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A search can be narrowed down by focusing it on the different fields of the record. Normally, databases offer search forms in which fields can be selected from drop-down menus, or search boxes are offered in which command searches and codes for field restrictions can be used. The contents of the fields must always be checked from the instructions of the database, because the fields have different names depending on the databases and user interfaces. Databases may have field specific alphabetical indices of the words fed into the fields.
On the Advanced Search search form in the ProQuest interface, the field code can be selected from a drop-down menu. The field Anywhere except full text focuses the search simultaneously on all fields and field Anywhere also on full texts in full text providing databases. Image source: ProQuest <http://search.proquest.com> 25.7.2013
A command search often offers more fields than the drop-down menu in the search form. When a search form allows simultaneous searches in several databases, it is worth remembering that not all databases necessarily contain the same fields. For example, Article Taxonomic Terms (ATX) is not in use in all ProQuest databases. Image source: ProQuest <http://search.proquest.com> 25.7.2013
Normally, the databases used in a search contain reference information about books or journal articles, abstracts and often a full text or a link to an electronic version of a publication. Depending on the discipline, databases may contain, for example, formulae of chemical compounds, DNA sequences or images. More often than not, reference databases contain at least the following centrally important search fields:
TI: An organizational decision support system for effective R and D project selection
AU: Tian, Qijia; Ma, Jian; Liang, Jiazhi; Kwok, Ron C. W.; Liu, Ou
SO: Decision Support Systems, v 39, n 3, May, 2005, p 403-413
Publication/ Document type
AB: Research and development (R and D) project selection is an important task for organizations with R and D project management. It is a complicated multi-stage decision-making process, which involves groups of decision makers ...
Descriptors, Index Terms, Subject, Identifiers etc.
DE: Studies, Decision support systems, Research & development, R&D, Decision making, Systems design, Object oriented programming
CL: 9130 Experim./theoretical, 5240 Software & systems, 5400 Research & development
Free Text Search
In a Free Text Search, the search terms can be chosen freely, and the search in a database can be focused on all searchable fields of the record, even on the full text in some databases. It is worth using a full text search when looking for factual information, or when the topic is well defined, or it is otherwise difficult to find information on. In addition to natural language, everyday language, professional vocabulary and proper names, terms found from thesauruses can be used in a Free Text Search. When focused on all search fields, a Free Text Search can produce a large search result containing also irrelevant references.
When searching for information on a particular topic with a Free Text Search, in general it is advisable to limit the search to the most important fields from the point of view of the subject matter, i.e. the title, abstract and descriptor fields.
A Free Text Search focused on all fields using the term "decision support system*" produces references where the search terms can appear in any field: in the example reference, the term can be found in the document title, the Publication title, the Abstract and the Subjects.
Image source: ProQuest <http://search.proquest.com> 5.7.2013
Subject Heading Search
Databases often use an established subject index or thesaurus. When a document, for example an article, is added to a database, its most essential contents are described with terms chosen from the thesaurus and these terms are entered in the subject term field (Descriptors, Controlled terms, Index terms..) of the reference. Database interfaces normally offer an option for a Subject Heading Search which allows you to limit the search to subject (descriptor) fields. The purpose of creating descriptors is to help those in need of information to find relevant references.
A Subject Heading Search looks for the terms decision support systems only in the Subjects field.
Image source: ProQuest <http://search.proquest.com> 26.7.2013..
In the thesaurus of the Abi/Inform database you can select "decision support systems" term and perform subject seach by clicking "Add to seach" button. Image source: ProQuest <http://search.proquest.com> 1.7.2013.
In many databases, classification systems are also used for describing the contents of documents. The classification codes can be seen in each record in its own field (classification codes, cc, ....) and these can also be made use of in information retrieval when focusing the search.
MathSciNet database uses MSC Classification (Mathematics Subject Classification). A classification search provides you with references, where in the 'classification codes' field we retrieve results containing the code 60.65. Image source: MathSciNet<http://www.ams.org/mathscinet/> 2.7.2013