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What is the Relationship Between BT and NT?  Normally, BT and NT are "inverse" links. In other words, if X is a broader term to Y, then Y is a narrower term to X, and vice versa. For example, if a thesaurus contains the entryBTNT PENS BT WRITING MATERIALS you would expect it also to have the entry WRITING MATERIALS NT PENS HMD2SPI376 - Slide 6

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How Many BT References Can a Term Have?  A thesaurus is usually "polyhierarchical"; this means that a term can have more than one immediately broader term and more than one BT reference. For example, SOCIAL PSYCHOLOGY BT PSYCHOLOGY BT SOCIOLOGY Polyhierarchy avoids futile arguments about the "best" broader term to choose. HMD4SPI376 - Slide 6

...  Some terms in a thesaurus have no broader terms and so no BT references. Such terms are usually fairly broad in meaning, at least within the subject area covered by the thesaurus. For example, in a sports thesaurus, "SPORTS" might have no broader terms. HMD5SPI376 - Slide 6

When Should BT/NT References Be Omitted?  You should not indicate every hierarchical relation explicitly in your thesaurus. That could make the entries too long and difficult to read. Instead, omit those links that are implied by other links. HMD6SPI376 - Slide 6

...  Suppose X is a broader term to Y, which in turn is a broader term to Z. Do not make BT/NT references between X and Z. HMD7SPI376 - Slide 6

...  For example, PLANT PRODUCTS NT FRUIT and FRUIT NT FRESH FRUIT but not PLANT PRODUCTS NT FRESH FRUIT HMD8SPI376 - Slide 6

When To Use an RT Reference  An RT reference is used for non- hierarchical semantic relations in a thesaurus. To decide whether there should be an RT reference between two preferred terms X and Y that do not have a hierarchical relation, you can use the following test:RTsemantic relation Should an indexer or a searcher considering using X be reminded of the existence of Y? HMD9SPI376 - Slide 6

What Is the Relationship between RT and RT?  Normally, RT is its own "inverse" link type. In other words, if X has an RT reference to Y, then Y should have an RT reference to X. For example, if a thesaurus contains the entry PENS RT CALLIGRAPHY you would expect it also to have the entry CALLIGRAPHY RT PENS HMD10SPI376 - Slide 6

Semantic Categories of RT References  In constructing your thesaurus, you may find it useful to list some categories of semantic relations that you think should be covered by RT references. Here are some categories sometimes used, with examples. HMD11SPI376 - Slide 6

CategoriesExamples Time LEISURE READING RT LEISURE TIME Place FOREIGN LANGUAGES RT LANGUAGE LABORATORIES Product STILL CAMERAS RT PHOTOGRAPHS SHIPBUILDING RT SHIPS Cause VANDALISM RT HOSTILITY Agent COACHING RT COACHES Device PAINTING RT PAINT BRUSHES Application COMPUTERS RT WORD PROCESSING Part VEHICLES RT WHEELS Complement PARENTS RT CHILDREN HMD12SPI376 - Slide 6

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Taxonomy illustrated HMDSPI376 - Slide 615

Thesauri illustated HMDSPI376 - Slide 616

Faceted classification illustrated HMDSPI376 - Slide 617

Ontology illustrated HMDSPI376 - Slide 618