Environmental Data Coding Specification

4 Concepts

4.1 Introduction and table of contents

4.1.1 Table of contents

Table 4.1 -- Table of contents

Table 4.2 -- Table of tables

4.1.2 Overview

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

4.1.3 Acronyms

In this International Standard, acronyms 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 acronym for an EDCS dictionary, code, or label appears when the cursor is positioned over the acronym. The acronyms used in this International Standard are defined in Table 3.3 Abbreviated terms.

4.1.4 Capitalization

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

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

4.2 EDCS dictionary concepts

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

The nine EDCS dictionaries are:

6. EDCS Classification (EC) Dictionary,
7. EDCS Attribute (EA) Dictionary,
8. EDCS Attribute Value Characteristic (EV) Dictionary,
9. EDCS Attribute Enumerant (EE) Dictionary,
10. EDCS Unit (EU) Dictionary,
11. EDCS Unit Scale (ES) Dictionary,
12. EDCS Unit Equivalence Class (EQ) Dictionary,
13. EDCS Organizational Schema (EO) Dictionary, and
14. EDCS Group (EG) Dictionary.

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

15. For each entry in the EA Dictionary of EDCS attribute value type ENUMERATION (see 4.5.2 EDCS attribute value types), there is a set of entries in the EE Dictionary that specify the allowed values of that EA Dictionary entry.
16. 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 4.14 Registration).

4.3 Common concepts for EDCS dictionary entry fields

4.3.1 Definition

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

4.3.2 Label

The label field of an EDCS dictionary entry shall be a compact and human-readable designator that is used to denote a concept.  Labels in this International Standard may include the name or names for the 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 readable.

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.

4.3.3 Code

The code field of an EDCS dictionary entry shall be a compact and not necessarily human-readable designator that is used to denote a concept.

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 References and reference type

4.3.4.1 Introduction

Two broad types of references are recognized in International Standards. The first broad type of reference is a normative reference [ISOD2]. Identified provisions of a normative reference are incorporated by reference and "become" part of the subject standard. 4.3.4.2 Reference types specifies two forms of normative reference: the prescriptive reference and the authoritative reference. Normative references play a key role in ensuring the consistency of the body of International Standards by allowing work done by others to be reused without modification. The second broad type of reference is an informative reference [ISOD2]. Identified provisions of an informative reference are cited as being the source of, related to, or providing additional information about text in the subject standard, but the identified provisions of the document are not themselves directly incorporated into the subject standard. 4.3.4.2 Reference types specifies one restricted form of informative reference, the dictionary reference.

4.3.4.2 Reference types

Concepts in two documents may be related in several different ways. Two broad types of reference (normative and informative) are insufficient to capture all of the possibilities. Therefore, these two types of references are supplemented with the following refinements in this International Standard. The two-character acronym that denotes each type of reference is given in parenthesis following the name of the type of reference. In the following, a specification is a document that meets the requirements to be normatively referenced by an International Standard and the owner of such a specification is the organization responsible for maintaining the specification. The current edition of [ISOD2] may be consulted to determine if a specification is suitable for referencing from an International Standard.

1. Prescriptive reference (PR): The concept in this International Standard shall be the same concept as defined in a specification. The definition of the concept in this International Standard may be different from the definition in the specification because of modifications to:
   1. include missing (implied) context not present in the definition in the specification, or
   2. to match the style and structure of other definitions in this International Standard.
2. Authoritative reference (AR): The EDCS dictionary entry for a concept in this International Standard shall make a prescriptive reference to a concept in a specification and an agreement shall be established between the owner of this International Standard and the owner of the specification to ensure that the concept prescriptively referenced shall not be changed without the agreement of the owner of this (referencing) International Standard.
3. Dictionary reference (DR): The concept defined in this International Standard shall be defined by the meaning of the words used in the definition. This International Standard uses only the New Shorter Oxford English Dictionary [NSOED] as its dictionary for this purpose. Other dictionaries of the English language shall not be used. A specialized technical dictionary may be used as the reference, however the meaning of the words in the concept definition shall be determined by their definition in the NSOED, considering the context in which each word is used in the concept definition to choose the correct meaning of the word. In cases where a word can be used as more than one part of speech, a noun definition shall be used unless otherwise stated.
4. Informative reference (IR): The concept from this International Standard shall be defined in the same manner that a dictionary reference is defined, however a document other than a dictionary is referenced. An informative reference is appropriate if:
   1. it is not possible to provide either a prescriptive reference or an authoritative reference, and
   2. one or more documents exist that provide additional context that aid in understanding the concept from this International Standard.

