Selecting Objects An OO Architecture of the Relational Model

1
Selecting ObjectsAn OO Architecture of the
Relational Model

• Polina Cherkasova
• Saint-Petersburg, 2005

2
The Relational and OO models

• OO designing
• Relational performance
• ? Impedance Mismatch

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Logical Levels

• User Interface
• Business Functionality
• Data Structures

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Logical Levels

• User Interface
• Business Functionality
• Data Structures
• Relations
• Attributes of objects
• XML structures

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Logical Levels

• User Interface
• Business Functionality
• Functions, Procedures, Views, Triggers
• Object methods
• Middle tier in the Three-Tier mofdel
• Data Structures

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Logical Levels

• User Interface
• Web Applications
• Stand-Alone Application
• Web Service
• Business Functionality
• Data Structures

7
N
S
8

• One by one
• StartTime
• S ln(N)
• S (
• StartTime
• ln(N)
• UpdateTime
• )
• _______
• ln(N) S

• Together
• StartTime
• S ln(N)
• S UpdateTime
• _______
• ln(N) S

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Bulk Operations

• Delete
• Move
• Copy
• Template objects
• Import and export
• Explicit multiplicity

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Commonly used approaches

• OO interface
• Call-back from the Data Structures level
• Various data sources

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Commonly used approaches

• OO interface
• ------- ----
• --------
• ----
• --- --- ---- --- --
• -----
• -------
• --------
• -
• Call-back from the Data Structures level
• Various data sources

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Commonly used approaches

• OO interface
• Call-back from the Data Structures level
• Various data sources

OnUpdate OnCreate OnDelete
??
??
?????????
?????????
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Commonly used approaches

• OO interface
• Call-back from the Data Structures level
• Various data sources

CreateObject(int a, string b) CreateObject(string
sourceName)
Create object
OK
Cancel
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Selecting Objectsentities and data sets
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Selecting Objectsentities and data sets
Restrictions OO interface Encapsulation of data
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Data Set

• The query is not executed
• The query can be modified
• Data are not accessible

• The query is executed
• Data can be used
• To obtain other data new one more call to the
  database is needed
• If redundant data was requested, spent resources
  can not be recovered

17
Selecting Objects

• OO interface
• Call-back from the Data Structures level
• Various data sources

18
Selecting Objects

• OO interface
• ------- ----
• --------
• ----
• --- --- ---- --- --
• -----
• -------
• --------
• -
• Call-back from the Data Structures level
• Various data sources

19
Selecting Objects

• OO interface
• Call-back from the Data Structures level
• Various data sources

OnUpdate OnCreate OnDelete
??
??
?????????
?????????
20
Commonly used approaches

• OO interface
• Call-back from the Data Structures level
• Various data sources

CreateObject(DataQry qry)
Create object
OK
Cancel
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Data set types

• List of field names
• Base query

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Detailing
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Selection

• SupplierQry qry new SupplierQry()
• qry.Where.And(SupplierQry.Fields.SupplierName "
  like 'A'")
• int count qry.ExecuteCount()

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Updating

• Methods of the class Entity
• InsertRows
• UpdateRows
• DeleteRows

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Triggers

• private void ProcessNewData(SupplierQry inserted)
• SupplierQry wrongSuppliers new
  SupplierQry(inserted)
• wrongSuppliers.Where.And(String.Format("not
  IsValidSupplierName(0)",
• SupplierQry.Fields.SupplierName))
• string expr String.Format("CorrectSupplierNa
  me(0)", SupplierQry.Fields.SupplierN
  ame)
• this.UpdateRowsById(wrongSuppliers,
• Assign.Expression(SupplierQry.Fields.SupplierNa
  me, expr))

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Designing

• Does the truncated object-oriented model still
  make sense?

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Polymorphism and Call-Back
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Inheritance and Reuse
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Encapsulation of Data and Complex Calculations
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Open Issues

• Obtaining and analysis of the practical results
• Atomic parts of an SQL query and their nature.
• Questions of casting of data set types.
• Rules of interaction with application and the
  structure of interface level of Business
  Functionality
• How to mitigate risk of low concurrency 15 due
  to encapsulated data behavior?