Environmental Data Coding Specification

4 Concepts

4.1 Introduction and table of contents

4.1.1 Table of contents

See Table 4.1 for the table of contents for this clause.

Table 4.1 -- Table of contents

4.1.2 Overview

This International Standard supports the encoding and communication of qualitative and quantitative information associated with physical environments, both real world and artificial. This is accomplished by specifying a collection of eight EDCS Dictionaries of environmental concepts. An EDCS Dictionary is a list of EDCS Dictionary Entries each of which describes a single concept. Each EDCS Dictionary contains entries of a similar nature, however each entry is unique.  Each EDCS Dictionary Entry consists of the following fields:

1. the definition,
2. the label,
3. the code,
4. references and reference types, and
5. other EDCS Dictionary-dependent information such as value types, unit symbols, unit equivalence classes or related concepts.

The eight EDCS Dictionaries are:

6. EDCS Classification Dictionary
7. EDCS Attribute Dictionary
8. EDCS Attribute Enumerant Dictionary
9. EDCS Unit Dictionary
10. EDCS Unit Scale Dictionary
11. EDCS Unit Equivalence Class Dictionary
12. EDCS Organizational Schema Dictionary
13. EDCS Group Dictionary

Additional entries may be added to most EDCS Dictionaries through the process of registration.

The EDCS Unit Conversion Application Program Interface supports conversion between numeric values given in different units of measure.

4.2 Common concepts for EDCS Dictionary Entry fields

4.2.1 Definitions

The definition field of an EDCS Dictionary Entry is a precise statement of the nature, properties, scope or essential qualities of the concept embodied in the entry.  Definitions in this International Standard are concise and references are used whenever necessary to provide more extensive specifications of the concept being described.

4.2.2 Labels

In applications such as data object interchange, there is a requirement for compact and human-readable designators that can be used to refer to environmental concepts. This International Standard calls the designators defined for this purpose labels.

Humans assign names for the purpose of designation. Names are given to concepts for many different purposes. These include:

1. classificatory: e.g., Linnaean systematic taxonomies;
2. functional: e.g., computer, traffic signal, telephone, writer;
3. descriptive: e.g., supraorbital, pepper box, exotoxin;
4. acronyms: e.g., LASER, CD-ROM;
5. social: e.g., titles, surnames; and
6. arbitrary: e.g., tab, mug.

In general, names are not unique. They form classes of equivalent names called synonyms. One concept may have many different names given to it for different purposes. The converse is also true as the same name might identify different concepts. 

The four requirements for labels in this International Standard are:

7. each label uniquely denotes a concept,
8. each label is a succinct expression of the concept it denotes, 
9. labels are represented as character strings, and
10. labels are human readable.

4.2.3 Codes

In applications such as data object interchange, there is a requirement for compact and not necessarily human-readable designators that can be used to refer to environmental concepts.  This International Standard calls the designators defined for this purpose codes.

The three requirements for codes in this International Standard are:

1. each code uniquely denotes a concept, 
2. codes are represented as integers, and
3. codes are assigned sequentially in increasing order beginning at 1.

A label and a code may be used interchangeably to designate the same concept.

4.2.4 References

4.2.4.1 Introduction

Annexes in this International Standard provide external references for EDCS Classifications, EDCS Attributes, EDCS Attribute Enumerants and the groups in the EDCS General Organizational Schema. In addition to normative and informative references, this International Standard defines additional types of references based upon defined relationships between the specifying and the specified documents and their respective owners. The goal is to permit the highest possible degree of interoperation among applications that use coded elements defined by different communities including ISO/IEC, DGIWG, IHO, WMO and the SEDRIS Organization.

4.2.4.2 Background

Two broad types of references are recognized in International Standards. The first of these is the normative reference where identified provisions of some external document are incorporated by reference and "become" part of the subject standard. The second is an informative reference in which an external document is cited as being the source of, or related to, text in an International Standard but the identified provisions of the external document are not themselves directly incorporated into the subject standard. Normative references play a key role in insuring the consistency of the body of International Standards by allowing work done by others to be re-used without modification.

