Nursing classification schema have been developed at varying levels of abstraction and offered as ways to organize and categorize nursing phenomena, such as the North American Nursing Diagnosis Association (NANDA) Nursing Diagnosis Taxonomy (Warren & Hoskins, 1995), the Omaha System (Martin & Scheet, 1995), the Nursing Interventions Classification (NIC) (Bulechek, McCloskey, & Donahue, 1995), and the Nursing Outcomes Classification (NOC) (Johnson & Maas, 1995). However, at a more basic level, the question arises, why does the discipline of nursing need a taxonomy or taxonomies?

Table 1.
Relevant Terms and Definitions
Term	Definition
Classification	A systematic arrangement of classes; a structural framework arranged according to similar groups (Lang, et al, 1995).
Database	A collection of interrelated files with records organized and stored together in a computer system (Lang, et al, 1995).
Language	A set of characters, conventions, and rules used to convey ideas and information (Lang, et al, 1995).
Taxonomy	Method of classifying a vocabulary of terms for a specific topic according to specific laws or principles (Lang, et al, 1995).
Terminology	Words and/or phrases used to describe a concept or phenomenon
Unified	Linked, affiliated, associated to make into a unit or coherent whole (McCormick, 1988a)
Uniform	Having the same or similar form with others; constant (McCormick, 1988a)
Vocabulary (Nomenclature)	The stock or repertoire of words from which to name or describe phenomena within a language or knowledge base (Lang, et al, 1995)

Several reasons can be identified to explain this need. First, employers, insurers, providers, payers, and policy-makers require objective, science-based information to make critical decisions about meeting health care demands, supplying health care services in the marketplace, providing access to services, allocating resources, and determining the costs and quality of care. Second, market forces, or competition, necessitates accountability, and documentation is required to substantiate accountability for processes and outcomes of care. Data on outcomes related to quality and costs will provide information to the public, and ultimately enable consumers and payers to determine health care-related value, and make tradeoffs in level of quality desired for a given cost. Finally, data are a requisite for conducting empirical research; hence, researchers need data to answer research questions related to practice, identify "best" practices, develop and test models of care, design decision-support models, and determine efficient and effective utilization of resources. While no one data source will meet all of these needs, a common vocabulary will enable linkages among data sources to be made.

A discussion of "taxonomy" of any kind naturally polarizes individuals and groups on a philosophical level, given that individuals and groups conceptualize and classify phenomena in different ways. In fact, the question of whether nursing needs one or more taxonomies or many conjures up thoughts of similar disciplinary debates about nursing theory and research methodology: does the discipline need one or many? Each side of the debate has certain advantages and disadvantages, and in some cases, a disadvantage of one side becomes the advantage of the other. The major advantage of advocating one taxonomy is simplicity - if there is one taxonomy, then there is the assumption that everyone is or will be made aware of it, understands the vocabulary and classifications, accepts it, and utilizes the known taxonomy. The existence of one taxonomy eliminates confusion over terminology and meaning, and necessitates disciplinary agreement about the vocabulary and classifications. For example, most nations use the International Classification of Diseases Version 9 or 10 (ICD-10) to describe country-level mortality and health care costs, which, in turn, facilitates the comparison of medical conditions across countries.

However, the opposing argument in a discussion of taxonomy is readily apparent in a national health care environment that supports many types of health care delivery, and that implies multiple service options, open discourses about those options, and the freedom to choose amongst options. For example, Henry (1997) emphasizes that existing nursing classification systems recognized by the American Nurses Association (e.g., NANDA, NIC, NOC) are not sufficient to reflect the entire scope of nursing practice. Additionally, the argument for one taxonomy assumes that one taxonomy would be learned, interpreted, and operationalized in a similar fashion across all individuals who practice nursing. This assumption is clearly not reasonable. For these reasons and others, nurse scholars have debated and opposed the advocacy of one taxonomy for nursing.