Environmental Data Coding Specification (EDCS)

4 Concepts

4.1 Introduction and table of contents

4.1.1 Table of contents

4.1.2 Overview

This International Standard supports the encoding and communication of qualitative and quantitative information associated with environments, both real and virtual. This is accomplished by specifying nine EDCS dictionaries of environmental concepts and the EDCS application program interface (API).

In addition, this International Standard specifies profiles for defining subsets of the standard, a registration process for extending the content of the standard, and requirements for conformance to the standard.

4.1.3 Abbreviated terms

In this International Standard, abbreviated terms are used for EDCS dictionaries, codes, and labels, as well as other terms. In HTML browsers that support presentation of the HTML title attribute, the full name of the abbreviated term for the name of an EDCS dictionary, a code associated with an EDCS dictionary, and/or a label associated with an EDCS dictionary appears when the cursor is positioned over the abbreviation. The abbreviated terms used in this International Standard are listed in Table 3.3.

4.1.4 Capitalization

In this International Standard, the use of first letter capitalization is restricted to:

1. the name of this International Standard,
2. the names of EDCS dictionaries,
3. proper nouns, and
4. the first word of titles.

In addition, all letters in an abbreviation are capitalized.

The rules governing capitalization in concept labels are given in 10.3.

4.2 EDCS dictionaries

An EDCS dictionary is a list of EDCS dictionary entries each of which specifies a single concept. Each EDCS dictionary contains entries of a similar nature, however each entry shall be unique. Each EDCS dictionary entry shall consist of the following fields:

1. concept definition;
2. label;
3. code;
4. reference type, reference, and supplemental references; and
5. other EDCS dictionary-dependent information such as figures, value types, unit symbols, and unit equivalence classes.

The nine EDCS dictionaries are:

1. EDCS Classification (EC) Dictionary,
2. EDCS Attribute (EA) Dictionary,
3. EDCS Attribute Value Characteristic (EV) Dictionary,
4. EDCS Attribute Enumerant (EE) Dictionary,
5. EDCS Unit (EU) Dictionary,
6. EDCS Unit Scale (ES) Dictionary,
7. EDCS Unit Equivalence Class (EQ) Dictionary,
8. EDCS Organizational Schema (EO) Dictionary, and
9. EDCS Group (EG) Dictionary.

The set of EDCS dictionaries are interrelated in the following ways:

1. For each entry in the EA Dictionary of EDCS attribute value type ENUMERATION (see Table 4.4), there is a set of entries in the EE Dictionary that specifies the allowed values of that EA Dictionary entry.
2. For each entry in the EO Dictionary, there is a set of entries in the EG Dictionary that specifies the EG members of that EO Dictionary entry.

Additional entries may be added to most EDCS dictionaries through the process of registration (see 4.15).

4.3 Fields for EDCS dictionary entries

4.3.1 Concept definition

The concept definition field of an EDCS dictionary entry shall contain the definition of the concept embodied by that entry. The concept definition shall be a precise statement of the nature, properties, scope, and/or essential qualities of the concept embodied in the entry.

4.3.2 Label

The label field of an EDCS dictionary entry shall contain a human-understandable designator that is used to denote the concept embodied by that entry. Labels in this International Standard may include either the name or names for that concept.

Each label in this International Standard shall:

1. uniquely denote a concept within an EDCS dictionary,
2. be a succinct expression of the concept it denotes,
3. be represented as a character string, and
4. be human-understandable.

For presentation purposes only, a long label may be displayed on more than one line by using a hyphen (-) to separate the label before an underscore (_) character. For example, the label ACOUSTIC_AMBIENT_NOISE_SPECTRAL_MODEL may be displayed for presentation purposes as:

ACOUSTIC_AMBIENT_NOISE-
_SPECTRAL_MODEL.

Additional guidelines for the creation of labels are specified in 10.3.

4.3.3 Code

The code field of an EDCS dictionary entry shall contain a compact and not necessarily human-understandable designator that is used to denote the concept embodied by that entry.

