CSC/ECE 517 Fall 2009/wiki3 12 Patterns for ORM - Revision history

Pbsingh: /* '''Class Table Inheritance ''' */

2009-11-23T04:01:30Z

'''Class Table Inheritance '''

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	==='''Class Table Inheritance '''===		==='''Class Table Inheritance '''===
	One table for each class is constructed. The advantage of this table inheritance is that there is clear relationship between class and table. There is high normalization. But multiple tables requires join and when fields move up and down in hierarchy, it requires changes in the tables.		One table for each class is constructed. The advantage of this table inheritance is that there is clear relationship between class and table. There is high [http://en.wikipedia.org/wiki/Database_normalization normalization]. But multiple tables requires [http://en.wikipedia.org/wiki/Join_%28SQL%29 join] and when fields move up and down in hierarchy, it requires changes in the tables.

	[[Image:wiki_3_12.jpg]] [[Image:Wiki_3_12_4_.jpg]]		[[Image:wiki_3_12.jpg]] [[Image:Wiki_3_12_4_.jpg]]

Pbsingh: /* '''[http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html Inheritance Mapping]''' */

2009-11-23T04:00:07Z

'''[http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html Inheritance Mapping]'''

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	=='''[http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html Inheritance Mapping]'''==		=='''[http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html Inheritance Mapping]'''==
	[http://en.wikipedia.org/wiki/Inheritance_(object-oriented_programming) Inheritance] in [http://en.wikipedia.org/wiki/Object-oriented_design Object Oriented Design] makes it difficult to map between object and relation databases. In this pattern, there is mapper class for each domain class that will save and load data for the domain class [8]. Mapper class allows both [http://en.wikipedia.org/wiki/Class_%28computer_science%29#Abstract_classes abstract] and concrete classes to handle their own O/R mapping[8].		[http://en.wikipedia.org/wiki/Inheritance_(object-oriented_programming) Inheritance] in [http://en.wikipedia.org/wiki/Object-oriented_design Object Oriented Design] makes it difficult to map between object and relation databases. In this pattern, there is mapper class for each domain class that will save and load data for the domain class [8]. Mapper class allows both [http://en.wikipedia.org/wiki/Class_%28computer_science%29#Abstract_classes abstract] and [http://en.wikipedia.org/wiki/Class_%28computer_science%29#Concrete_classes concrete classes] to handle their own O/R mapping[8].

Pbsingh: /* '''[http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html Inheritance Mapping]''' */

2009-11-23T03:59:28Z

'''[http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html Inheritance Mapping]'''

← Older revision		Revision as of 03:59, 23 November 2009
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	=='''[http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html Inheritance Mapping]'''==		=='''[http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html Inheritance Mapping]'''==
	[http://en.wikipedia.org/wiki/Inheritance_(object-oriented_programming) Inheritance] in [http://en.wikipedia.org/wiki/Object-oriented_design Object Oriented Design] makes it difficult to map between object and relation databases. In this pattern, there is mapper class for each domain class that will save and load data for the domain class [8]. Mapper class allows both abstract and concrete classes to handle their own O/R mapping[8].		[http://en.wikipedia.org/wiki/Inheritance_(object-oriented_programming) Inheritance] in [http://en.wikipedia.org/wiki/Object-oriented_design Object Oriented Design] makes it difficult to map between object and relation databases. In this pattern, there is mapper class for each domain class that will save and load data for the domain class [8]. Mapper class allows both [http://en.wikipedia.org/wiki/Class_%28computer_science%29#Abstract_classes abstract] and concrete classes to handle their own O/R mapping[8].

