1. Searching the research literature
The Pearl Harvesting Information Retrieval Theory
Searching the research literature

2. Outline Developing a comprehensive search
Developing a comprehensive search filter
Internal validation of the search filter by using the Boolean Subtraction Procedure
Developing precision into the search
External validation of a search filter
Choosing databases to search
The Pearl Harvesting Search Thesaurus

3. Database search terms, filters and fields
A search term (also called a keyword) is a set of characters (i.e., a word or phrase) which represents a topic and therefore can be used to retrieve articles on that topic
A search filter is a set of search terms, all of which refer to the same topic
There are usually a number of search terms which all represent the same topic.
The database search engine looks for any occurrence of the letters and characters that are in the terms of the filter.

4. Search element hierarchy
4. Layers of different search filters
(is a search strategy)
3. Collections of search terms which all pertain to the same topic
(is a search filter)
2. Words or phrases
(are search terms)
1. Text and symbol Characters

5. Indexed fields
Articles are coded by subject heading, author, abstract, title, date, journal title, etc.
Subject headings are terms that are predefined as ones that are capable of retrieving citations on a topic
These predefined terms are located in a database thesaurus

6. Increasing Comprehensiveness
One important goal of searching the research literature is to find as many relevant citations as possible
There are many purposes to being comprehensive, for example
Systematic reviews
Student theses
Coursework or text development

7. Increasing Comprehensiveness
One easy way to gather more citations is to use the truncation function *
Any letters following a root word will be recognized by the search engine
For example if you just enter the search term teacher, that is likely that the search engine will retrieve; no more no less
It will miss citations with the plural teachers
But if you enter teacher* it will retrieve both

8. Increasing Comprehensiveness
There are usually many terms that can be used to represent the same topic
Entering many unique and relevant topic related search terms will increase the number of topic related citations that are retrieved

9. Expanding the number of search terms
Searching is an act of communication between the information seeker and the authors of articles in a field. Database indexers are also part of this conversation in that they provide subject headings to help people locate information

10. Expanding the number of search terms
there are many terms to denote the same topic
If the different terms used can be found then they can be harvested to be used in search filters.
the largest collection of terms that provide unique and relevant citations comprise a search filter that is maximally comprehensive for a specific topic

11. How to Locate Search Terms
Potentially relevant search terms can be found where there are conversations about the topic
Therefore texts with conversations about the topic can be analyzed to potential terms
Since it will be unmanageable to review all relevant texts, a purposive sampling of texts rich in the conversations can be used
It is important to sample a wide variety of sources in order to identify the range of terms used to denote a topic

12. Possible sources of text rich in th use of language of the topic under investigation
Relevant systematic reviews and meta-analyses (see the Pearl Harvesting Search Thesaurus for search filters on systematic reviews)
the search terms used in the reviews are one source where potential terms might be found
The language found in the title and abstract's of the original source references are another source to review

13. Possible sources of text rich in th use of language of the topic under investigation
Edited text books
Chapters in edited text books that relate to the use of terminology used to describe a topic can be reviewed
The chapter itself and the references of the chapter are two sources of information

14. Possible sources of text rich in th use of language of the topic under investigation
Crowd sourcing; a form of sampling
Gather a group of individuals who are familiar with a topic
Have individuals each enter keywords they know about the topic into a database
No restrictions are place so that the sampling is down independently and therefore randomly
Review relevant articles to locate potential search terms
Gather the potential terms and develop one llist of potential search terms

15. Rendering the potential terms for searching
Truncation ensures the variants of a term are accounted for
Double quotations ensures precision

16. Double quotations
Searching with phrases is prone to a problem of word adjacency
E.g., special education -> special programs in higher education
Easy solution is to use double parentheses “”
“special education” and only words side by side will be retrieved
Also helpful with names in Google, retrieves only exact spelling

17. Internal Validation of search terms
How to determine which terms are essential to the search filter
Boolean Subtraction Procedure

18. Boolean Subtraction Procedure
The purpose of this procedure is to determine whether a search contributes to finding citations on a topic that no other search term will find
If a search term fills this requirement it is deemed essential to the search filter

19. Boolean Subtraction Procedure
Method:
Potential search term A
NOT (all other potential search terms, e.g. B OR C OR D OR etc)
Review the results
See if any citations exist ; if not the term is not necessary
If citations exist check to see if any are relevant
If unique and relevant then that term is necessary

20. The Pearl Harvesting Search Filter
Combine all validated search terms using the Boolean OR function
A OR B OR C OR D OR etc.
Copy and paste the filter into the search engine

21. Using The Pearl Harvesting Search Filter
Most search engines have various fields that can used to search, e.g., title, abstract, author, journal title
There are also multiple field operators which allow for searching across multiple fields all at once
The most powerful operator is one that searches all of the fields
In the Proquest databases this is the default “everywhere”
In MEDLINE it is all fields, or .af
Often it is not recommended to use all fields however if the search filter has been developed to be precise then extra information will be gathered with minimal loss to precision