Each code in this International Standard shall:

1. uniquely denote a concept within an EDCS dictionary,
2. be represented as an integer, and
3. be assigned sequentially in increasing order within an EDCS dictionary, beginning at 1.

There is a one-to-one relationship between labels and codes in the same EDCS dictionary. Therefore, a label and a code may be used interchangeably to denote the same concept.

Application program interfaces and exchange formats often represent codes. Such representations shall be capable of distinguishing 2³¹-1 different codes. Negative codes are not permitted in this International Standard, but they may be used in a non-conforming implementation for experimentation.

4.3.4 Fields used for referencing

4.3.4.1 Introduction

The reference type, reference, and supplemental references fields of an EDCS dictionary entry serve the following purposes:

1. specification of the nature of the relationship between the concept embodied by that entry and the concept optionally cited in the reference field,
2. identification of the source of the concept embodied in that entry, and
3. provision of additional information useful in understanding that entry.

The reference type and reference fields are closely related while the supplemental references field provides additional information.

4.3.4.2 Reference type

The reference type field of an EDCS dictionary entry specifies the nature of the relationship between the concept embodied by that entry and the concept optionally cited in the reference field (see 4.3.4.3). If the reference field (see 4.3.4.3) contains an optional citation, the reference type field shall contain the two character abbreviation for the EDCS reference type that specifies the nature of that reference. The EDCS reference types are specified in Table 4.3.

The reference and associated reference type for each EDCS dictionary entry shall be in the following order of preference: AR, PR, and then IR. No reference shall be given (and therefore no EDCS reference type is given either) only if no reference of EDCS reference type AR, PR, or IR can be used.

Additional requirements that apply to the contents of the reference type field are specified in 10.5.3.

4.3.4.3 Reference

The reference field of an EDCS dictionary entry may contain one citation (see 10.5.2) that identifies the source of the concept. The citation in the reference field shall be in the format specified in 10.5.2. Additional requirements for the contents of the reference field are specified in 10.5.4. If the wording of the concept definition was derived from a different source than the concept itself and the concept is not a commonly understood concept, a citation to the source of the wording shall be included within the concept definition field.

4.3.4.4 Supplemental references

The supplemental references field of an EDCS dictionary entry may contain one or more citations that provide information useful in understanding that entry. Each citation in the supplemental reference field shall be in the format specified in 10.5.2. Additional requirements for the contents of the supplemental references field are specified in 10.5.5. Because supplemental references are always for information only, these references do not have an EDCS reference type.

A citation in the reference field of an EDCS dictionary entry shall not be repeated for the same entry as a citation in the supplemental reference field even if it provides information useful in understanding that EDCS dictionary entry.

4.3.5 Other fields

In addition to common fields, some EDCS dictionaries have specialized fields. Such specialized fields are described for each dictionary in the following sections. However one field, "Figure(s)", is common to the EC, EA, and EE dictionaries. A figure is an illustrative example of the concept. Inclusion of a figure is optional. Figures may be line drawings, images, or other graphics. Additional requirements for figures are given in 10.5.6.

4.4 EDCS classifications

This International Standard specifies an EDCS Classification Dictionary. Each entry in this dictionary is termed an EDCS classification (EC). An EDCS Classification Dictionary entry specifies the type of an environmental object.

Within the scope of the EDCS Classification Dictionary, each EC shall have:

1. a unique concept definition,
2. a unique EDCS classification label (ECL), and
3. a unique EDCS classification code (ECC).

In addition, each EC may have:

1. a reference type,
2. a reference,
3. supplemental references, and
4. figures.

The EDCS Classification Dictionary is presented in 27 tables (see Table 5.4). One table contains all deprecated ECs (see Table A.3). Each of the other 26 tables, one table for each letter of the alphabet, consists of ECs with the same first character of their ECLs. Within each table, the ECs are ordered alphabetically by the ECL.