Quick Gun Murugan: /* '''References''' */

2009-11-22T04:03:21Z

'''References'''

Quick Gun Murugan: /* '''Type Conversion''' */

2009-11-22T04:01:54Z

'''Type Conversion'''

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	=='''Type Conversion'''==		=='''Type Conversion'''==
	There are situations when the values in the database do not map directly to object data types. Take the Boolean data type for example. Boolean values "true" and "false" may be saved as "T" and "F" respectively in the database. Type conversion should be facilitated without any data loss[2].		There are situations when the values in the database do not map directly to object data types. Take the Boolean data type for example. Boolean values "true" and "false" may be saved as "T" and "F" respectively in the database. Type conversion should be facilitated without any data loss[2]. The figure below shows type conversion mapping.
			[[Image:Tcmapfig.jpg]]

	=='''References'''==		=='''References'''==

Quick Gun Murugan: /* '''Type Conversion''' */

2009-11-22T03:58:06Z

'''Type Conversion'''

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	=='''Type Conversion'''==		=='''Type Conversion'''==
	There are situations when the values in the database do not map directly to object data types. Take the Boolean data type for example. Boolean values "true" and "false" may be saved as "T" and "F" respectively in the database. Type conversion should be facilitated without any data loss.		There are situations when the values in the database do not map directly to object data types. Take the Boolean data type for example. Boolean values "true" and "false" may be saved as "T" and "F" respectively in the database. Type conversion should be facilitated without any data loss[2].

	=='''References'''==		=='''References'''==

Quick Gun Murugan: /* '''Foreign key aggregation''' */

2009-11-22T03:40:31Z

'''Foreign key aggregation'''

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	\|align="center"\|Factoring out aggregated objects allows easy querying these tables with ad-hoc queries.		\|align="center"\|Factoring out aggregated objects allows easy querying these tables with ad-hoc queries.
	\|}		\|}

			=='''Type Conversion'''==
			There are situations when the values in the database do not map directly to object data types. Take the Boolean data type for example. Boolean values "true" and "false" may be saved as "T" and "F" respectively in the database. Type conversion should be facilitated without any data loss.

	=='''References'''==		=='''References'''==

Quick Gun Murugan at 03:08, 22 November 2009

2009-11-22T03:08:08Z

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	=='''Overview'''==		=='''Overview'''==
	[http://en.wikipedia.org/wiki/Object-relational_mapping Object-relational mapping] is not trivial. Apart from being based on Software Engineering principles like coupling, cohesion and polymorphism, the object paradigm focuses on building applications out of objects that have both data and behavior. However, the relational paradigm is based on mathematical principles and focuses primarily on storing data. If only data objects were to be mapped to the relational database the procedure would have been fairly straightforward. With the growing complexities of object models, concepts like aggregation, inheritance, polymorphism, association between classes, and data type (smarted than SQL data types) have to be mapped to relational table structure. The table below highlights the fundamental mismatch between object oriented data model and relational data storage.		[http://en.wikipedia.org/wiki/Object-relational_mapping Object-relational mapping] is not trivial. Apart from being based on [http://en.wikipedia.org/wiki/Software_engineering Software Engineering] principles like [http://en.wikipedia.org/wiki/Coupling_(computer_science) coupling], [http://en.wikipedia.org/wiki/Cohesion_(computer_science) cohesion] and [http://en.wikipedia.org/wiki/Polymorphism_in_object-oriented_programming polymorphism], the object paradigm focuses on building applications out of objects that have both data and behavior. However, the relational paradigm is based on mathematical principles and focuses primarily on storing data. If only data objects were to be mapped to the relational database the procedure would have been fairly straightforward. With the growing complexities of object models, concepts like [http://en.wikipedia.org/wiki/Aggregation_(object-oriented_programming) aggregation], [http://en.wikipedia.org/wiki/Inheritance_(object-oriented_programming) inheritance], [http://en.wikipedia.org/wiki/Polymorphism_in_object-oriented_programming polymorphism], association between classes, and data type (smarted than [http://en.wikipedia.org/wiki/SQL SQL] data types) have to be mapped to relational table structure. The table below highlights the fundamental mismatch between object oriented data model and relational data storage.

	{\|border="2" cellspacing="0" cellpadding="4" width="50%" align="center"		{\|border="2" cellspacing="0" cellpadding="4" width="50%" align="center"

Quick Gun Murugan: CSC/ECE 517 Fall 2009/wiki3 12 Patterns for mapping objects to relational databases moved to CSC/ECE 517 Fall 2009/wiki3 12 Patterns for ORM: Link did not appear in Expertiza.