In environmental data specification, determining which type of external reference to make is a complex issue. The factors that bear on this decision include:

1. The degree of specificity of concepts and definitions defined in various documents varies widely. Some specifications are compromises and do not themselves define some concepts and definitions precisely enough for direct use. Instead, users of these specifications develop product-specific specifications that define how the concepts and definitions are used in particular products they produce. 
2. Some specifications have developed advanced sets of concepts and definitions that solve or avoid problems with legacy specifications. For example, in modelling and simulation, the units of measure and scale used to qualify a numeric value are separated from the specification of the attribute. In other areas, attribute specifications include units of measure and scale in the attribute specification itself.
3. Based on practice and experience, some specifications have further refined and modified concepts and definitions from legacy specifications, as they are adapted for use in new domains of application.
4. There are cases where the definition and even the label or code for a concept in one specification is identical with that in another specification.
5. Some communities require that concepts be designed with properties, including normality, that facilitate their use in data models and data bases. Many legacy concepts cannot be directly used in new applications because they were not well designed.
6. Specifications evolve over time. Specifications evolve at different rates. This makes it difficult for one specification to normatively reference another without some agreement between the specification owners.

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

In case a concept from one specification cannot be used directly without modification, an additional consideration is whether the manner in which one concept is based on, or derived from, another can or should be specified. This again is a complex issue with at least the following factors bearing on a choice of strategy for how such "concept mappings" might be specified:

7. The direction of the mapping is often application dependent. For example, modelling and simulation applications consume datasets from geographic information providers (such as national mapping agencies) but rarely provide datasets back to such information providers.
8. Mappings are often application and even dataset dependent. As described in 4.2.4.2 (a), concepts are applied in different "products" in different ways based on "product production rules." Therefore, for example, the mapping of a dataset of type A into an application will map concept X using different rules than those if concept X was from a dataset of type B.
9. Because mappings may be dataset specific and also since they may vary over time to accommodate changes in coding specifications and products, they may be best specified in documents other than International Standards.
10. A single concept used in one specification might map to multiple concepts (or even concepts of different types) in another specification.

4.2.4.3 Types of references

There are many ways that concepts in two specifications can be related. Two types of reference (normative and informative) are insufficient to capture all the possibilities. Therefore, these two types of references are supplemented with the following refinements in this International Standard. The two character notation used for each type of reference is given in parenthesis following the name of the type of reference. This notation is used in the reference type field of EDCS Dictionary Entries.

1. Authoritative reference (AR): A concept in this International Standard normatively references a concept from another specification under the following additional conditions:
1. The definition from the authoritative specification is copied verbatim into this (referencing) International Standard.
2. An agreement is established between the owners of the two specifications to insure that the owner of the specification whose concept is authoritatively referenced will not change that concept without the agreement of the owner of this (referencing) International Standard.
2. Normative reference (NR): A concept in this International Standard normatively references a concept from another specification with no additional conditions.
3. Qualified reference (QR): A concept  in this International Standard normatively references a concept from another specification under the following additional conditions.
1. The concept is defined differently in this (referencing) International Standard.
2. The relationship between the two concepts is specified in this (referencing) International Standard.
4. Informative reference (IR): A concept from this International Standard is related to, or derived from, a concept from another specification but the relationship is not stated.
5. Authoritative definition (AD): The owner of this International Standard recognizes itself as an authoritative source for the definition of the concept, and not, for example, the label or code associated with the concept. A reference to a concept in another specification may be included if that concept is similar to the authoritatively defined concept in this International Standard.
6. Non-referenced definition (ND): The definition of a concept in this International Standard is self-explanatory based on the dictionary meaning of the words that form the definition. Therefore no external reference is included.
7. Un-referenced definition (UD): This International Standard includes concepts for which there is no satisfactory authoritative, normative or qualified reference available This International Standard defines the concept, even though the owner of this International Standard does not recognize itself as the authoritative source for such a concept. A reference to a concept in another specification may be included if that concept is similar to the un-referenced concept in this International Standard.  Other International Standards should not make an authoritative, normative or qualified reference to an un-referenced definition in this International Standard.

4.2.5 Related concepts

Concepts in the EC, EA or EE  Dictionaries may be related to other concepts in the EC, EA or EE  Dictionaries. Related concepts are identified by providing a list of the labels of other EDCS Dictionary Entries whose concepts are related to the one being defined in one of two ways: 

1. because they are similar, or 
2. because they are exact or approximate opposites.

