A classification system can be as simple as an alphabetical listing or as formal as a numerical taxonomy. The ideal classifications of mathematics and logic with mutually exclusive categories are seldom found in other disciplines (Bailey, 1994). Biology struggles to distinguish between the animate and inanimate and medicine finds obesity in its classification of diseases (Webster, 1984). Classification is not a simple task with the complexity of nursing, phenomena of concern.

How did the current North American classification system grow? It was nurtured through the efforts of NANDA Taxonomy Committee chairpersons, Drs. Phyllis Kritek, Joyce Fitzpatrick, and currently Kay Avant. Models and frameworks (Maslow, Abdellah) for organizing nursing diagnoses were suggested by participants at the First National Conference and later (Lunney, 1984; Loomis, 1987) but from 1973 to 1986 diagnoses were arranged in an alphabetical listing. In retrospect this was a wise decision for that time period. NANDA currently classifies nursing diagnoses into Taxonomy I, Revised using the structure of Human Response Patterns, as seen in Table 2. This structure for a classification system was accepted by participants in 1986 at the Seventh Conference.

TABLE 2.
HUMAN RESPONSE PATTERNS	DEFINITIONS OF HUMAN RESPONSE PATTERNS
CHOOSING.	To select between alternatives; the action of selecting or exercising preference in regard to a matter in which one is a free agent; to determine in favor of a course; to decide in accordance with inclinations.
COMMUNICATING.	To converse; to impart, confer, or transmit thoughts, feelings, or information, internally or externally, verbally or non-verbally.
EXCHANGING.	To give, replenish, or lose something while receiving something in return; the substitution of one element for another; the reciprocal act of giving and receiving.
FEELING.	To experience consciousness, sensation, apprehension, or sense: to be consciously or emotionally affected by a fact, event, or state.
KNOWING.	To recognize or acknowledge a thing or a person; to be familiar with by experience or through information or report; to be cognizant of something through observation, inquiry, or information; to be conversant with a body of facts, principles, or methods of action; to understand.
MOVING.	To change the place or position of a body or any member of a body; to put and/or keep in motion; to provoke an excretion or discharge; the urge to action or to do something; to take action.
PERCEIVING.	To apprehend with the mind; to become aware of by the senses; to apprehend what is not open or present to observation; to take in fully or adequately.
RELATING.	To connect; to establish a link between; to stand in some association to another thing, person, or place; to be born or thrust in between things.
VALUING.	To be concerned about; to care; the worth or worthiness; the relative status of a thing, or the esteem in which it is held; according to its real or supposed worth, usefulness, or importance; one's opinion of linking for a real person or thing; to equate in importance.
From: Fitzpatrick, J. J. (1991) Taxonomy II: Definitions and development — Table I: Definitions of human response. Classification of nursing diagnoses: Proceedings of the ninth conference, p. 25. Reprinted with permission, Nursecom,Inc.

Taxonomy is a term used interchangeably with classification system, such as in biology and other disciplines. Yet it is actually defmed as the study of classification including its bases, principles, procedures and rules (Sneath & Sokal, 1973, p.3). Similar to the term, classification system, taxonomy can refer to both the process of classification and the end product. In the NANDA taxonomy, the roots of the term "human response" lie in the ANA Social Policy Statement (Kritek, 1989). In this document nursing is defmed as the diagnosis and treatment of human responses to actual or potential health problems. (The term "problems" is used in a very broad, generic sense, such as that which is of therapeutic concern to the nurse, the patient, or both.) Human responses are the indicators of patterns (actual or potential health problems).

Between 1977 and 1982 a group of 14 prominent nurse-theorists developed an organizing framework from which the patterns in Table 2 are taken (Roy, 1982a, 1982b). Sister Callista Roy, a member of the National Task Force that preceded NANDA, coordinated the work of this group at national conferences and by mail. It was the first time that these leaders in nursing theory

1. had met together,
2. worked with a group of clinical specialists to test their work, and
3. developed a common conceptual framework for nursing and for organizing nursing diagnoses.

Kerr (1991) outlined methods for taxonomy validation but the literature does not reflect the use of these methods in validating the NANDA Taxonomy or further developing the pattern-definitions in Table 2. Clinicians have attempted to use the patterns as an assessment tool or in information systems and, on this basis, many have rejected their abstract nature. In 1998, the Taxonomy Committee under the leadership of Dr. Kay Avant explored other typologies for organizing diagnoses that may be more useful (North American Nursing Diagnosis Association, In Press). A second factor for re-examining the nine key concepts was the difficulty classifying diagnoses that crossed patterns, such as syndromes (Avant, 1997; McCourt, 1991.). Comments and suggestions will be elicited from the profession prior to the Taxonomy Committee's report to the Fourteenth NANDA Conference in 2000. Similar to diagnosis review, taxonomy review is based on the philosophy that all nurses should have an opportunity to participate in the development of a classification system for the profession.