ANSI ISO IEC-11179-1-1999 pdf download Information technology — Specification and standardization of data elements — Part 1: Framework for the specification and standardization of data elements
5. Methodology Independence
Itisrecognizedthat different methodologiesareusedtoderiveapplication-orienteddataelements. Data modeling, alone, hasnumerousmethodological approaches(e.g., InformationEngineeringandobject-oriented) for identifyingandformingdataelements. Thisdataspecificationstandard, includingitssixparts, is independent of anydataelement derivationmethodologyor technique. Sincethestandardappliestoall data elements, itcanbeusedequally well inanyapproachtodataelement creation.
6. Fundamental Concepts of Data Elements
Forthepurposesof ISO/IEC11179, adataelement iscomposedof threepartsasfollows:
· theobject class isasetof ideas, abstractions, orthingsinthereal worldthat canbeidentifiedwith explicit boundariesandmeaningandwhosepropertiesandbehavior followthesamerules;
· theproperty isapeculiaritycommontoall membersof anobjectclass; and
· therepresentation describeshowthedataarerepresented, i.e. thecombinationof avaluedomain, datatype, and, if necessary, aunit of measureoracharacterset.
Objectclassesarethethingsabout whichwewishtocollect andstoredata. Examplesof objectclassesarecars, persons, households, employees, orders, etc. However, it isimportant todistinguishtheactual objectclassfrom itsname. Ideassimplyexpressedinonenatural language(English), maybemoredifficultinanother (Chinese), andvice-versa. Forexample, “womenbetweentheagesof 15 and45 whohavehadatleast onelivebirthinthe last 12 months”isavalidobject classnoteasilynamedinEnglish. Nevertheless, object classescanbeformed bycombiningtwoor moreother objectclasses. Thisexamplecombinesthenotionsof “peoplebetweentheages of 15 and45″ with”womenwhohavehadat leastonelivebirthinthelast 12 months”.
Propertiesarewhat humansusetodistinguishor describeobjects. Examplesof propertiesarecolor, model, sex, age, income, address, price, etc. Again, propertiesmayneedtobedescribedusingmultiplewords, dependingon thenatural languageinuse. Themostimportantaspect of therepresentationpart of adataelement isthevaluedomain. A value domain isa set of permissible(or valid) valuesfor adataelement.
Forexample, thedataelementrepresentingannual householdincome 1 may havetheset of non-negativeintegers(withunitsof dollars) asaset of validvalues. Thisisanexampleof anon-enumerated domain. Alternatively, thevalidvaluesmaybeapre-specifiedlistof categorieswithsomeidentifier foreachcategory, suchas:
1 $0 – $15,000
2 $15,001 – $30,000
3 $30,001 – $60,000
4 $60,001 – +
Thisvaluedomainisanexampleof anenumerated domain. Inbothcases, thesameobjectclassandproperty combination – theannual incomefor ahousehold- isbeingmeasured.
Thecombinationof anobjectclassandapropertyisadata element concept (DEC). A DECisaconceptthat canberepresentedintheformof adataelement, describedindependentlyof anyparticular representation. In theexamplesabove, annual householdincomeactuallynamesaDEC, whichhastwopossiblerepresentations associatedwithit. Therefore, adataelementcanalsobeseentobecomposedof twoparts:adataelement concept andarepresentation. Figure6-1 illustratestheideasconveyedinthissection.
ANSI ISO IEC-11179-1-1999 pdf download
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