Post and Pre Coordination
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Thomas Ivie Spring 2011 SLIS 5200 SWIM-A Concept Briefing Pre- and Post-Coordination Abstract This briefing defines pre and post-coordination, addresses their purpose and use, discusses the process for of them, and discusses their benefits and limitations. Pre- and post-coordination are indexing systems that assign descriptive words, terms, or phrases to intellectual content. Their purpose is to assist the user in finding the materials they desire. Pre- and post-coordination employs a four stage process of content analysis, concept selection, concept translation, and term combination. Pre-coordinate benefits include better precision and recall. Post-coordination benefits include the elimination of the need to learn rules, subject headings, and ordering; users can form their own query based on their information needs; and it empowers the user by allowing them to mix and match terms without worry of order. Pre-coordination limitations include complexity, use of incorrect terms, and out-of context results. Post-coordination limitations include diminished precision, high recall, and information overload. Examples are given to demonstrate how pre- and post-coordination affects user searches by way of subject access, ordering, partial matches, and controlled vocabulary.
Transcript of Post and Pre Coordination
Thomas IvieSpring 2011
SLIS 5200 SWIM-AConcept Briefing
Pre- and Post-Coordination
Abstract
This briefing defines pre and post-coordination, addresses their purpose and use, discusses the processfor of them, and discusses their benefits and limitations. Pre- and post-coordination are indexing systemsthat assign descriptive words, terms, or phrases to intellectual content. Their purpose is to assist the user in finding the materials they desire. Pre- and post-coordination employs a four stage process of contentanalysis, concept selection, concept translation, and term combination. Pre-coordinate benefits includebetter precision and recall. Post-coordination benefits include the elimination of the need to learn rules,subject headings, and ordering; users can form their own query based on their information needs; and itempowers the user by allowing them to mix and match terms without worry of order. Pre-coordinationlimitations include complexity, use of incorrect terms, and out-of context results. Post-coordinationlimitations include diminished precision, high recall, and information overload. Examples are given todemonstrate how pre- and post-coordination affects user searches by way of subject access, ordering,partial matches, and controlled vocabulary.
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Introduction
This briefing defines pre and post-coordination, addresses their purpose and use, discusses the processfor them, and discusses their benefits and limitations. It also provides examples to demonstrate how pre-and post-coordination affects user searches.
Definition
Pre- and post-coordination are indexing systems that assign descriptive words, terms, or phrases tointellectual content (Jacob, 2004, p. 534; Rowley, 1992, p. 280; Zeng, 2006, p. 53). Pre-coordination of terms occurs before searching takes place and is facilitated by an indexer (Rowley, 1992, p. 280). Post-coordination of terms is facilitated by an indexer but occurs during the search portion of the retrievalprocess by the searcher (Rowley, 1992, p. 282).
Purpose and implications
Purpose and use of pre- and post-coordination
The purpose of pre- and post-coordination is to assist the user in finding the materials they desire. Pre-coordinate systems originated with paper catalogs and printed indexes (Rowley, 1992; Knight, 2009).Pre-coordination provides search strings and cross references to show semantic relationships through acontrolled vocabulary (Knight, 2009). Order of the terms is integral to the process of retrieval andmaintains the consistency in treatment of terms (Bodoff & Kambil, 1998). Post-coordinate systems areknown for use in computerized searches (Bodoff & Kambil, 1998). Post-coordination was designed torectify problems associated with pre-coordination, uses natural language or controlled vocabulary termsand is a grouping instead of a system of organization (Jacob, 2004; Knight, 2009).
Process for pre- and post-coordination
Pre- and post-coordination employs a four stage process. Content analysis involves what the informationsource is about. Concept selection involves formation of policy that determines how exhaustive theindexing will be. Concept translation involves natural language or controlled vocabulary terms to be in theindex. Term combination involves ordering of terms and is dependent on the indexing system (Knight,2009, pp. 12-13).
Benefits and limitations of pre- and post coordination
Benefits
Pre-coordination provides better precision because it can use different syntaxes from various ideas butusing identical terms to produce good results (Bodoff & Kambil, 1998; Jacob, 2004). It is enhanced byintelligent term orderings performed by a cataloger, allows reasonable groupings, and lowers partialmatches (Bodoff & Kambil, 1998). Recall is enhanced by the ordering of terms (Bodoff & Kambil, 1998).