22. Developing Precision in the Search Filter
1. phrases entered with double quotations tells the search engine to only retrieve citations that contain the words in the phrase in the specific order specified
Failure to use double quotes may result in the search engine looking for the words separately anywhere in the bibliographic information, i.e., that is very imprecise

23. Developing Precision in the Search Filter
2. Word sense disambiguation
Some words have numerous more specific versions and therefore can be further specified to achieve better precision
These are referred to as polysemic terms
For example, review is very general including such meanings as “book review”
Therefore it can be further developed to be “systematic review” OR “quantitative review” OR “evidence-based review”

24. How to disambiguate
Enter the general term (polysemic term) into a search box and review the citations
Note any more specific version phrases
See if they meet the criteria of the search intent
create a list of these more specific phrases
Recursively enter the polysemic term NOT the list of specific phrases
Review the outcome to see if there are any more specific phrases

25. Exhaust the possibilities of using a disambiguated polysemic term
Repeat the search using the polysemic term ensuring that there are no citations that only can be found using the polysemic term
If any citations do not have a more specific expression and only the polysemic term can locate it, see if there is something unique in the grammatical expression which can be used as a unique identifier
For example, “search for a review” OR “conduct a review”

26. Validate the disambiguated search terms
Use the Boolean Subtraction Procedure to see if each of the disambiguated search terms is necessary

27. Developing Precision in the Search Filter
3. Use of the Boolean operator NOT
Acronyms in particular are prone to multiple meanings
A way to eliminate non-relevant citations is to subtract the non-relevant ones out
For example
ASD refers to autism spectrum disorder but also many other conditions such as Alzheimer Dementia
So use ASD NOT “Alzheimer Dementia”

28. Developing Precision in the Search Filter
4. enter a series of search filters
multiple search filters are common in a real world search
For example, in looking for systematic review articles on applied behavior analysis with children with autism a number of filters are used “
Autism
Children
Applied behavior analysis
Systematic review
These are all connected in a search with AND, i.e., autism AND Children AND “applied behavior analysis AND “systematic review”

29. Developing Precision in the Search Filter
Each time a search filter is added to the list the search will become more focused, i.e., more precise according to the search intent

30. External Validation of the Pearl Harvested Search Filter
It is important to see if the search does what it is supposed to – find as many relevant citations as possible
Pearl Harvesting uses what is termed a quasi-gold standard reference base as a check to see if can locate a variety of relevant known citations

31. External Validation of the Pearl Harvested Search Filter
Quasi-gold standard reference base
Choose one or more systematic reviews or meta-analyses on the topic being investigated; preferably ones that have not been used in the search term development process
1. analyze the search terms and subject headings used to see if there are any terms not already used
If so test these terms using the Boolean Subtraction Procedure

32. External Validation of the Pearl Harvested Search Filter
Locate the original source studies of the systematic reviews in one of the databases being used for the investigation
Check to see if the Pearl Harvesting Search Filter could locate each of these studies by analyzing their title, abstract and keywords/subject headings
If unable to locate an article look for unique and relevant identifying linguistic markers in the bibliographic information
Test those linguistic markers as to their capably to find unique and relevant citations using the Boolean Subtraction Procedure
If the newly found linguistic marker locates unique and relevant citations add it to the search filter

33. Choosing databases to search
It is well established that a comprehensive search requires searching in multiple databases - not just one
However, there is no theory or systematic approach at the present time for determining which databases to use ju

34. Databases
There are numerous databases and no theory as to which ones to choose in doing a comprehensive review.
Some examples are: ERIC, PsycINFO , Web of Sceince, Google Scholar , Summan

35. Choosing databases to search
A Pearl Harvesting suggestion
Locate systematic reviews in the area being investigated
Review the journals used in the original source studies
Locate the databases that these journals are indexed in
Use these as the sources to search in

36. Choosing databases to search
Note that each database will have some different journals therefore different articles
The number of citations found for each term will therefore vary across databases
Also note, different databases have different search engines so merely copying and pasting the Pearl Harvested search filter into various databases will not work efficiently

37. Polysemic searching
Polysemic terms are general with many possible connotation
For example, review, analysis, synthesis
They are very genera and not precisel when used in a search
Google and Google Scholar only allow a limited number of search terms in one search (32), so the full extent of a Pearl Harvested filter is not possible
Polysemic terms if used in combination with a series of search filters may prove to be easier to implement without too much loss of precison in these databases

38. Pearl Harvesting Information Search Thesaurus
Lists examples of search filters
The search filter can be copied and pasted into appropriate databases
Lists published articles on Pearl Harvesting
Locate the thesaurus by typing into Google: Pearl Harvesting Search Thesaurus
or use the URL below