Frequently Asked Questions about the USGS Thesaurus and catalog

Terms represent concepts, but it is the concepts themselves and their relationships, not the terms, that constitute the thesaurus.

Terms are related to one another in three different ways:

Hierarchy

A term always has an "is a" relationship with its broader term (BT); a narrower term (NT) can always be said to be "a type of", "a part of", or "an instance of" the parent term.

Preference

For a given concept, one term is chosen as the preferred term or label, and is referred to as the descriptor. Other terms that refer to the same concept are referred to as lead-in terms or non-preferred terms. A non-preferred term is not necessarily a synonym of the preferred term.

Generic relationships

Where concepts are related in some way that cannot be expressed as an "is a" sentence, the thesaurus simply connects one term to another without specifying the nature of the relationship. This is different from more elaborate knowledge-management systems such as topic maps or ontologies in which such generic relationships are always identified and categorized.

Thesaurus interfaces such as Science Topics are not intended to replace traditional search or browse interfaces. In concert with the new "USGS by State" and "About USGS" sites, they supplement existing navigational aids to USGS web information.

1. The USGS Thesaurus is designed to conform with a recognized standard, ANSI/NISO Z39.19. This standard has been in widespread use throughout the information science community for many years.
2. The thesaurus is broad and shallow. It is not intended to enumerate or distinguish the fine details of USGS science, and it is not intended to duplicate detailed search within a scientific database on a particular topic that would ordinarily be provided by a web site developer.
3. The thesaurus is explicitly intended for use in a web browsing environment. Consequently it is strictly hierarchical. No term has more than one broader term; alternative broader terms are shown as related terms instead. Also the number of top terms is intentionally kept small to enable browse interfaces to function well.
4. The thesaurus is monolingual. Foreign-language equivalents are possible in principle but have not been incorporated into the current design.
5. The thesaurus is intended to cover only those facets of information for which other controlled vocabularies were either not available or were not optimal for categorizing USGS information. Consequently the thesaurus does not include place names, types of named geographic features, detailed biological taxonomy, chemical and mineral names, USGS publication series names, or names of organizational units and programs.

Development methods

Specialists recognize two different strategies for building controlled vocabularies: top-down, in which terms and their relationships are defined intuitively prior to their direct application in an indexing situation; and bottom-up, in which terms and relationships are added to the vocabulary in the process of indexing. But the same specialists also recognize that most vocabularies are developed using a combination of these two abstract approaches. We developed the USGS thesaurus using this combined strategy. Beginning by simply listing lots of important terms, we grouped those terms using a card-sorting procedure, and then refined the hierarchy with intuitive processes (that is, by relying on what we know). Subsequent revisions have occurred by group deliberation.

Preliminary development of the thesaurus was conducted using commercial software (MultiTES) by a contractor. Subsequent development and revision has occurred in a web-based database application developed by the group meeting the specific needs of this project.

Review of existing controlled vocabularies

We examined many similar controlled vocabularies of various types before and during this process. Examples are the GEOREF thesaurus produced by the American Geological Institute, the CERES thesaurus ( http://ceres.ca.gov/thesaurus/) the Geographic Names Information System (GNIS), the Integrated Taxonomic Information System (ITIS), the categorization scheme used in the Marine Realms Information Bank (http://mrib.usgs.gov/), and numerous smaller or more specialized vocabularies such as glossaries of scientific and technical terms presented on USGS web sites.

1. They would imply an isolation of scientific focus that does not accurately reflect the cross-disciplinary work of our researchers.
2. They mean different things to people inside and outside USGS.
3. They change. Every year, some programs change names, combine with others, drop out, reappear, or change in scope or focus.
4. They reflect political and organizational concerns of USGS, DoI, the executive and legislative branches of the government, and sometimes of state and local governments, rather than the concerns of scientists or citizens outside of the political process and organizational politics.
5. USGS has developed a specialized interface (About USGS) to explain how the Bureau is organized and how it carries out its work as an agency of the government.

We do not deny that the names of funded programs and organizational units are important. We assert instead that this sort of information answers different questions than the ones to which our work is directed. Descriptions of our organization and programs answer the question "How does USGS describe its own organization now and how does it logically group its research and monitoring work now?"

We view these issues from a longer-term perspective. Programs and organizations within USGS have changed and will continue to change through time. What matters in describing the results of our scientific research and monitoring activities is what we studied, how we studied it, and what we found.

But it is possible to describe USGS organizational structures using a formal thesaurus (here is an example) and this can be seen as one way to categorize some of our information, in particular organizational web sites and pages that describe specific funded program activities. We assert that this is not the only way to categorize USGS science, and that a bureaucratic view is especially unsuitable for use by people outside the government.

When you find a concept that does not seem to be represented in the thesaurus or a variant of phrasing or punctuation that you feel is common enough to be a lead-in term, please contact the thesaurus working group of the Enterprise Web project. You can contact the thesaurus editorial group, GS_Thesaurus@usgs.gov.

Note that some words or phrases may appear in the thesaurus as "lead-in" terms, meaning terms that a user might enter to find an appropriate descriptor. Lead-in terms will generally refer to the same concept as the descriptor, and may be synonyms. However in some cases a lead-in term is a more specific concept that hasn't been designated a separate category. These lead-in terms are sometimes referred to as "non-preferred" terms in the literature of the library community.

Alphabetical listings of the thesauri are generated dynamically:

• USGS Thesaurus
• Common geographic areas
• Alexandria Digital Library Feature Type Thesaurus
• U.S. National Parks
• Wildlife Refuges
• Lithologic classification of geologic map units

ITIS is maintained separately by the USDA.

The wording of the question indicates there might be a misunderstanding lurking beneath, so I want to clarify one point first. The thesaurus is not really intended to improve the action of external search engines. The USGS search engine might be tuned to look at keywords in HTML pages (the <meta> tags in the HTML header), but its function will probably continue to be focused on providing full-text search. [USGS guidelines for use of keywords in HTML metadata are currently undergoing revision.] Index terms can indeed be put into web pages, and that may be helpful, but it is not the primary focus of our work to detect those index terms and act on them. Instead, we believe the power of the thesaurus can only be exploited by web interfaces designed specifically to work with index terms and catalog records.

That said, some general guidance can be offered. First and foremost is to specify page titles well. Use clear terms and do not assume that every reader knows the scope within which your page appears. Include county and state in the title if your page is about something in a specific county or state.

Second, consider using preferred terms from the thesaurus if they fit your meaning. Use of terms that are designated as descriptors or lead-in terms in the thesaurus will make it more likely that a search of the USGS web will connect what you have written with what other people have written about the same subject. This applies primarily to headings on the page and the <title> element of the HTML header.

Third, if you manage a glossary or other online vocabulary, consider which terms in your vocabulary link to thesaurus terms and how they relate. Link where it is practical, clarify where your usage is different, and engage the thesaurus working group in conversation about terms on whose meaning or usage we appear to disagree.