4.3 EDCS Classifications

This International Standard uses EDCS Classifications (ECs) to specify the type of environmental objects.  Each EC has a unique definition, and is designated by both a unique EDCS Classification Label (ECL) and a unique EDCS Classification Code (ECC). The EDCS Classification Dictionary is presented in tables with the EDCS Dictionary Entries grouped alphabetically by the first letter of the ECL. This International Standard does not associate any EC with any EA(s).

4.4 EDCS Attributes

4.4.1 Introduction

This International Standard uses EDCS Attributes (EAs) to describe the state of environmental objects. Each EA has a unique definition, and is designated by both a unique EDCS Attribute Label (EAL) and a unique EDCS Attribute Code (EAC). Each EA has an EDCS Attribute Value Type and may have an associated EDCS Unit Equivalence Class.   The EDCS Attribute Dictionary is presented in tables with the EDCS Dictionary Entries grouped alphabetically by the first letter of the EAL. This International Standard does not associate any EA with any EC(s).

4.4.2 EDCS Attribute Value Types and EDCS Storage Types

Each EDCS Attribute shall have one of the EDCS Attribute Value Types specified in Table 4.2.  In addition to these EDCS Attribute Value Types, this International Standard also defines a set of EDCS Storage Types that may be used to specify how instances of EDCS Attribute Value Types are to be represented for purposes of interchange.

Table 4.2 -- EDCS Attribute Value Types and EDCS Storage Types

4.5 EDCS Attribute Enumerants

4.5.1 Introduction

For each EA whose EDCS Attribute Value Type is ENUMERATION, this International Standard defines the elements of the set of  values of that EA as EDCS Attribute Enumerants (EEs). Each set of EEs is associated with exactly one EA.  Therefore, an EE does not stand alone, but must be interpreted within the context of the EA with which it is associated.  

Each EE has a definition, and is designated by both an EDCS Attribute Enumerant Label (EEL) and an EDCS Attribute Enumerant Code (EEC).  The definition, EEL and EEC are unique only within the context of that EA. The EDCS Attribute Enumerant Dictionary is presented in tables with the EDCS Dictionary Entries grouped alphabetically by the first letter of the corresponding EAL.

EEs are divided into two categories:

1. those EEs that represent concepts unique to individual EAs;

2. those EEs that represent concepts common to all EAs and accordingly are pre-specified because their definitions, EELs and EECs can be shared throughout the EDCS Attribute Enumerant Dictionary.

4.5.2 Pre-specified EDCS Attribute Enumerants

There are EEs that are identically specified for every attribute whose EDCS Attribute Value Type is ENUMERATION, LOGICAL or NULL. These identically specified EEs are listed in Table 4.3. These specifications are to be applied in the context of a functional interface where an  EC and an EA are given and the function is expected to return a single EE from the set of valid EEs for that EA. Under some conditions, a single EE unique to that EA cannot be returned, and one of these pre-specified EDCS Attribute Enumerants shall be returned instead.

Table 4.3 -- Pre-specified EDCS Attribute Enumerants

EDCS Attribute Enumerant Codes for other EDCS Attribute Enumerants are assigned INTEGER values starting at 11 and increasing sequentially in numerical order.

4.6 EDCS Units

This International Standard uses EDCS Units (EUs) to characterize the values of physical quantities in conformance to the International System of Units (SI) as defined in ISO 31:1994. Where possible, units of measure used in this International Standard are taken from or derived from those defined in ISO 31:1994. Each EU has a unique definition, and is designated by both a unique EDCS Unit Label (EUL) and a unique EDCS Unit Code (EUC). EUs are further characterized a symbol and by membership in a class of equivalent units called an EDCS Unit Equivalence Class (EQ). The EDCS Units Dictionary is presented in tables with the EDCS Dictionary Entries grouped alphabetically by the first letter of the EUL. 

4.7 EDCS Unit Scales

This International Standard uses EDCS Unit Scales (ESs) to provide scaling information for use in conjunction with EUs. Some units of measure for the same physical quantity can be converted one to the other by means of a linear equation. When the multiplicative constant (scale factor) in that linear equation is a certain power of ten or 2¹⁰ (and the additive constant is zero), this International Standard specifically treats them as EDCS Unit Scales (ESs). 