The reference type field of an EDCS dictionary entry shall contain exactly one of the following values: PR, AR, DR, or IR. In some EDCS dictionaries, there is no reference type field because this information is captured as part of the definition of the EDCS dictionary.

An EE concept may be defined entirely by the use of an EC concept. In this case, no external references and reference type are necessary since the EDCS dictionary entry for the EC concept includes them. This case is represented in this International Standard by presenting such fields in grey to signify that the references and reference type are the same as those of the defining EC concept.

The references field of an EDCS dictionary entry shall contain one or more citations for that concept based on its reference type. Exactly one citation shall be specified for each EDCS dictionary entry whose reference type is PR, AR, or DR. One or more citations shall be provided for an EDCS dictionary entry whose reference type is IR.

The references and reference type fields for the EDCS dictionaries EC, EA, EE, and EG are specified in Annexes to this International Standard. The references and reference type fields for the EDCS dictionaries EV, EU, ES, EQ, and EO are specified in the main body of this International Standard.

4.3.4.3 Format and location of references

All references of reference type PR or AR shall be listed in 2 Normative references. All references of reference type DR or IR shall be shall be listed in either 2 Normative references or the Bibliography. All references listed either in 2 Normative references or in the Bibliography shall have a bibliographic citation in the format specified in [I690].

10.5 Guidelines for references for registered items specifies how references not included in this International Standard shall be included in registered items.

4.3.4.4 Citation format

Each citation consists of an identifier and an optional location enclosed in square brackets ( [ ] ) with the identifier listed first, followed by a comma, followed by the location. The identifier specifies the cited document and shall appear in either 2 Normative references or the Bibliography. The location specifies the portion of the document that is cited. Whenever possible, the location shall be specified in accordance with the requirements in [ISOD2]. When a cited document lacks a subclause structure, the location may be specified in a convenient and natural format depending on the organization of the cited document.

Examples: [I31-5, 5-28 a], [FACC, Annex A: AK120], and [S32, 3833].

If the reference type of an EDCS dictionary entry is DR, there are three alternative styles of citation:

1. If the words in the definition are to be interpreted according to the dictionary definition of each word considering the context in which the word is used, the citation shall be "[NSOED]". Since there is no specific dictionary entry being cited, the citation consists of only an identifier with no location.

2. If a dictionary entry contains a single part, then the location shall be the name of the dictionary entry. For example: [APDS, "Geiger counter"].

3. If a dictionary entry contains multiple parts, the format of the location shall include additional information. In such cases, the location in the citation shall be subdivided into two sub-fields, <word-or-term> and <definition-number>, and the citation for such a dictionary reference shall be of the form "[<identifier>, <word-or-term>, <definition-number>]". For example, if the concept attic is defined to be identical to the NSOED <word-or-term> "attic" with <definition-number> "B 2", the citation is "[NSOED, "attic", B 2]."

4.3.4.5 Selecting a reference type

The factors that shall be considered in determining which type of reference to use in preparing an EDCS dictionary entry include the following:

1. Based on practice and experience, some documents have refined and modified concepts from legacy documents as they are adapted for use in new domains of application. In this case an informative reference shall be made to the cited concept.
2. There are cases where the definition, and even the label or code, for a concept in one document is identical with that in another document. In this case, a prescriptive reference shall be made to the cited concept.
3. Some communities require that sets of concepts be designed with properties, including normality, that facilitate their use in data models and databases. Legacy concepts may therefore not be capable of direct reuse. In this case an informative reference shall be made to the cited concept.
4. Documents evolve over time. Documents evolve at different rates. This makes it difficult for one document to normatively reference another without coordination. Mitigation of these problems is the purpose of the concept of authoritative reference.

