or more characters used to indicate the beginning or the end of a character string. 3.15 entity: Any concrete or abstract thing of interest, including associations among things. 3.16 field: A specified area on a data medium or in storage, used for a particular class of data elements. 3.17 identifi
27、er: One or more characters used to identify or name a data element type and possibly to indicate certain properties of that data element type. 3.18 key: An identifier within a set of data element types. 3.19 position: Any location in a string that may be occupied by an element and that is identified
28、 by a serial number. 3.20 string: A sequence of elements of the same nature, such as characters, considered as a whole. 3.21 table: An arrangement of data each item of which may be identified by means of arguments or keys. 4 Principles of coding 4.1 Information and coding In daily life information i
29、s understood as facts of and propositions about all the concrete or abstract things of interest expressed by: data, messages and further particulars. Information is necessary for the proper execution of any conceivable task be it in administration, commerce, transport, science, etc. Accurate, object
30、ive and unambiguous information is a prerequisite in cases of computer based information systems and the data interchange between them. In formal information systems data is expressed in symbols (usually digits or letters), arithmetic numbers and descriptions, which should have a fixed, stable meani
31、ng for every one involved and thereby be suitable for purposes of processing and communication. Users, irrespective of their function or tasks, should be able to understand, interpret and handle their information correctly. Information shared by different user groups or application systems has to ha
32、ve an agreed definition e.g. semantic meaning of a concept (connotation) and all instances of a concept (denotation) and an agreed representation. 3 ISO/IEC TR 9789:1994(E) o ISO/IEC Coding covers the way and the form in which data is expressed by codes. It is necessary to make clear agreements on t
33、hese representations. An explanation of the representation forms and code elements is part of the specification of data. 4.2 Coding By coding is understood the rule-based assignment of code elements to a named and defined set of elements in an orderly way. Coding is mostly done by means of symbols,
34、(usually digits or letters), resulting in a concise representation. Example: The assignment of code element: “CDG“ as the concise representation of airport name: “Paris Charles de Gaulle“. This airport name belongs to the set of airport names maintained by the International Air Transport Association
35、 (IATA). IATA has set the rules for establishing the concise representations. Coding is a necessary tool for information processing. Coding of information enables it to be recorded, interpreted, processed and transmitted by humans and/or by machines. All kinds of information can be coded: informatio
36、n about products, persons, processes, documents, countries, currencies, packages, etc. Before making agreements on the coding methodology, i.e. the representation of information concerning events, actions, concrete or abstract objects in the real world, it must be investigated which data are relevan
37、t for the intended application. Information analysis of the universe of discourse concerned has to determine the role of the data in the information structure thereof. In doing this a clear distinction should be made between identification, classification and reference needs. 5 Coding objectives Inf
38、ormation about any abstract or concrete object, action, or event of interest, (its characteristics or attributes) can be coded. Before making agreements on the configuration of their representation, the coding rules, it is necessary to determine the objective of the coding effort. It is not enough t
39、o design an ordered short representation of certain data. First the information requirements must be clear. The following requirements generally occur: - identification - classification - key to further information. When data modelling is applied for the specification of application systems or messa
40、ges for use in data interchange, the objectives of the users in the application environment will determine the choice of the entities and attributes to be taken into account as well as their interrelationship. The methods to be used for identification, classification or referencing will depend on th
41、ose objectives. 4 Q ISO/IEC ISO/IEC TR 9789:1994(E) 5.1 Identification The purpose of identification is to distinguish elements of a set from each other. To be able to do this it must first be determined which characteristics have to be taken into account. Based on the selected characteristics compa
42、risons can be performed and it can be ascertained whether an element of the set is equal to another element or different from it. To which degree of detail characteristics have to be recorded to indicate similarity or difference of elements of the set, depends on the area of application for which id
43、entification is needed. Examole For its stock control of stationery an organization wants to identify various types of sheets of paper. Sometimes it may be sufficient to distinguish the various formats: A3, A4 or AS. Depending on the utilization of the sheets of paper other characteristics may be ad
44、ded, such as thickness, weight, chemical composition. If no specific requirements have to be met the recording of the format may suffice. In other cases, where handling and processing of the sheets of paper are critical the necessary characteristics have to be mentioned. so, identification can be de
45、fined as: The systematic registration of characteristics of elements of a set in such a way that they can be distinguished from each other. The characteristics to be distinguished are inalienably part of an object or concept of interest. The extent of the details to be observed is dependent on the u
46、sers objectives and the area of application. These criteria result in the design or selection of an identification system. Examoles of details to be distinauished: In the real world a person has a family name and a given name, is born in a country, on a certain date, resides in a country, his eyes h
47、ave a certain colour, etc. Application 1: In a governmental application system one wants to distinguish the colours of eyes of citizens. Application 2: In an application system for medical research project one wants to distinguish the colours of eyes of human beings. In these applications the requir
48、ed degree of discrimination need not be identical. In the medical research application, it may be required that more colours of eyes of human beings are to be distinguished than in an application of a governmental body registering the colours of eyes of citizens. In practice this may result into a c
49、ompromise when selecting an identification system. Often the choice of a system is then determined on basis of the wish to have a minimum number of identification 5 ISO/IEC TR 9789:19946E) o ISO/IEC systems to accommodate a maximum number of functions. The objectives and applications determine which intrinsic characteristics will be taken into consideration. 5.2 Classification The purpose of classification is to group objects or concepts of interest into classes in accordance with predetermined c
