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Model and Supporting Environment

Junichi Furukawa

Scho ol of Scho ol of Information Science,

Japan Advanced Institute of Science and Technology

February 13,1998

Keywords: Object-Oriented, Formal Model, Supp orting Environment.

Recently Object-oriented methodologies are focused and used to develop large-scale

systems. OMT is typical of them. OMT consists of three point of views : structural

(ObjectModel),behavioral(DynamicMo del)andfunctional(FunctionalModel). Though

thesethreemodels aredesirable fordescribingsystems, syntaxandsemantics ofthemare

not dened strictly. This makesit diculttosupport modeling with computer.

Aoki prop osedFomal Object0orientedAnal ysisModel(calledFO8M)tosolvethe

problem. FO8M provides indep endent three formal models (called basic model s) and

a mechanism to unify them (called interpr etation). These enable us to treat systems

formally and make it easy to support with computer. However, only static relations are

dened inFO8M,so a metho dfor constructing models must bedened.

In thispaper,amethodforconstructingmodels basedonconceptionsofFO8Mand a

supportingenvironmentforFO8Mareproposed. Atrst,staticrel ationsamongelements

in eachmo del are fo cused. A staticrel ation isa relation which mustbe satised nally.

For example, when an inheritance is dened in the basic object model, it must be also

denedb etweentwoidentiersofthe classes. Next, scoperul es,whichareneed todene

interpretation,arefocused. Attributionsandfunctionsareencapsulatedaccordingtotheir

propertiesin basic objectmodel. Information hidingisrealized byscope r ules whichare

dened according to structure of these objects. So elements in basic object model must

be selected along these rules when interpretation dened. Finally, order of decision is

dened. There area lotof waystoconstruct models. Butelementswhichcan b e decided

after denition of a certain element are limited. Furthermore, there is an order which

must be kept whicheverway is selected. For example, if anidentier of a certainclass is

dened,wecan decidea relationship between it and identier of other classes ora setof

attributes (or functions) correspond to it.

Copyrightc 1998byJunichiFurukawa

rules. In this environment, static rel ations b ecome indices of completeness of mod-

els, scope rul es b ecome metho d to give usable elements in basic object mo del and

order of decision givesusers guidelines on mo del construction.

It's impossible tograsp and extract wholeconcepts in the sp ecication when weana-

lyzelarge-scale systems. Soit'sdesirabletophase andbeable tokeepinformation about

incomplete models. Hence I intro ducerelational database system to keep these informa-

tion. Persistencyof datais insuredthanks todatabase system, too. In database, asetof

identiersdenedinFO8Misgivenasatable. This tablemusthaveenoughinformations

toknowtheelement'sstateandtodistinguisheachother. Primarykeyshouldbedeclared

if a row(s) in the table must have unique value. Now think about a table stands for a

set of identiers of inheritance, for example. An inheritance is a relation b etween two

identiers of class, so a table of them needs rows for these twoidentiers and one more

row for it'sown identier. An identier of inheritance musthave unique value, soit will

be the primary key of this table.

Because there are p ossibilities that many items will disappear by deleting only one

item,wemustb ecareful whendeleteitemsfromthedatabase. Forexample,assumeif an

identier of class isdeleted, relations referto that identier disappear at the same time.

This results disappearance of elements,which never need to be deleted, and unexp ected

collapse of models. So an appropriatepolicyabout deletion mustbe shaped. To protect

this spreading of deletion, I intro duce a special identier Undef. If an element which

constructs the denition of a relation is deleted, a structure of the relation will still

remain. A denition with Undef indicates they are still in incomplete state. So it is

possibletopromoteuserstomakeincompletepartsofmodelsbypointingouttheUndef.

I show how to construct environment with Java as an example. Using Java has

the advantage of corresponding to multi-platform and good connectivity with database

system thanks to JDBC API.

We need some guidelines on process of construction along architecture of FO8M in

addition tostaticr elationsandscoper ule. Theorder of decisionisdenedtoformalize

them. Using relations and rules, dened above, we can get indices and guidelines of

making mo del.

Database system isuseful to keepinformation of models but denitionof tables must

be done carefully with taking inuence of deleting items into account. An inuence of

deletion islimitedbyintro ducing aspecial identier,Undef. Datastoredindatabase are

very imp ortant because they will be used inother supporting environment for FO8M or

other phases afteranalysis.