4.5 EDCS attributes

4.5.1 Dictionary entries

This International Standard specifies an EDCS Attribute Dictionary. Each entry in this dictionary is termed an EDCS attribute (EA). An EA identifies one aspect of the state of an environmental object and specifies how a value for that aspect can be provided. The state of an environmental object therefore consists of the set of values for each of the aspects identified by its EAs.

Each EA has a type that determines the nature of the information represented by its values. In this International Standard, the type of an EA is called its EDCS attribute value type (see Table 4.4).

Within the scope of the EDCS Attribute Dictionary, each EA shall have:

1. a unique concept definition,
2. a unique EDCS attribute label (EAL),
3. a unique EDCS attribute code (EAC), and
4. an EDCS attribute value type.

In addition, each EA may have:

1. a reference type,
2. a reference,
3. supplemental references, and
4. figures.

The values of EAs whose EDCS attribute value type is REAL (see Table 4.4) represent physical quantities (see 3.2.21). If the EDCS attribute value type is REAL, the EA shall have an associated EDCS unit equivalence class (see 4.10) to characterize the physical quantity.

The EDCS attribute value types are specified Table 4.4.

The EDCS Attribute Dictionary is presented in 27 tables (see Table 6.4). One table contains all deprecated EAs (see Table A.4). Each of the other 26 tables, one table for each letter of the alphabet, consists of EAs with the same first character of their EALs. Within each table, the EAs are ordered alphabetically by the EAL.

4.5.2 Attribute instances

When a value is assigned to an instance of an EA, additional information may be required depending on the EDCS attribute value type of the EA.

An instance of an EA whose EDCS attribute value type is REAL shall have:

1. an EDCS unit (see 4.8) that belongs to the EDCS unit equivalence class of that EA, and
2. an EDCS unit scale (see 4.9) that specifies a power of ten or 2¹⁰ that is a multiplicative scale factor for the value of the instance of that EA.

An instance of an EA whose EDCS attribute value type is STRING shall specify the language and/or the country in whose context that language is to be interpreted for the characters composing the STRING (see 9.2.5.4).

An instance of an EA whose EDCS attribute value type is REAL, INTEGER, or COUNT shall have an associated EDCS numeric value type (see Table 4.5). The EDCS numeric value type specifies whether the values of that instance are a single number or an interval of numbers. The EDCS numeric value types are specified in Table 4.5.

4.6 EDCS attribute value characteristics

This International Standard specifies an EDCS Attribute Value Characteristic Dictionary. Each entry in this dictionary is termed an EDCS attribute value characteristic (EV).

For the purpose of EV specifications, an EA instance collection shall mean any user-defined set, collection, list, array, hierarchy, container, or any other data structure of instances of a single EA entry. If such a data structure contains instances of several EAs, the EA of interest shall be identifiable.

An EV specifies information concerning:

• a characteristic of an individual EA instance,
• a characteristic common to each instance in an EA instance collection, or
• a characteristic of the entirety of an EA instance collection, rather than its individual member instances.

EV entries may be used for various purposes. These purposes include providing:

• indication that a usable value is not provided by an EA instance and to convey information about why the instance value is not usable,
• information about an EA instance whose value is a number that cannot be directly represented,
• qualitative information about the state of the value provided by an EA instance,
• ancillary information about the EA instance, or
• information concerning the entirety of an EA instance collection.

Within the scope of the EDCS Attribute Value Characteristic Dictionary, each EV shall have:

1. a unique concept definition,
2. a unique EDCS attribute value characteristic label (EVL),
3. a unique EDCS attribute value characteristic code (EVC),
4. a specification of whether an EV instance is required to be assigned an EV value, and
5. a specification of the EDCS attribute value types to which it applies.

In addition, each EV may have:

1. a reference type,
2. a reference, and
3. supplemental references.

The EDCS Attribute Value Characteristic Dictionary is presented in Tables 6.32 and 6.33.

The information specified by EVs is either completely provided by the EV entry concept definition or by the combination of the concept definition and a value for the EV instance, termed the EV value. The requirement that an EV instance provide an EV value is determined by the EV entry concept definition. An EV that requires an EV value provides, according to the concept definition, either ancillary information about the EA instance or information concerning the entirety of an EA instance collection.