2009-11-20T18:04:47Z

CSC/ECE 517 Fall 2009/wiki3 12 Patterns for mapping objects to relational databases moved to CSC/ECE 517 Fall 2009/wiki3 12 Patterns for ORM: Link did not appear in Expertiza.

← Older revision	Revision as of 18:04, 20 November 2009
(No difference)

Pbsingh: /* '''Many-to-many mapping''' */

2009-11-19T02:06:37Z

'''Many-to-many mapping'''

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	==='''Many-to-many mapping'''===		==='''Many-to-many mapping'''===
	If each record in Table A may links to many records in Table B and vice-versa [10], it’s called Many-to-Many relationships. In ~~fig~~, let’s consider that an employee can work more than one department and department can contain more than one employee.<br>		If each record in Table A may links to many records in Table B and vice-versa [10], it’s called Many-to-Many relationships. In Figure 9, let’s consider that an employee can work more than one department and department can contain more than one employee.<br>
	The Many-to-Many relationships is represented in term of association table. A separate table called association table is created that contains the foreign keys of participating tables [9].		The Many-to-Many relationships is represented in term of association table. A separate table called association table is created that contains the foreign keys of participating tables [9].
			[[Image:Wiki 3 12 7.jpg]]
			Figure 9 : Many-to-many mapping

	=='''[http://en.wikipedia.org/wiki/Aggregation_(object-oriented_programming) Aggregation] Mapping'''==		=='''[http://en.wikipedia.org/wiki/Aggregation_(object-oriented_programming) Aggregation] Mapping'''==

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	=='''References'''==		=='''References'''==
	[1]http://www.objectarchitects.de/ObjectArchitects/orpatterns/<br>		[1] http://www.objectarchitects.de/ObjectArchitects/orpatterns/<br>
	[2]http://subs.emis.de/LNI/Proceedings/Proceedings48/GI.Band.48-6.pdf<br>		[2] http://subs.emis.de/LNI/Proceedings/Proceedings48/GI.Band.48-6.pdf<br>
	[3]http://www.joeyoder.com/Research/objectmappings/Persista.pdf<br>		[3] http://www.joeyoder.com/Research/objectmappings/Persista.pdf<br>
	[4]http://www.ibm.com/developerworks/library/ws-mapping-to-rdb/<br>		[4] http://www.ibm.com/developerworks/library/ws-mapping-to-rdb/<br>
	[5]http://www.dparsons.co.uk/mindthegap.pdf<br>		[5] http://www.dparsons.co.uk/mindthegap.pdf<br>
	[6]http://proceedings.informingscience.org/InSITE2007/IISITv4p767-779Jusi281.pdf<br>		[6] http://proceedings.informingscience.org/InSITE2007/IISITv4p767-779Jusi281.pdf<br>
	[7]http://www.sis.pitt.edu/~gray/INFSCI1025/references/AmblerORMMapping101Article.pdf<br>		[7] http://www.sis.pitt.edu/~gray/INFSCI1025/references/AmblerORMMapping101Article.pdf<br>
	[8]http://www.brettdaniel.com/files/2006/inheritancemapping.ppt<br>		[8] http://www.brettdaniel.com/files/2006/inheritancemapping.ppt<br>
	[9]http://www.objectarchitects.de/ObjectArchitects/orpatterns/index.htm?MappingObjects2Tables/mapping_object.htm<br>		[9] http://www.objectarchitects.de/ObjectArchitects/orpatterns/index.htm?MappingObjects2Tables/mapping_object.htm<br>
	[10]http://databases.about.com/cs/tutorials/a/accessgup7.htm<br>		[10] http://databases.about.com/cs/tutorials/a/accessgup7.htm<br>
	[11]http://www.oracle.com/technology/products/ias/toplink/doc/1013/main/_html/relmapun005.htm<br>		[11] http://www.oracle.com/technology/products/ias/toplink/doc/1013/main/_html/relmapun005.htm<br>
	[12]http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html<br>		[12] http://docs.jboss.org/hibernate/core/3.3/reference/en/html/inheritance.html<br>
			[13] http://wiki.eclipse.org/Introduction_to_Mappings_(ELUG)<br>