Each ES has a unique definition, and is designated by both a unique EDCS Unit Scale Label (ESL) and a unique EDCS Unit Scale Code (ESC). The EDCS Unit Scale Dictionary is presented in tables with the EDCS Dictionary Entries organized by the value of the multiplicative constant (scale factor). 

4.8 EDCS Unit Equivalence Classes

This International Standard defines EDCS Unit Equivalence Classes (EQs), which are sets of units of measure that are equivalent in the sense that they characterize the same physical quantity.  Each EQ has a unique definition, and is designated by both a unique EDCS Unit Equivalence Class Label (EQL) and a unique EDCS Unit Equivalence Class Code (EUC). The EDCS Unit Equivalence Class Dictionary is presented in tables with the EDCS Dictionary Entries grouped alphabetically by the first letter of the EQL.

4.9 EDCS Organizational Schema

This International Standard uses EDCS Organizational Schema (EOs) to arrange ECs and EAs into sets based on similarity.  The sets need not be disjoint. An EDCS Organizational Schema (EO) is the end result of a process of classification and consists of a set of EDCS Groups (EGs).  In general, no further organization shall be required among the EGs in an EO. In particular, 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, the EO is called complete.  All EOs in this International Standard shall be complete. 

Each EO has a unique definition, and is designated by both a unique EDCS Organizational Schema Label (EOL) and a unique EDCS Organizational Schema Code (EOC). The EDCS Organizational Schema Dictionary is presented in tables with the EDCS Dictionary Entries grouped alphabetically by the first letter of the EOL.

4.10 EDCS Groups

This International Standard uses EDCS Groups (EGs) to collect similar ECs and EAs.  The concepts in an EG are called members of the EG. Each EG  has a unique definition, and is designated by both a unique EDCS Group Label (EGL) and a unique EDCS Group Code (EGC). The EDCS Group Dictionary is presented in tables with the EDCS Dictionary Entries grouped alphabetically for each EO by the first letter of the EGL.

4.11 EDCS Unit Conversion

This International Standard defines a EDCS Unit Conversion Application Program Interface to convert between values given with respect to different EUs and ESs. 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 a EU and an ES to a value measured with respect to a different EU and ES.  The EDCS Unit Conversion Application Program Interface defines data types and functions for conversion between values given with respect to different EUs and ESs.

4.12 Conformance

This International Standard defines conformance for exchange formats that incorporate EDCS labels or codes and for language bindings that implement the EDCS Units Conversions API.  The concept of an EDCS Profile is introduced to allow useful subsets of the EDCS Dictionaries to be specified.  Conformance is defined only in the context of such a profile.

4.13 Registration

4.13.1 Introduction

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 code.  The code is assigned and the 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 code in the value ranges reserved for registration by this International Standard with any meaning other than the one defined in the International Register of Graphical Items. Registration shall be according to the procedures in ISO/IEC 9973:1994, Procedures for registration of graphical items.

The following types of EDCS Dictionary Entries may be registered:

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

In addition, EDCS Profiles may be registered.

The following subclauses state the guidelines to be followed in preparing registration proposals, including how definitions and labels are to be created.

4.13.2 Guidelines for definitions for registered items

The definitions in this International Standard were created by applying a set of guidelines. These guidelines shall be applied when creating definitions for proposed registered EDCS Dictionary Entries.

Definitions shall be developed based on the following guidelines:

