Lois FrittsLois FrittsSystems Development CenterSystems Development Center

February 16, 1999

SDC-0055-057-JE-8022

SDC-0055-057-JE-8022

Challenges

Data element definitions and descriptions are often not sufficient to support reuse or multiple users of data

Data element names are often not definitive for value domains

Data standardization must focus on data element definitions rather than names

SDC-0055-057-JE-8022

Purpose of Definitions

The purpose of a data element definition is to

define a data element with words or phrases that

describe, explain, or make definite and clear its

meaning.

SDC-0055-057-JE-8022

Data Definition Rules

A data definition shall be:

Unique

Singular

State the concept, not its negative

Descriptive phrase or sentence

Commonly understood abbreviations

Without embedded definitions

SDC-0055-057-JE-8022

Distinguishable from every other definition within the registry

Good - The date when a regulation became effective.The date when collection of the sample began.

Poor - The date when the event started.

Unique

SDC-0055-057-JE-8022

Singular

Always expressed in the singular

Good - The unique identification number assigned

to a facility.

Poor - Unique identification numbers assigned

to facilities.

SDC-0055-057-JE-8022

Positive, Not Negative

Cannot exclusively say what it is not

Good -A city that is included in a county division.

Poor -A city that does not itself represent acounty division.

SDC-0055-057-JE-8022

Descriptive

Include the essential characteristics of the concept

Good -The name of the individual designated to

be the facility’s representative for communications about the facility.

Poor -Person to contact.

SDC-0055-057-JE-8022

Avoid Abbreviations

Use only commonly known abbreviations

Good -The Standard Industrial Classification (SIC) code that represents the economic activity of a company.

Poor -The SIC code that represents the economic activity of a company.

SDC-0055-057-JE-8022

No Embedded Definitions

Second concept should not appear in the definition

Good -The text that describes the method used to

calibrate an instrument.

Poor - The text that describes the method used to

calibrate an instrument. Calibration is the process of rectifying the graduation of quantitative instruments.

SDC-0055-057-JE-8022

Data Definition Guidelines

State the essential meaning of the concept Be precise and unambiguous Be concise Be able to stand alone Be expressed without embedding rationale,

functional usage, domain information or procedural information

Avoid circular reasoning Use consistent terminology and structure for

related definitions

SDC-0055-057-JE-8022

Essential Meaning

Avoid non-essential characteristics

Good -The name of a country where mail is delivered.

Poor -The last line of a mail piece that names the country where mail is delivered.

SDC-0055-057-JE-8022

Precise and Unambiguous

Express exact meaning of the concept

Good - The calendar date when latitude and longitude coordinates were determined.

Poor -The data collection date.

SDC-0055-057-JE-8022

Concise

Comprehensive without extraneous terms

Good -The name of the person to contact for

clarification of technical information.

Poor -The individual whom EPA or State officials may

contact if clarification of the information reported on the form is required.

SDC-0055-057-JE-8022

Stand Alone

Stand alone without further definition

Good -

The Hydrologic Unit Code (HUC) that represents a geographic area that includes a surface drainage basin or a combination of drainage basins.

Poor -

The Hydrologic Unit Code (HUC) that represents a cataloging unit.

SDC-0055-057-JE-8022

Without Embedded Rationale

Does not include rationale, functional usage, or procedural information.

Good -The distance in meters above or below a reference surface.Poor -The distance above or below a reference surface, measured in meters rather than feet, because meter is an international standard.

SDC-0055-057-JE-8022

Avoid Circular Reasoning

A data element should not be defined in the context of another data element

Poor -

Facility Identification Number -- The number assigned to a facility.

Facility -- A site identified by a facility identification number.

SDC-0055-057-JE-8022

Consistent with Related Data

A common terminology and syntaxGood -

The code that represents the method used to determine vertical coordinates.

The name of the method used to determine vertical coordinates.Poor -

The code that represents the method used to determine horizontal coordinates.

The method used to determine the latitude and longitude of a place.

SDC-0055-057-JE-8022

EDR Definition Syntax

Use a phrase, not a sentenceThe name of the country where mail is delivered.

Begin the definition by stating the representation class, such as: The name of .. The code that represents…The text that describes … The measure of the …..The number assigned by….to identify…..The sum, dimension, capacity (quantity) of …..

SDC-0055-057-JE-8022

EDR Definitions in Context

Must state exactly the same concept

Same -The measure of elevation in meters, above

or below a reference datum. (Registry)The vertical distance in meters either above

or below a reference surface. (Standard)Different -

The height or depth of a facility relative to sea level.

Good definitions Good definitions promote the promote the

standardization and standardization and reuse of data reuse of data

elements, leading to elements, leading to data sharing and data sharing and

integration of integration of information systems.information systems.