Enterprise Object Framework

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Enterprise Object Framework
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What is EOF?

• Enterprise Objects Framework is a set of tools
  and resources that help you create applications
  that work with the most popular relational
  databasesor with your own custom data store.
• Enterprise Objects Framework lets you design
  object-oriented database applications that are
  easy to build and maintain and that draw upon
  standard user interface features.
• EOF Developers Guide.pdf

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Problems Addressed

• SQL Object Oriented Paradigm
• Reusability
• Maintainability
• Scalability
• Interactivity
• Portability
• Transaction Support

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Business Logic

• Implementation in 4GL
• Limited reuse
• Not maintainable
• Different implementations
• Poor data integrity
• Doesnt scale well
• Implementation in DB
• Limited interactivity
• No back-end portability
• SQL is a poor development language

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..or Enterprise Object Framework

• Provides
• Encapsulation
• Reuse
• A more natural model of the real world.
• Database-to-object mapping
• Object-to-interface mapping

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What is an Enterprise Object?

• Properties that map to stored or persistent data.
• Knows how to interact with WebObjects to give and
  receive values for its properties.
• Contains business logic for an application.
• Provides an access layer for an application that
  resides just above the database.

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From Database to Object

• Correspondence between database tables and
  enterprise object classes .
• Database rows map to instances of the appropriate
  class.

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Flexibility

• Objects can map to tables, subsets of tables, or
  across tables.
• Object properties can map to one column, or to a
  derived column.
• Object inheritance hierarchy can be mapped to one
  or more database tables.
• to-one and to-many relations provided.

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Relations

• To-one
• To-many

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Uniquing

• Ensures that the mapping of each enterprise
  object to row in a database table is one-to-one.
• Limits memory usage.
• Ensures data integrity.

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Uniquing Example
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Relationships and Faulting

• Resolution of relationships during fetching
• Faults as stand-ins
• Tuning relationship resolution
• Pre-fetching
• Batch faulting

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From Objects to Database

• Validation
• Referential integrity enforcement
• To-one Mandatory vs. Optional
• Delete cascading vs. nullify vs. deny
• Automatic primary and foreign key generation
• Transaction management
• Locking
• Pessimistic, optimistic, on-demand

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From Objects to Interface

• Changes made from the interface by the user are
  automatically synchronized with the enterprise
  objects.
• Changes made to the enterprise objects
  automatically updates the user interface to
  reflect these changes.

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Ingredients for an EOF Application

• A user interface
• A model
• Enterprise Objects
• EOFs classes and interfaces
• A database server and adapter.

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Ingredients (Cont.)
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Components involved

• Access layer Fetches rows from the database and
  tranforms them into enterprise objects.
  Registers the enterprise objects with the control
  layer.
• Control layer Manages the graph of enterprise
  objects in memory, tracking changes made to them,
  and messaging the access layer to commit changes.

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Components (Cont.)

• Interface layer Maps data between the control
  layer and the applications user interface as
  designed with an SDK (such as Java or AppKit from
  Apple).
• WebObjects Combines the use of an interface SDK
  and the interface layer to present the
  application with an HTML interface over the web.

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Access Layer

• Adapter layer Classes that connect with
  specific databases.
• Database layer Classes that create enterprise
  objects from the data source.
• Modeling classes Supplies database login
  information and database to object mappings.

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Control Layer

• EOObjectStoreCoordinator manages interactions
  with the access layer
• EOEditingContext manages graphs of enterprise
  objects and track changes made.

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EOModeler

• Application
• Automation
• Demonstration

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References

• 1http//developer.apple.com/techpubs/webobjects/
  WebObjects_4.5/System/Documentation/Developer/Ente
  rpriseObjects/DevGuide/EOFDevGuide.pdf
• 2http//developer.apple.com/techpubs/webobjects/
  WebObjects_4.5/System/Documentation/Developer/Ente
  rpriseObjects/EOTools/EOToolsAndTech.pdf
• 3http//developer.apple.com/techpubs/webobjects/
  WebObjectsOverview/WebObjects_Overview.pdf
• 4http//developer.apple.com/techpubs/webobjects/
  DiscoveringWO/webobjectsforhtml.pdf
• 5http//developer.apple.com/techpubs/webobjects/
  GettingStartedOnWindows/WOGettingStarted.pdf
• All images presented from 1