@gidyn wrote:
@rslade wrote:
Which of the following has the objective to control and manage data from a
central location?
a. Databases
b. Data dictionaries
c. Data access methods
d. Data storage
Answer: b.
Please pardon my ignorance, why b more than a?
A database is simply an organized, searchable file of records containing data elements, each element configured for required and allowable values, including length, character content, embedded file types allowed, etc.
A data dictionary is a meta-document describing in great detail the parameters and uses for named data elements. Data dictionaries are essential to translating across similar, or perceived identical, data elements across databases.
For instance in the USA we have governmental subdivisions, States, some of which officially call themselves commonwealths. A data dictionary would describe the data element STATE as referring only to any one of the 50 States & Commonwealths; the 50 States & Commonwealths plus the District of Columbia; the 50 States & Commonwealths, District of Columbia, plus US territories; or the 50 States & Commonwealths, District of Columbia, US Territories, and US Protectorates; or the 50 States & Commonwealths, District of Columbia, US Territories, and US Protectorates, as well as all recognized Native American (Indian) reservations or territories.
Further, the data dictionary would list the various allowed values for the data element field, with instructions for translation if a given database does not allow all of those options. For State, the sets of allowed values are the full spelled out name, e.g. Connecticut, New Mexico, Alaska; the two-character US Postal System code, e.g. CT, NM, AK; the traditional abbreviations, e.g. Conn., N.M. or N. Mex., Alaska; ANSI 2-digit codes, e.g. 09, 35, 02. (https://en.wikipedia.org/wiki/List_of_U.S._state_and_territory_abbreviations)
Data dictionaries describing the various allowed or possible values for a given data element are essential for central management across multiple cross-linked or communicating databases, and affect both the DB-to-DB interfaces of code as well as influencing the human-computer interface design for optimum usability and utility of the overall system. For instance, the screen interface for the States field may be a dropdown pick-list displaying the fully spelled out names for human users to see, but a translation table would store the two-digit ANSI code in the record for each selection.
Craig
