Free-Text Searching; Controlled Vocabulary; Proximity Operators

IS530 Fall 2009 1 Dr. Dania Bilal

Viewing Search Results in Dialog Lecture Notes: 10/19/09

Web search engines and non Dialog databases, search results are displayed and can be printed using the Print option of the engine or database. In Dialog, viewing search results on the screen can be done by using DS to display the results or the Type command. Dialog has 9 defined formats for viewing and typing the results. These are described in Chapter 4 of the Lab Book. Dialog also allows users to specify their own format for typing and viewing the results. The common user-defined formats are ti, au, ab, and de. These are also covered in Chapter 4.

Demo#1. Viewing and typing results in Dialog.

Controlled Vocabulary; Free Text Searching; Proximity Operators Controlled vocabulary searching is based on subject terms (or descriptors) that are taken from a database thesaurus or from records containing terms in the descriptor field.

 A thesaurus contains broader terms (BT), narrower terms (NT), and related terms (RT). It indicates the terms that are allowed to use in searching (USE) and those that are not allowed (USED For). .  Indexing standards vary among databases. Not all databases have thesauri; instead, they have alphabetical listing of terms indexed in each database.  Controlled vocabulary may or may not be useful in searching.

Accessing the Dialog Online Thesaurus

If a Dialog database has a thesaurus, you may search it by using the Expand or e command (after using the Begin command in a specific database).

Example: e bias

Demo #2. Dialog Expand command.

Search Techniques Using Controlled Vocabulary in Dialog

 Bound Descriptors: Intact multi-word descriptors that are also known as phrases. o Example: vocal music/de  Suffix searching with descriptors: A descriptor can be searched within a specific field to narrow the retrieved results. This field is called a “tag” in Dialog. IS530 Fall 2009 2 Dr. Dania Bilal

Use of the suffix /df

 The suffix /df is used to limit search results to records containing a ONE- WORD DESCRIPTOR (also known as a FULL DESCRIPTOR).  Using of the /df field tag for a one-word descriptor is different from using the /de tag for the same descriptor.

Example: sleep/df will retrieve records assigned the descriptor sleep as one word. It will not retrieve records assigned the term sleep disorder or sleep apnea or other terms composed of more than one word. On the contrary, searching the term sleep/de will retrieve records assigned the descriptor sleep disorder, sleep apnea, sleep walking, and so forth in the descriptor field. Use of /df is more restrictive in terms of the number of records retrieved than use of /de

The suffix /maj is used to indicate a major descriptor .  Major descriptors used in Dialog are database-specific. Major descriptors in Dialog are indicated with the symbol * in the descriptor field.

Example: sleep/maj

Demo# 4. Dialog controlled vocabulary searching using /de, /df, /maj suffixes.

Searching Dialog with suffixes

 Field tags or suffixes are found in Dialog’s Bluesheets and they may vary by database. Suffixes are used to narrow search results. Use of suffixes are not limited to controlled vocabulary.

The most commonly used field tags for suffixes are:

/ab (for abstract) /ti (for title) /de (for descriptor) /df (for one word descriptor/full descriptor only) /id (for identifier) IS530 Fall 2009 3 Dr. Dania Bilal

Accessing the Online Thesaurus in Non-Dialog Databases

If a database has an online thesaurus, you will be able to access it by clicking on Thesaurus. Type the term you want to view and select from the displayed list of narrower or related terms.

Demo #5. Thesaurus structure in non Dialog databases.

Free Text (Keyword Searching)

Free text or keyword searching is typically used when:

 a database has no thesaurus;  a database has a thesaurus but the controlled vocabulary is inadequate;  a term is new and, therefore, has not been included in a database thesaurus;  a term is not new, but still excluded from a database thesaurus;  use of descriptors from a thesaurus does not yield satisfactory results;  a known item is being sought (e.g., specific book or journal title; specific title of an item); and  a database user does not want to take the time to select descriptors.

Problems with Free Text/Keyword Searching

 Free-text searching can yield more but imprecise results (i.e. high recall but low precision).  Free text searching can yield false drops. o Examples of false drops: . Reverse concepts . Concepts that use the same words but have different meanings . Acronyms that are irrelevant to the search

How to Avoid False Drops?

A. Use proximity operators. The most commonly used proximity operators are:

() These empty parentheses are the same as using the (w).

. Example: child()abuse  same as child(w)abuse IS530 Fall 2009 4 Dr. Dania Bilal

(W) means With. This operator is used to retrieve terms adjacent to each other in the order specified.

. Example: child(w)abuse

(nW) where n is the number of intervening words separating the terms.

. Example: information(1w)retrieval

(N) means Near. This operator is used to retrieve terms adjacent to each other but in any order.

. Example: Calcification(N)physiologic This will retrieve calcification physiologic or physiologic calcification and without loosing the meaning or context of the phrase.

(nN) where n is the number of words that should separate the terms.

. Example: test(3N)bias This search will retrieve items about either test bias or bias on taking a test.

(F) means same field. This operator retrieves two or more terms from the same field.

. Example: test(f)bias

(L) means same link in a descriptor (the descriptor and its linked subheading describing a specific aspect). This proximity operator is database specific and very useful in searching medical databases.

. Example: bone marrow(L)transplantation This search will retrieve the descriptor heading bone marrow and its subheading transplantation as they exist in the descriptor field of a record. The terms will be displayed as

Bone marrow----transplantation

(S) means same paragraph: This operator retrieves records where the terms appear in the same grammatical paragraph.

B. Use truncation carefully.

Demo#6. Use of proximity operators. IS530 Fall 2009 5 Dr. Dania Bilal

Ladder of Specificity of Operators and field tags

From the most restrictive to the least restrictive search results, note the level of specificity for these operators to apply in searching Dialog.

1. full descriptor in descriptor field /df 2. major descriptor in descriptor filed (as applicable) /maj 3. term from descriptor field /de 4. Linked descriptors in descriptor field (L) 5. (W) 6. (1W) 7. (2W), (3W), etc. 8. (N) 9. (1N) 10. (2N), (3N), etc. 11. (F) 12. (S) 13. Boolean AND (words appearing anywhere in a record)