View
220
Download
2
Category
Tags:
Preview:
Citation preview
LIS618 lecture 4
Thomas Krichel
2003-02-19
Structure of talk
• Before online searching • Introduction to online searching• Introduction to DIALOG
– Overview– bluesheets
before a search I
• what is purpose– brief overview– comprehensive search
• What perspective on the topic– scholarly– technical– business– popular
before search II
• What type of information– Fulltext– Bibliographic– Directory– Numeric
• Are there any known sources?– Authors– Journals– Papers– Conferences
before search III
• What are the language restrictions?
• What, if any, are the cost restrictions?
• How current need the data to be?
• How much of each record is required?
DIALOG
Literature
http://training.dialog.com/sem_info/courses/pdf_sem/dlg1.pdf
http://training.dialog.com/sem_info/courses/pdf_sem/dlg2.pdf
http://training.dialog.com/sem_info/courses/pdf_sem/dlg3.pdf
http://training.dialog.com/sem_info/courses/pdf_sem/dlg4.pdf
Dialog is a databank
• over 500 databases• these are also known as files and cover
– references and abstracts for published literature,
– business information and financial data;– complete text of articles and news stories;– statistical tables– Directories
• DIALOG uses the Boolean model
DIALOG interface
• is still rooted in "traditional" database systems
• dismissed as "dial-a-dog"
• is uses a command-driven interface
• it is very complicated to learn fully
• it is not suitable for the end-user
• it therefore offers a valuable skill to the information professional
• it is a challenge for a professor to teach
Accessing DIALOG
• On the web, go to
• http://www.dialogweb.com/
• Enter username and password, then click on logon
• When it is all done, click logoff in the top menu.
two steps in DIALOG
• step one: select databases (aka files) to look at
• step two: perform searches on the selected databases
• You may wonder why one does not have one single step like in a search engine. Discuss.
• today we concentrate on the second step
working on selected files
• We assume that we have selected database that we know and we look at the search interface on the selected database.
• The database selection process is a bit more complicated, covered next week.
• First, let us login and look at the command prompt.
• Then we select the first database (file) with the begin command
The begin command
• As its name suggests, usually the first command.
• begin number, number,…
• selects files with numbers number
• Once they are selected they can be searched.
• Now select the ERIC "begin 1"
• "Begin 1" can be abbreviated as "b 1"
Substeps in the second step
• Identify search terms
• Use Dialog basic commands to conduct a search
• View records online or print the results
the 's' (select) command
• Once issued the "begin" command to select a database, we issue the "s" command on the database.
• "s query_terms" where query_terms are the query terms
• This will search the index of selected database in full-text view for the query issued
• It will not find any of the following: "an and by for from of the to with". They are stop words.
connectors
• If you want to use several keywords there are three ways– you can truncate search terms – you can build an expression by putting
several keywords together. This is achieved by DIALOG's connectors.
– you can combine several expressions with the use of Boolean operators
• we will cover this is in turn now
truncation of terms
• Open Truncation– "select path?" retrieves all words that begin
with path: paths, pathos, pathway, pathology
• Controlled-Length Truncation– "select path? ?" retrieves the root and up to
one additional character: paths– "select path??" retrieves the root and up to
two additional characters: paths, pathos
truncation of terms II• Embedded Character truncation can be used
for variant spellings:– "select organi?ation" -> organization
organisation – "select fib??board" -> fiberboard fibreboard
• This truncation feature is also useful for searching for unusual plural forms:– "select wom?n" -> woman women
• You can also do prefixes by putting the ? in the beginning. – "?mobile" -> automobile metamobile
Use of connectors
• Connectors are used to put several words together.
• One instance where this is useful is when you have words that on their own mean different things.
• For example "mate" is a herbal beverage consumed in South America. Looking for mate on the Internet retrieves a lot of singles' pages.
terms connected to mate
• What other terms to be used? – matear (suck mate)– matero (mate sucker)– cebar (prepare mate)– cebador (mate preparer) – yerba (mate herb)– bombilla (mate straw)
connectors I
• '(W)' requires terms to appear one after the other next to each other e.g. 'yerba(W)mate?' matches "yerba mate".
• '(i W)' where i is an integer, means followed by at most i words, e.g. 'ceba?(3W)mate?' matches "cebar un maravilloso mate" but not "cebador guapo mirando un buen mate"
connectors II
• '(N)' requires terms to be next to each other e.g. 'yerba(N)mate?' matches "yerba mate" or "mate yerba".
• '(i N)' where i is an integer, means proximity by at most i words, e.g. 'ceba?(3N)mate?' matches "cebar mate" or "matear con la cebadora".
• '(S)' searches for the occurrence of connected terms in the same paragraph.
using Boolean operators
• In your query, you can combine several expressions with Boolean operators
• Example: "?SELECT LIBRARY(W)SCHOOL? AND DISTANCE(W)EDUCATION"
• But I usually do not issue such fancy queries.
executing several searches
• there can be several searches done sequentially, and the results sets are saved by the system.
• Each time the system assigns a set number.
• These can be combined in Boolean expressions, e.g. 's S1 or S2 and S3'
• Remember that Boolean operations are set-theoretic!
Boolean operators
• when using Booleans, be aware that "and" has higher precedence than "or".
• Thus:a or b and c
is not the same as
(a or b) and c
but it is
a or (b and c)
type command
type set/format/range
• set is a result set
• format is a format
• range can be – start – end
• start is a record number to start• end is a record number to end
– all
formats are defined
• 2 -- full record except abstract• 3 or medium – citation• 5 or long – full except full text• 6 or free – title and dialog number• 8 or short – title plus indexing terms
– useful to find other indexing terms
• 9 or full – everything• KWIC or K – keywords in context
http://openlib.org/home/krichel
Thank you for your attention!
Recommended