Each of the above factors limits the extent to which one document can normatively reference concepts directly from another document without modification.

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 definition,
2. a unique EDCS classification label (ECL),
3. a unique EDCS classification code (ECC),
4. a reference type, and
5. one or more references.

The EDCS Classification Dictionary is presented in 26 tables according to the letters of the alphabet (see Table 5.4). Each table consists of ECs with the same first character of their ECLs. Within each table, the ECs are ordered alphabetically by the ECL.

This International Standard shall not associate any EC with any EA(s), but it does provide for such associations in registered profiles (see 10.14 Guidelines for registration of EDCS profiles).

4.5 EDCS attributes

4.5.1 Introduction

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 4.5.2 EDCS attribute value types.) The values of EAs whose EDCS attribute value type is REAL (see Table 4.3) represent physical quantities (see 3.2.21 physical quantity). Therefore, these EAs have an associated EDCS unit equivalence class (see 4.10 EDCS unit equivalence classes) to characterize the physical quantity.

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

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

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

3. a unique definition,
4. a unique EDCS attribute label (EAL),
5. a unique EDCS attribute code (EAC),
6. a reference type,
7. one or more references,
8. an EDCS attribute value type, and
9. if the EDCS attribute value type is REAL, an EDCS unit equivalence class.

The EDCS Attribute Dictionary is presented in 26 tables according to the letters of the alphabet (see Table 6.4). Each table consists of EAs with the same first character of their EALs. Within each table, the EAs are ordered alphabetically by the EAL.

This International Standard shall not associate any EA with any other EA(s), but it does provide for such associations in registered profiles (see 10.14 Guidelines for registration of EDCS profiles).

4.5.2 EDCS attribute value types

Each EA shall have one of the EDCS attribute value types specified in Table 4.3.

Table 4.3 -- EDCS attribute value types

This International Standard provides context information with each STRING. This information specifies 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 String).

Each EA instance of EDCS attribute value type REAL, INTEGER, or COUNT shall have an associated EDCS numeric value type. The EDCS numeric value types specified in Table 4.4 determine whether the values of an EA instance are a single number or an interval of numbers.

Table 4.4 -- EDCS numeric value types

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). An EDCS Attribute Value Characteristic Dictionary entry specifies information concerning the values of EAs. Within the scope of the EDCS Attribute Value Characteristic Dictionary, each EV shall have:

1. a unique definition,
2. a unique EDCS attribute value characteristic label (EVL),
3. a unique EDCS attribute value characteristic code (EVC),
4. a description of which EDCS attribute value types it may apply to,
5. a reference type, and
6. one or more references.

The EDCS Attribute Value Characteristic Dictionary is presented in two tables. The first table defines quantitative attribute value characteristics and the second table defines qualitative attribute value characteristics. Each table presents EVs in a natural order.

This International Standard shall not associate any EV with any EA(s), but it does provide for such associations in registered profiles (see 10.14 Guidelines for registration of EDCS profiles).

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 an element 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 definition,
2. a unique EDCS attribute enumerant label (EEL),
3. a unique EDCS attribute enumerant code (EEC),
4. a reference type, and
5. zero or more references.

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 26 tables according to the letters of the alphabet (see Table 6.35). Each table consists of EAs with the same first character of their EALs, however, only EAs whose EDCS attribute value type is ENUMERATION are included. Within each table, the EAs are ordered alphabetically by their EALs, 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 defined in [I31]. Where possible, units of measure used in this International Standard are taken from, or derived from, those defined in [I31].

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

1. a unique definition,
2. a unique EDCS unit label (EUL),
3. a unique EDCS unit code (EUC),
4. an optional symbol,
5. a physical quantity,
6. an EDCS unit equivalence class (see 4.10 EDCS unit equivalence classes),
7. a reference type, and
8. one or more references.