Post-coordination eliminates the need for users to learn rules, subject headings, and ordering. It is lessexpensive and faster and includes interactive communication between the searcher and system becausethe searcher can form their own query based on their specific information need (Bodoff & Kambil, 1998;Jacob, 2004; Knight, 2009). It empowers the user by allowing them to mix and match terms without worryof order and can provide higher recall (Bodoff & Kambil, 1998; Jacob, 2004; Knight, 2009).
Limitations
Pre-coordination puts a strain on communication between the user and system because it is complicatedby available subject headings, their rules, and ordering that predetermine the make-up of the sets of retrievable data (Bodoff & Kambil, 1998; Jacob, 2004; Knight, 2009). Precision is potentially limited
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without a thesaurus in hand, causing the searcher to guess terms (Bodoff & Kambil, 1998). Improper intelligent term orderings can cause users to browse irrelevant hits because of out-of-context results(Bodoff & Kambil, 1998). It is expensive and very slow to index in controlled vocabulary (Knight, 2009).
Lack of order among search terms diminishes precision in post-coordination (Bodoff & Kambil, 1998). Itresults in a high recall because multiple search terms are independent. This leads to more out-of-contextresults, information overload, and causing the user to not notice any more than the first few hits (Bodoff &Kambil, 1998; Knight, 2009).
Examples
Example #1: Subject access: pre- and post-coordination
Pre-coordination: Construction Industry – ItalyOnly allows fixed order of each subject to find relevant information that results in higher precision andlower recall.
Post-coordination: Italy Industry Construction Allows a query to have terms in any order, results in lower precision and higher recall, and can lead toout-of-context results and information overload.
Example #2: Ordering to avoid partial matches in pre-coordination
A book on photography studios and dark rooms has an LCSH of Photography –studios and darkrooms. If the book were cataloged under Photography Studios –dark rooms, then the searcher who isinterested in photography dark rooms and looked under „Photography Studios‟ would find a partial matchand have to browse many more items than if they searched a correct LCSH in correct citation order.Correct citation order increases precision, lowers recall, and reduces information overload.
Example #3: Post-coordination search and improper partial matches
A post-coordinated search for a photography book using the terms „dark rooms, photography‟ results inlow precision and large recall of items that have an improper partial match. It would produce a list of books that includes dark rooms in any context (probably a lot of fiction) and any books aboutphotography, many of them will not match what the searcher wants and leads to information overload.
Example #4: Controlled Vocabulary to increase precision in post-coordination
A post-coordinated search for „Cars‟ results in low precision and high recall. The use of a controlledvocabulary that includes a descriptor like „Volkswagen‟ increases the precision and lowers the recallbecause it limits „Cars‟ to Volkswagens. The descriptor of „diesel‟ would further limit Volkswagens to thosewith diesel engines, increasing precision and lowering the recall further.
Conclusion
Pre- and post-coordination are indexing systems that assign descriptive words, terms, or phrases tointellectual content (Jacob, 2004; Rowley, 1992; Zeng, 2006). The purpose of both indexing systems is toassist the user in finding the materials they desire. Pre- and post-coordination employ a four stageprocess (Knight, 2009) providing post-process systems that have inherent benefits and limitations, sharedand independent (Bodoff & Kambil, 1998; Jacob, 2004; Knight, 2009). The examples demonstrate howpre- and post-coordination affects user searches by way of subject access, ordering, partial matches, andcontrolled vocabulary. As Thomas Mann (2003, p. 54) pointed out, “Neither I nor anyone else is arguingfor precoordination rather than postcoordination. We need both.”
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References
Bodoff, D. and Kambil, A. (1998). Partial coordination. I. The best of pre-coordination and post-coordination. Journal of the American Society for Information Science, 49(14), 1254-1269.Retrieved from http://onlinelibrary.wiley.com/doi/10.1002/%28SICI%291097-4571%281998%2949:14%3C1254::AID-ASI4%3E3.0.CO;2-O/pdf
Jacob, E. (2004). Classification and categorization: A difference that makes a difference. Library Trends,52(3), 515-540. Retrieved fromhttp://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.125.255&rep=rep1&type=pdf
Knight, J. (2009). Pre- and post-coordinate indexing: Strengths and weaknesses. Catalog & Index ,no.158, p. 12-16.
Mann, T. (2003). Why LC subject headings are more important than ever. American Libraries, 34(9), 52-54. Retrieved from http://connect.ala.org/files/15532/mannarticle_pdf_49df66dad1.pdf
Rowley, J. (1992). Organizing knowledge, 2nd
ed. England: Gower Publishing.
Zeng, M. (2006). Sharing and use of subject authority data. International Cataloging & Bibliographic Control , 35(3), 52-54.