1. A definition shall be provided for each EDCS Dictionary Entry.  This definition shall contain at least one word, number, expression or formula.
2. Definitions shall be clear and concise, containing only the content necessary to express the concept.
3. Complete sentences shall be used except when a single word or phrase is unambiguous. 
4. A single sentence shall be used except when multiple sentences are necessary to add significantly to the clarity and completeness of the definition.
5. Definitions shall be unambiguous and worded to clearly express a single concept.
6. Where a set is being defined, the phrase "a set of" shall be used (e.g., "a set of indicator lights").
7. Jargon shall not be used.
8. Abbreviations shall not be used.
9. Acronyms may only be used if they have been defined in Table 3.2 Acronyms.
10. If an acronym has been defined in Table 3.2 Acronyms then it shall be used wherever the phrase would have appeared. That is, the phrase shall not be used except in Table 3.2 Acronyms; wherever the phrase might have appeared, the acronym shall be used instead.
11. No units of measure shall be abbreviated.
12. Unit symbols shall not be used (e.g., use "metres per second", instead of "m/s").
13. References shall not be embedded in definitions with one exception. Where a reference is used not as the source of a definition, but rather to define the format of an EA whose EDCS Attribute Value Type is STRING, that reference may be part of the definition.
14. Definitions shall be atomic, self-contained and independent of all other  EDCS Dictionary Entries in the same EDCS Dictionary with one exception. A definition may intentionally express a composite of other concepts, if those concepts are individually defined within the same EDCS Dictionary.
15. When a composite concept is defined (that is, the concept is the union of other, more primitive concepts in the same EDCS Dictionary), the definition shall be a clear and concise integration of the definitions of the other concepts. In this case, an additional sentence identifying the more primitive concepts shall be included.
16. Definitions shall be unique within the same EDCS Dictionary.
17. Units of measure should not be used in EC EDCS Dictionary Entries.
18. Units of measure shall not be used in ES, EQ, EO, or EG EDCS Dictionary Entries.

4.13.3 Guidelines for constructing labels for registered items

The labels in this International Standard were created by applying a set of guidelines. These guidelines shall be applied when creating labels for proposed  registered EDCS Dictionary Entries. 

Labels shall be developed based on the following guidelines:

1. A label shall be associated with each EDCS Dictionary Entry.
2. Labels shall be character strings.
3. Labels shall begin with an alphabetic character (and therefore labels shall contain at least one character).
4. Labels shall contain only uppercase characters (A-Z) with two exceptions:
1. relational operators ("gt", "lt", "ge", "le", "eq", and "ne"); and 
2. the radix symbol "r".
5. Labels may be a single word or may be composed of a series of components each of which is a word, an abbreviation, or an acronym.
6. Labels should be as short as possible while capturing a common use descriptive word or phrase representative of the concept.
7. The length of a label shall not exceed fifty-nine (59) characters.
8. The initial characters of each label shall be unique within the set of all EDCS Dictionaries in the following manner:
1. EALs shall be unique within the set of EALs of the same EA (i.e., the same label could also be used for an EE of a different EA).
2. All other labels shall be unique within the set of labels in their EDCS Dictionary.
3. EELs shall be unique in the first nineteen (19) characters.
4. EGLs shall be unique within the first twenty-three (23) characters.
5. All other labels shall be unique in the first twenty-seven (27) characters.

The components of a label shall be chosen according to the following guidelines:

9. The underscore (_) character shall be used to concatenate the components of a label.
10. Labels shall not contain spaces.
11. The order of the components in a label shall be in the natural order in which the components are likely to be used within an English phrase.
12. Components of labels shall not be used with a different meaning from how that component is used in this International Standard or in previously registered EDCS Dictionary Entries.
13. Verbs, articles, conjunctions, negations, and prepositions shall not be used as components of a label except where required for clarity.
14. EGLs shall be nouns possibly modified by adjectives.
15. Whenever possible, components of labels shall be taken from Annex H. Abbreviations and acronyms used in the construction of labels.

Recognized abbreviations  for words and acronyms for phrases may be used as components of a label based on the following guidelines:

16. Each abbreviation shall uniquely represent a single word.
17. A single abbreviation shall not represent a combination of words.
18. Each acronym shall uniquely represent a single multi-word phrase.
19. If a word is abbreviated in one label, it is not required to be abbreviated in other labels.
20. If a word is abbreviated in one label, the same abbreviation should be used wherever that word is abbreviated.
21. If a phrase is replaced by an acronym in one label, it is not required to be replaced in other labels.
22. If a phrase is replaced by an acronym in one label, the same acronym should be used wherever that phrase is intended.
23. Within a set of EEs, abbreviations shall be used consistently across all EELs (i.e., either a term is always abbreviated, or never abbreviated).
24. New acronyms may be defined if necessary to create a label whose length meets the criteria defined in (f) and (g).
25. Jargon shall not be used.
26. An acronym or abbreviation in a label shall not be, by itself, a word with a different meaning than that of the word/phrase that it replaces.  For example, the acronym LOST should not be used for the phrase "Line of Sight Type".

