Generic Modeling

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Generic Modeling

Copyright 2011, Oracle. All rights reserved.

Generic Modeling


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Generic Modeling


What Will I Learn?ObjectivesIn this lesson, you will learn to:

Define generic modeling Evaluate and describe the advantages

and disadvantages of generic modeling Construct a generic version of a more

specific data model


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Generic Modeling


Why Learn It?

Purpose

Generic models can reduce the number ofentities in a diagram and provide a lot offlexibility in unstable situations, where thebusiness requirements change often.

A business that needs to frequently addentities and/or attributes could benefit fromgeneric modeling. One example would bea pawnshop that buys and sells different

types of items all the time. It would bedifficult to predict the number of item typesand the different attributes each typewould have.

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Tell Me / Show Me

GenericModelingGenericmodeling looksat the same

context fromanother, moredistantperspective.From a distance,

many things lookthe same.

MANUFACTURER

# name

ARTICLE TYPE# name

ARTICLE

# id* length* material waistband type bodice cut hem circumference neck size sleeve length

MANUFACTURER

# name

SHIRT* id* length* material* neck size

* sleeve length

SKIRT# id

* length* material* waistband type* hem circum

DRESS# id* length* material* bodice style

PANTS# id* length* material waistband type

produced

theproducer

produced classified

GENERIC MODEL

theproducer


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Generic Modeling


Tell Me / Show MeChoosing a Generic ModelSuppose you are to make a model for aclothing store. The business typically sellsmany different articles: shoes, shirts, dresses,pants, and so on. For each type of clothing

article, there are different attributes. You canmodel every type as an entity. Or you couldcreate a more generic model that uses oneentity, ARTICLE, with or without subtypes.

However, this model would be fine only ifthere were no (or possibly very few) newinstances of ARTICLE TYPE during the lifecycle of the system.


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Generic Modeling


Tell Me / Show Me

Recycling of Attributes Another generic modelinvolves recyclingattributes.

Using this structure, hereare some examples ofinstances of ARTICLETYPE:

the classificationfor

classifiedby

the producer of

producedby

ARTICLE TYPE# name* definition of Prop. 1* definition of Prop. 2* definition of Prop. 3o definition of Prop. 4

MANUFACTURER# name

VALUE* value of Prop. 1* value of Prop. 2* value of Prop. 3o value of Prop. 4o value of Prop. 5

o value of Prop. 6o value of Prop. 7


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Generic Modeling


Tell Me / Show MeRecycling of Attributes (continued)

Name Def. ofProp. 1

Def. of Prop2

Def. ofProp 3

Def ofProp 4

Def ofProp 5

SHIRT id Length Material Neck Size SleeveLength

SKIRT Id Length Material WaistbandType

HemCircum.

DRESS id Length Material BodiceStyle

PANT id Length Material WaistbandType

You can also store information about the data types of eachproperty in the definition attributes (example: property 2 for allarticles (length) has a data type of number, property 4 ofDRESS (bodice style) is stored as text).


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Tell Me / Show MeExampleThese would be the examples of corresponding instances of

ARTICLE.

the classificationfor

classifiedby

the producer of

producedby

ARTICLE TYPE# name* definition of Prop. 1* definition of Prop. 2* definition of Prop. 3o definition of Prop. 4

MANUFACTURER

# name

VALUE

* value of Prop. 1* value of Prop. 2* value of Prop. 3o value of Prop. 4o value of Prop. 5o value of Prop. 6o value of Prop. 7


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Tell Me / Show MeGeneric ValuesUsing this method, you can add new types of articles fairlyeasily, provided that the number of attributes does not exceedthe maximum that was originally defined.

ARTICLETYPE

Name

Def. ofProp. 1

Def. ofProp 2

Def. ofProp 3

Def ofProp 4

Def ofProp 5

SHIRT DNM105 40 Denim 16 33

SKIRT LIN200 22 Linen Elastic 60

DRESS SHF119 60 Jersey Empire

PANT CHN407 33 Khaki Flat Front


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Tell Me / Show MeAttributes Modeled as

Property Instance

This model takes a thirdapproach. Every value for aproperty of an ARTICLE isstored separately. This modelgives a lot of freedom to definenew articles and propertiesduring the life cycle of thesystem.

Using this structure, here aresome examples of instances ofeach entity:

ARTICLE PROPERTY VALUE* value

ARTICLE# id

PROPERTY# number

MANUFACTURER* name

ARTICLE TYPE# name

theproducer

of

producedby

theclassification

for

classifiedby

theowner

of

ownedby

theholder

of

heldby

containedin

the

containerfor


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Tell Me / Show Me

Name

SKIRT

SHIRT

DRESSPANT

ARTICLE TYPEArticleType Name

No. Desc.

SHIRT 1 Length

SHIRT 2 Material

SHIRT 3 Neck size

SKIRT 1 Length

PROPERTY

Article TypeName

Id

SHIRT DNM105

SKIRT LIN200

DRESS SHF119

PANTS CHN407

ARTICLE

Article ID Article Type Name PROPERTY Number Value

DNM105 SHIRT 1 40

DNM105 SHIRT 2 DenimDNM105 SHIRT 3 16

LIN200 SKIRT 1 22

ARTICLE PROPERTY VALUE

Attributes Modeled as Property Instance (continued)


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Tell Me / Show MeGeneric Model Benefits

The benefits of a generic model include:

(1) Flexible -- can prevent the need tochange data structures in the future

(2) Can reduce the number of entitiesdramatically

Cost: Increased complexity in both the datamodel and application programs

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Tell Me / Show MeTerminologyKey terms used in this lesson include:

GenericPerspective


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Objectives SummarizedIn this lesson, you have learned to: Define generic modeling Evaluate and describe the advantages and

disadvantages of generic modeling Construct a generic version of a more specific data

model

Summary


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Generic Modeling

C i h 2011 O l All i h d

Practice GuideThe link for the lesson practice guide can be found inthe course resources in Section 0.

Summary

Documents

Generic Modeling