For EVs that require an EV value, if the EV value is of type REAL, the EV instance is required to specify a SCALE and a UNIT and the EQ of the UNIT shall match the corresponding EA.

4.7 EDCS attribute enumerants

This International Standard specifies an EDCS Attribute Enumerant Dictionary. Each entry in this dictionary is termed an EDCS attribute enumerant (EE). An EDCS Attribute Enumerant Dictionary entry specifies a member of the set of values of an EA whose EDCS attribute value type is ENUMERATION.

Within the scope of that EA, each member of its set of EEs shall have:

1. a unique concept definition,
2. a unique EDCS attribute enumerant label (EEL), and
3. a unique EDCS attribute enumerant code (EEC).

In addition, each EE may have:

1. a reference type,
2. a reference,
3. supplemental references, and
4. figures.

Since an EE is unique only within the scope of an EA, its concept can only be interpreted in connection with the concept of the scoping EA.

The EDCS Attribute Enumerant Dictionary is presented in 27 tables (see Table 6.35). One table contains all deprecated EEs (see Table A.5). Each of the other 26 tables, one table for each letter of the alphabet, consists of EAs with the same first character of their EALs, however, only EAs whose EDCS attribute value type is ENUMERATION are included. The EAs are ordered alphabetically by their EALs in each table, with each EA followed by its associated EEs. The EEs for each EA are presented in a natural order.

4.8 EDCS units

This International Standard specifies an EDCS Unit Dictionary. Each entry in this dictionary is termed an EDCS unit (EU). An EDCS Unit Dictionary entry characterizes the values of physical quantities in conformance to the International System of Units (SI) as specified in ISO 80000. Where possible, units of measure used in this International Standard are either taken from or derived from those specified in ISO 80000.

Within the scope of the EDCS Unit Dictionary, each EU shall have:

1. a unique concept definition,
2. a unique EDCS unit label (EUL),
3. a unique EDCS unit code (EUC),
4. a physical quantity, and
5. an EDCS unit equivalence class (see 4.10).

In addition, each EU may have:

1. a symbol,
2. a reference type,
3. a reference, and
4. supplemental references.

The EDCS Unit Dictionary is presented in five tables: two tables of EUs derived from SI (see Table 7.5 and Table 7.6), one table of EUs outside the scope of SI (see Table 7.7), and two tables of non-SI EUs in common usage (see Table 7.8 and Table 7.9). Any deprecated EUs will be placed in a table in A.6. Within each table, the EUs are ordered alphabetically by the EUL.

4.9 EDCS unit scales

This International Standard specifies an EDCS Unit Scale Dictionary. Each entry in this dictionary is termed an EDCS unit scale (ES). An EDCS Unit Scale Dictionary entry specifies a power of ten or 2¹⁰ that is a multiplicative scale factor that is used in expressing the value of an instance of an EA.

Within the scope of the EDCS Unit Scale Dictionary, each ES shall have:

1. a unique concept definition,
2. a unique EDCS unit scale label (ESL),
3. a unique EDCS unit scale code (ESC), and
4. a symbol.

In addition, each ES may have:

1. a reference type,
2. a reference, and
3. supplemental references.

The EDCS Unit Scale Dictionary is presented in two tables with the ESs ordered by the value of the multiplicative constant (scale factor) (see Table 7.9 and Table 7.10).

4.10 EDCS unit equivalence classes

This International Standard specifies an EDCS Unit Equivalence Class Dictionary. Each entry in this dictionary is termed an EDCS unit equivalence class (EQ). An EDCS Unit Equivalence Class Dictionary entry is a set of EUs that characterize the same physical quantity.

Within the scope of the EDCS Unit Equivalence Class Dictionary, each EQ shall have:

1. a unique concept definition,
2. a unique EDCS unit equivalence class label (EQL),
3. a unique EDCS unit equivalence class code (EQC), and
4. a set of EU members.