The EDCS Unit Dictionary is presented in four tables: two tables of EUs derived from SI (ordered alphabetically by EUL), one table of EUs outside the scope of SI, and one table of deprecated EUs (see Table 7.4 and Table B.1). 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 provides scaling information for use in conjunction with EUs. Some units of measure for the same physical quantity may be converted from one to the other by means of a linear equation. When the multiplicative constant (scale factor) in that linear equation is one from a list of certain powers of ten or 2¹⁰ (and the additive constant is zero), this International Standard specifically treats them as EDCS unit scales.

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

1. a unique definition,
2. a unique EDCS unit scale label (ESL),
3. a unique EDCS unit scale code (ESC),
4. a symbol,
5. a reference type, and
6. one reference.

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 units of measure that are equivalent in the sense that they characterize the same physical quantity.

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

1. a unique definition,
2. a unique EDCS unit equivalence class label (EQL),
3. a unique EDCS unit equivalence class code (EQC),
4. a list of EU members,
5. a reference type, and
6. one reference.

The EDCS Unit Equivalence Class Dictionary is presented in three tables (ordered alphabetically by 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 EDCS organizational schema.

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

1. a unique definition,
2. a unique EDCS organizational schema label (EOL),
3. a unique EDCS organizational schema code (EOC),
4. a reference type, and
5. one or more references.

The EDCS Organizational Schema Dictionary is presented in a table (see Table 8.4). Within that table, the EOs are ordered alphabetically by the EOL.

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 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 EG shall have:

1. a unique definition,
2. a unique EDCS group label (EGL),
3. a unique EDCS group code (EGC),
4. a reference type, and
5. one or more references.

The EDCS Group Dictionary is presented in a table (see Table 8.6). Within that table, the EOs are ordered alphabetically by EOL, with each EO followed by its associated EGs. The EGs for each EO are ordered alphabetically by the EGL.

4.13 EDCS application program interface

This International Standard specifies an EDCS application program interface.  This EDCS application program interface consists of two functions: one function to convert between EDCS attribute values of EDCS attribute value type REAL given with respect to different EUs and/or ESs and another 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 characterize the same physical quantity, with each ES most appropriate for some application. Therefore, applications may need to convert a value measured with respect to an EU and ES to a value measured 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 4.14 Registration). An implementation may or may not support all standardized 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.  It also specifies a set of abstract data types that are used to specify the concepts in this International Standard.

4.14 Registration

This International Standard allows new concepts to be defined by registration of new EDCS dictionary entries. Registration shall not be used to modify any existing standardized or registered EDCS dictionary entry. New EDCS dictionary entries are registered using the established procedures of the ISO International Registration Authority for Graphical Items ¹⁾. These procedures require the proposer to supply all information for a new EDCS dictionary entry except for its EDCS code.  The EDCS code shall be assigned, and the EDCS code space managed, by the ISO International Registration Authority for Graphical Items. 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 or future standardization by this International Standard with any meaning other than the one defined in this International Standard or in the International Register of Graphical Items. Registration shall be according to the procedures in [I9973].

The following types of EDCS dictionary entries may be registered:

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

In addition, EDCS profiles may also be registered (see 10.14 Guidelines for registration of EDCS profiles).

The guidelines that shall be followed in preparing registration proposals are specified in 10 Registration. Registration proposals include required information for each type of EDCS dictionary entry, as well as accompanying administrative information.

4.15 Conformance

Because the scope of this International Standard is broad in order to meet the requirements of many different applications, a mechanism is needed to specify subsets and choose options that are tailored to particular purposes. This International Standard uses profiles for this purpose. 10.14 Guidelines for registration of EDCS profiles defines the concept of a profile.

This International Standard specifies conformance of:

1. 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:

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

1) At the time this International Standard was published, the ISO International Registration Authority for Graphical Items was the United States National Imagery and Mapping Agency (NIMA). The mailing address was: Registration Authority, National Imagery and Mapping Agency, c/o Joint Interoperability Test Command, Building 57305, Room 263A, Fort Huachuca, Arizona 85613-7020. USA.

http://www.iso.ch/iso/en/ittf/PubliclyAvailableStandards/ISO_IEC_18025_Ed1.html