Units of measure or abbreviations for units of measure shall not be used as components of labels with three exceptions:

27. Labels of EDCS Units,
28. Labels of EDCS Attribute Enumerants, and
29. Labels in which the unit of measure or its abbreviation is not used as a unit of measure such as "TESLA_COIL" or "METRE_STICK."

4.13.4 Rules for assigning codes for registered items

Codes not assigned in this International Standard are reserved for future standardization or for registration. For each EDCS Dictionary, Table 4.4 specifies the ranges for codes reserved for these purposes.

Table 4.4 -- Reserved code ranges

Codes shall be assigned by the ISO International Registration Authority for Graphical Items following these rules:

1. Nothing should be assumed about the relationship among EDCS Dictionary Entries from the numerical relationships of their corresponding codes. For example, the numerical sequencing of codes does not impose any sequential ordering to the concepts denoted by those codes.
2. Integer indices are used for codes even though only positive values shall ever be assigned in either this International Standard or through registration. This allows negative values to be used experimentally in applications even though such use of negative codes is not in conformance to this International Standard.
3. Code values reserved for future standardization shall not be assigned by the Registration Authority for Graphical Items.
4. The Registration Authority for Graphical Items shall assign codes in increasing order beginning at the first code in the set of codes reserved for registration within each set of codes.

4.13.5 Guidelines for related concepts for registered items

The lists of related concepts for EDCS Dictionary Entries in this International Standard were created by applying a set of guidelines. These guidelines shall be applied when creating lists of related concepts for proposed registered EDCS Dictionary Entries. 

Lists of related concepts shall be developed according to the following guidelines:

1. Concepts in the EC, EA or EE  Dictionaries may be related to other concepts in the EC, EA or EE  Dictionaries.
2. Related concepts shall be identified by providing a list of the ECLs, EALs or EELs of other EDCS Dictionary Entries whose concepts are related to the one being defined in one of two ways: 
1. because they are similar, or 
2. because they are exact or approximate opposites.
3. Each ECL, EAL or EEL in the list of related concepts shall be preceded by a two character designator identifying the EDCS Dictionary in which the related concept is located:  EC, EA or EE  for the EDCS Classification, EDCS Attribute, and EDCS Attribute Enumerant Dictionary Entries, respectively.
4. The pairs of two character designators and labels shall be separated from each other by commas.
5. The list of pairs (two character designators and labels) in the list of related concepts shall be presented in alphabetic order.

4.13.6 Guidelines for references for registered items

The following guidelines shall be applied when creating references for proposed registered EDCS Dictionary Entries:

1. Each proposed registered item shall identify one or more references, except for concepts whose definitions stand alone based on the dictionary meaning of the words composing the definition (see 4.2.4.3 Types of references, Non-referenced definition).
2. If more than one reference is provided, then all references shall be informative references.
3. The reference type shall be identified as one of the categories defined in 4.5.3 Types of references.
4. Additional reference information shall be supplied as required by the reference type.

4.13.7 Guidelines for registration of EEs

The following guidelines apply to the registration of EEs:

1. Definitions of EEs shall not repeat any portion of the definition of the corresponding EA. For example, an EA whose definition is "The function of a building" shall not have an EE whose definition is "An administrative building".
2. EEs of different EAs may have identical definitions. 
3. When EE definitions are intended to be shared between different EAs, the shared definition shall be so indicated.
4. No unit of measure that has been identified in Annex B shall be used with the following two exceptions:
1. When a unit appearing in Annex B is needed to ensure clarity for a community of EDCS users, it shall appear in parentheses following a unit of measure that is consistent with an entry in the EDCS Unit Dictionary, e.g., "12,2 metres (40 feet)". 
2. The use of the term "approximately" associated with the value and deprecated unit of measure within parentheses is acceptable, but not necessary, e.g., "12,2 metres (approximately 40 feet)".
5. Units of measure may be used in EDCS Attribute Dictionary Entries, where they are used to specify the conditions under which an attribute value pertains, but this use should be avoided where possible.
6. Terms appearing in units of measure may be used in definitions where appropriate (e.g., "Tesla coil" and "metre stick").
7. If the EDCS Attribute Value Type of an EA is ENUMERATION then at least one new EE corresponding to that EA shall also be registered. If a set of EEs corresponding to the same EA are registered at the same time, then the EEs shall be listed in a convenient natural or conventional order.
8. If the EDCS Attribute Value Type of an EA is INTEGER or REAL, then if the EQ appropriate for the specification of the values of the EA is not previously defined in this International Standard or by registration, then at least one new EQ and if necessary one new EU that is a member of that EQ shall also be registered.