The EDCS Unit Equivalence Class Dictionary is presented in three tables ordered alphabetically by the EQL (see Table 7.12). Within each table, the EQs are ordered alphabetically by the EQL.

4.11 EDCS organizational schema

This International Standard specifies an EDCS Organizational Schema Dictionary. Each entry in this dictionary is termed an EDCS organizational schema (EO). An EDCS Organizational Schema Dictionary entry specifies an organizational schema consisting of a set of EGs (see 4.12).

Within the scope of the EDCS Organizational Schema Dictionary, each EO shall have:

1. a unique concept definition,
2. a unique EDCS organizational schema label (EOL), and
3. a unique EDCS organizational schema code (EOC).

In addition, each EO may have:

1. a reference type,
2. a reference, and
3. supplemental references.

The EDCS Organizational Schema Dictionary is presented in one table ordered alphabetically by the EOL (see Table 8.4).

4.12 EDCS groups

This International Standard specifies an EDCS Group Dictionary. Each entry in this dictionary is termed an EDCS group (EG). An EDCS Group Dictionary entry collects ECs and EAs based on a common context. The ECs and EAs in an EG shall be called members of the EG. Each EC and each EA may be a member of more than one EG.

Each EG shall be a member of exactly one EO. No organization shall be required among the EGs in an EO. The EGs either may or may not form a hierarchy. When an EO has the property that each EC and each EA is a member of at least one EG in the EO, the EO is called complete. All EOs in this International Standard shall be complete.

Within the scope of each EO, each member of its set of EGs shall have:

1. a unique concept definition,
2. a unique EDCS group label (EGL), and
3. a unique EDCS group code (EGC).

In addition, each member of its set of EGs may have:

1. a reference type,
2. a reference, and
3. supplemental references.

The EDCS Group Dictionary is presented in one table with the EOs ordered alphabetically by EOL and with each EO followed by its member EGs (see Table 8.6). The EGs for each EO are ordered alphabetically by the EGL.

4.13 EDCS profiles

To meet the requirements of many different applications, the scope of this International Standard is broad. A mechanism is needed to specify subsets and choose options that are tailored to particular purposes. This International Standard specifies EDCS profiles for this purpose.

Each profile shall specify a subset of this International Standard and its registered concepts (see 10.16).

Within the scope of this International Standard, each EDCS profile shall have:

1. a unique profile description;
2. a unique profile label;
3. a unique profile code;
4. the edition number of the EDCS standard and any associated amendment(s) from which the entries in the profile are obtained, and whether any registered entries from the International Register of Items are included in the profile;
5. a list of EDCS dictionaries used in the profile;
6. for each listed EDCS dictionary, a list of entry labels from that dictionary; and
7. optionally, EDCS profile constraints that restrict the use of either EDCS dictionary entries, or the relationships among EDCS dictionary entries, or both.

The list of entry labels from each EDCS dictionary may be explicit or may be expressed in a clear and unambiguous short-hand form that, when expanded, ensures the intended list is produced.

EXAMPLE 1    "All ECs".

EXAMPLE 2    "All EAs starting with letter G".

EXAMPLE 3    "All ECs in the HYDROLOGY group".

EXAMPLE 4    "All ECs in the profile EDCS_2_0_HIGHWAY_PROJECT_PROFILE", where EDCS_2_0_HIGHWAY_PROJECT_PROFILE is the label of a previously registered profile.

The guidelines for EDCS profile constraints are specified in 10.16.

Two profiles are specified in this International Standard. Additional profiles may be specified by registration (see 4.15). The standardized profiles are presented in Clause 11. The EDCS default profile is presented in 11.4.1. The EDCS unit profile is presented in 11.4.2. Standardized EDCS profiles that are deprecated are presented in A.15.

