Presentation on theme: "Lecture 3 Database Structure, Organization and Selection (cont’d)"— Presentation transcript:
Lecture 3 Database Structure, Organization and Selection (cont’d)
Designing A Database Which fields in the records will be searchable What type of Indexing Special characters LIMIT capabilities Pre-defined display formats
? Words or phrases are removed and entered into an alphabetical list so that they can be searched separately. Each searchable field is indexed
Selecting a Database Use Documentation - Vendor/Producer DIALINDEX/CROS Article or database labels Familiarity with printed tool
Things to Consider Subject Coverage - Size, comprehensiveness (selective? (F/S)), only major articles, number and type of periodicals/books/materials (research, popular, non-print, reports), international v. National Years Searchable - Variable from system to system. Some vendors may have all years in one file (MEDL)
Considerations (cont’d) Years Searchable - Other vendors may require you repeat search for each segment. Some smaller files do go back (Diss Abs, MAGS, SPORT). Always some patron who want to go back 50-100 years! Thesaurus vs. Uncontrolled Vocabulary - lecture on the differences next class mtg. But having controlled vocabularly features can be extremely useful or even necessary for many searches
Considerations (cont’d) Type of Information desired - fulltext, data, WWW, mtg. abs., books, A-V’s, etc. Cost - Might avoid use of expensive files if patron won’t pay (MEDL vs. BIOSIS, SPORT) Searchable Parameters - Search author addresses? Volume and page numbers? Remove previous results? Formulas? Limit to specific time periods?
Considerations (cont’d) Currency - Update schedule (local/cd- rom/web vs. online), lag time Are References Easily Obtainable - everything ILL? Most are here? Now, WWW for TRAC, Fulltext online? Printed Version - Could have patron use printed tool and do online for unavailable or could used printed to help
Considerations (cont’d) Familiarity/Frequency of Use - the more you use it, the more you learn the idiosyncrasies, the better you search it. On a vendor rarely used, you may not be effective. Select one you are comfortable with if it serves the purpose. Much literature written comparing coverage and searching databases.
Considerations (cont’d) Special Features - labels? Reports? Rank results? Cited references? Lot of overlap in some areas but you will always find unique items for each database due to one or more of the above factors. Vendors supply documentation in support/marketing of their products. The “big” vendors give you “cheat sheets” as well as detailed, in-depth information. Manipulate the data.
Considerations (cont’d) Size of Retrieval - 5000! Or search statements Online Vocabulary/Dictionary Online DialIndex/CROS - allows for entering of search statements and system simultaneously searches groups of databases - then, select file with highest postings
Considerations (cont’d) Read Chapters - When in doubt, consult database chapters that are very detailed and descriptive. Supplied by vendor. Give search hints, provide special codes, offer exampes, but most important, UNIT RECORD!!!! What is a unit record?
When is the Same Database Not the Same? Years of Coverage - CD-ROM vs. Online Comprehensiveness - CD-ROM absent of certain material in online source such as books/dissertations in SocioAbs and PsycInfo. (PsycLit has a unique book chapter file on cd-rom product - not available online. BIOSIS on F/S is only the subset of online file; PsycFirst is only a ‘baby’ file. H-L WWW site v. File 721 (Obits, columns)
When is the Same Database Not the Same? (cont’d) Parsing - text-editing, etc. What is a word? Single character? Stopwords? Unit Record? Field Searchable? Standardization (IBM or I.B.M.)? Basic Index? Pricing - Live time? Volume discount? Flat-fee? More for different formats? Time to process search? Non-prime time? DialUnit?
When is the Same Database Not the Same? (cont’d) Updating/Currency - daily, hourly, weekly, monthly, quarterly, annually?? AMWS = biannual update. Is there a delay after the tapes are rec’d? (MEDL on NOTIS). Producer/vendor have updates first before the competition
When is the Same Database Not the Same? (cont’d) How vendor mounts subfiles Vocabulary Online Unit Record Loading - Fields may not be searchable but merely displayable (AN, AU address/affiliation, etc.) Special Search Features - Explosions on SP MEDL lost on MDAS MEDL; Multi-file searching; GUI interface
When is the Same Database Not the Same? (cont’d) Reloads - YR becomes PY; different segments may be searched differently Basic Search Engine - “adj”, “with”, “link” operator. Few characters/stopwords that cannot be searched? Basic index?
Producers: Sources of Errors (What else can go wrong?) Indexers - (dogs-tu!); misspellings; omissions (automatic checktags) Enhancing or improving database - New features start from that point and don’t go back to the earlier years (YR vs. PY)
Producers: Sources of Errors (What else can go wrong?) Lack of Standardization - AU names in ERIC or BIP *brewer-ra *brewer-rick-a *brewer-rick-allen Spelling - British and Canadian databases