Delphi 2 - Delphi Client/Server Suite 2.0 Client/Server Database Architecture

By: Lance Devin

Abstract: Delphi Client /Server Suite incorporates integrated technologies that help solve your business needs.

Delphi Client / Server Suite 2.0
Client/Server Database Architecture (cont.)

2 .Implementation: Data Modules, Scaleable Data Dictionary, Object Repository, and Visual Form Inheritance

2. Implementation:
Data Modules, Scaleable Data Dictionary, Object Repository, and Visual Form Inheritance

a) Data Module Objects

Delphi Client / Server Suite 2.0's Data Module Objects act as your applications information core by providing a designated central location for defining data access and business rules. The Data Module Object separates business logic from the GUI and acts as a codeless way to connect and manage this business logic from a single location.

Delphi Client / Server Suite 2.0's new Data Module Objects encapsulate Business Rules.
  • Business logic can be applied to Tables, Stored Procedures, and Queries by creating methods on Before and After events such as posts, deletes, inserts and edits. This allows you to create new business objects more easily.

  • Master Detail Data relationships are defined in a codeless manner in Delphi. The Developer can create Client / Server applications easily and quickly by visually setting properties on the Datasources or by using the Database Form Expert.

  • Applications and forms can be visually linked to the Data Module to propagate business logic without writing extra code.

  • Data Modules are classes of objects that pertain to the interaction of data with the database server. Isolating all database operations in Client / Server application makes application maintenance simple.

Logical Application Distribution:

The Data Module allows developers to create a logical n-tier application environment by centrally locating business logic and separating it from the GUI and database design. This is a solid foundation for physical support of distributed applications. Support for physical n-tier application and server architectures is currently available for Delphi through third party libraries such as IBM's CICS, ATT's TopEnd, Novell's Tuxedo, Digital's Object Broker, Orbix's IONA and others.

Network OLE and VB4's Remote Automation technology:

In the Windows environment, Microsoft operating system technologies such as Visual Basic 4.0's remote automation and the forthcoming Network OLE can be used to distribute application logic among servers. Because Delphi Client / Server Suite 2.0 fully supports these technologies and can create high performance OLE automation controllers and servers, Delphi will allow developers to create partitioned applications easily.

B) Scaleable Database Dictionary

The database dictionary stores and uses customized information about the contents of the data in your tables. The dictionary ties the familiar model of working with fields through the property inspector to a permanent storage facility. The data dictionary holds information about extended field attributes like min, max, default values, and display preferences. Using the data dictionary has two advantages:

  1. Consistency: common field attributes are centrally stored in the data dictionary and then retrieved at application design time. A developer can create extended field attribute domains and the team can appropriately apply them to fields.

  2. Network Traffic Reduction: Delphi allows for data validation at the client or at the server. The data dictionary can maintain extended field attributes that perform client side data validation efficiently by reducing network traffic.

The Scaleable Data Dictionary maintains consistency by storing attribute sets for Database Schema.

c) Object Repository

Delphi Client / Server Suite 2.0's Object Repository stores and manages application objects: Forms, Data Modules, Experts, and DLLs. In essence, it centrally locates corporate assets so that they may be leveraged by the team to eliminate redundant development efforts. As objects proliferate, the repository increases in importance.

The Object Repository:

  • Supports team development practices by referencing objects on a network.

  • Is customizable so that developers can define their own logical groupings of objects to facilitate reuse.

Object Repository centrally locates application objects and enhances team development.

d) Visual Form Inheritance and Form Linking

Developing a corporate standard in applications is important. Ensuring that these standards are adhered to is more difficult. Visual Form Inheritance and Form Linking extends object oriented programming to a visual paradigm ensuring that corporate and programmatic standards are maintained from project to project. In conjunction with the Object Repository, these standards are centrally managed resulting in faster project turn-around time.

Visual Form Inheritance allows anyone to take advantage of object-oriented reusability and maintainability by providing a codeless way to use inheritance, encapsulation and polymorphism.

Visual Form Inheritance simplifies Object Oriented reusability.

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