4.13.8 Guidelines for registration of EUs

The following guidelines apply to the registration of EUs:

1. Entries in the EDCS Unit Dictionary should be derived in accordance with ISO 31 (e.g., quantities, multiplication, division and logarithms) and the entries in the Symbol and Quantity / Definition fields should reflect this.
2. Entries in the EDCS Unit Dictionary incorporating the symbols for EDCS Unit Scales are acceptable, however:
1. If a "pure" equivalent non-scaled unit of measure is not already an EU, then it shall be registered. The EQC for the newly registered non-scaled unit of measure shall be used as the EQC for the newly registered scaled unit of measure.
2. The EU should be defined in terms of the "pure" non-scaled unit of measure by including an equation of the general form "<scale definition><non-scaled unit symbol>".
3. The EU's symbol should include the symbols for the scaled unit(s), as appropriate.
3. If no standardized or registered EQC is appropriate for the EU being registered, then a new EQ shall also be registered.

4.13.9 Guidelines for registration of EOs and EGs

No rules apply uniquely to the registration of EOs and their EGs.

4.13.10 Guidelines for registration of EDCS Profiles

The following guidelines apply to the registration of EDCS Profiles:

1. An EDCS Profile shall specify a subset of this International Standard and its registered items as:
1. a list of EDCS Dictionaries,
2. for each listed EDCS Dictionary, a list of entries in that dictionary, and
3. optional EDCS Dictionary Entry Association Rules, each of which specifies a required relationship between two EDCS Dictionary Entries.
2. The optional EDCS Dictionary Entry Association Rules may include:
1. for each EDCS Classification Dictionary Entry listed in the Registered EDCS Profile, a rule specifying the EDCS Attribute Dictionary Entries that may be associated with that EDCS Classification Dictionary Entry and those that are required to be associated with that EDCS Classification Dictionary Entry;
2. for each EDCS Attribute Dictionary Entry listed in the Registered EDCS Profile, a rule specifying any restricted range of the values of the Attribute or restricted EQ label values;
3. for each EDCS Attribute Dictionary Entry listed in the Registered EDCS Profile, any subset restrictions on the EDCS Attribute Enumerant Dictionary Entries that are associated with that EDCS Attribute Dictionary Entry;
4. each occurrence of EDCS Dictionary Entry A requires at a specified number of occurrences of EDCS Dictionary Entry B;
5. the value of field X in EDCS Dictionary Entry A requires a specified value in field Y of EDCS Dictionary Entry B; and
6. precise statements of any additional rules (often called "business rules") that specify relationships among the EDCS Dictionary Entries in the profile.

Editors' Note: The concept of EDCS Dictionary Entry Association Rule needs review and requires further elaboration. In addition,: this response from Stuttgart is not yet implemented: "We should investigate leveraging the structure of 19110 and/or 19106, where appropriate, and investigate whether we specifically want to require "a 19110 compliant catalogue" as the mechanism for defining an EDCS profile and in particular EDCS Dictionary Entry association rules."

Another Editor's Note: The EDCS Dictionary Entry Association Rules should be expanded to includes rules about EDCS Dictionaries (such as no EDCS Unit Dictionary entries shall be used) as well as rules about  EDCS Dictionary entry fields (the values of the EA FARMING_TYPE are restricted to EE CHICKEN and EE TURKEY), and rules about EDCS Dictionary Entries (the EC LIGHTHOUSE shall not be used.)  The name "EDCS Dictionary Entry" needs to  broadened to indicate the full scope.

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.sedris.org/Specifications/EDCS/index.html