4.14 EDCS application program interface

This International Standard specifies an EDCS application program interface. This EDCS application program interface includes several functions (see 9.6). These functions include the following capabilities:

1. a function to convert between values of instances of EAs whose EDCS attribute value type is REAL that are given with respect to different EUs and/or ESs, and
2. a function to determine the highest standardized EDCS code and the highest registered EDCS code in each EDCS dictionary.

The values of some EAs measure physical quantities and have an associated EU and ES. Any of several EUs in the same EQ might be used to measure the same physical quantity, with each EU most appropriate for some application. Similarly, any of several ESs might be used to scale the values of the same physical quantity, with each ES most appropriate for some application. Therefore, applications may need to convert a value specified with respect to an EU and ES to a value specified with respect to a different EU and ES. The EDCS application program interface specifies data types and a function for conversion between values given with respect to different EUs and ESs.

Concepts in each EDCS dictionary may be specified either in this International Standard or by registration (see 4.15). An implementation either may or or may not support all standardized and/or registered concepts. Therefore, there is a need to be able to determine the highest standardized EDCS code and the highest registered EDCS code in each EDCS dictionary that an implementation supports. The EDCS application program interface specifies data types and a function for determining these values.

This International Standard specifies a set of abstract data types that associate EDCS labels with EDCS codes. The application program interface is specified in Clause 9.

4.15 Registration

This International Standard allows new concepts to be specified through the registration of new EDCS dictionary entries, their associated fields, and profiles.

New EDCS dictionary entries are registered using the established procedures specified in ISO/IEC 9973 as authorized by the International Registration Authority for Items¹⁾ and can be accessed at the International Register of Items. These procedures require the proposer to supply all information for a new EDCS dictionary entry except for its EDCS code. The International Register of Items shall assign the EDCS code and shall manage the EDCS code space. Other International Standards that normatively reference this International Standard, implementations of those standards, and implementations of this International Standard shall not use any EDCS code in the value ranges reserved for registration and/or future standardization by this International Standard with any meaning other than the one specified either in this International Standard or in the International Register of Items.

EDCS "items" as used in this International Standard refer to any of the standardized or registered EDCS dictionary entries, their associated fields, and profiles of EDCS. These are identified below.

Annex F defines a process for modification and deprecation of both standardized and registered EDCS items.

Clarification of standardized items, as described in ISO/IEC 9973, is not allowed by this International Standard. Clarification of registered items shall follow the procedures in ISO/IEC 9973.

The following types of EDCS dictionary entries may be registered, modified, clarified or deprecated:

1. EC,
2. EA,
3. EV,
4. EE,
5. EU,
6. EQ,
7. EO, and
8. EG.

The following associated fields may be registered, modified, clarified or deprecated independently, as appropriate:

1. references,
2. figures,
3. abbreviations used in definitions, and
4. abbreviations used in labels.

EDCS profiles may be registered, clarified or deprecated (see 10.16).

The guidelines that shall be followed in preparing proposals for registration and modification are specified in Clause 10. Proposals include required and optional information for each type of EDCS item, as well as accompanying administrative information (see Annex I). Proposals for deprecation of standardized or registered items, as well as proposals for clarification of registered items, shall also use the forms in Annex I.

4.16 Conformance

This International Standard specifies conformance of:

1. information coding specifications, applications, data models, and exchange formats that use EDCS labels, EDCS codes, and representations of EDCS attribute values;
2. applications that generate and/or read these exchange formats; and
3. language bindings that implement the EDCS application program interface.

The primary objectives of conformance are:

1. to promote interoperability by specifying specific subsets of this International Standard,
2. to promote consistent results among applications that use this International Standard,
3. to promote uniformity in the development of conformance tests, and
4. to facilitate automated test generation.

The conformance requirements are specified in Clause 11.

Conformance may be with respect to this entire International Standard, or with respect to a subset of it, as specified by a profile (see 4.13).

¹⁾ Contact information for the ISO-designated Registration Authority for Items registered under the ISO/IEC 9973 procedures is available at the ISO Maintenance Agencies and Registration Authorities web site: http://www.iso.org/iso/standards_development/maintenance_agencies.htm.

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