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Upgrading and Migrating Siebel Janna Applications > Siebel Janna Terminology and Architecture > Siebel Janna Object Architecture >

Architecture Layers

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Siebel Janna Applications are divided into three logical layers:

Presentation layer
Business layer
Data layer

Each layer is composed of objects. A standard implementation of a Siebel Janna Application uses core Siebel Janna objects to provide a standard Customer Relationship Management solution. Because enterprise requirements are diverse, Siebel Janna Applications allow you to customize objects at each layer and integrate them into Siebel Janna Applications.

The Presentation Layer

The presentation layer allows the user interface (UI) to display or collect data. This layer is also called the front-end layer, or the workflow or presentation logic, of the application. The presentation layer can be Windows-based or Web-based and contains presentation objects which interact with the end user. Presentation objects can be created from ActiveX controls, Active Server Pages, or Java Applets, depending upon whether the platform is Windows-based or Web-based. Siebel Janna Applications use ActiveX controls for presentation objects for the Windows Client and Active Server Pages (with JavaScript and HTML) for presentation objects for the Web Client.

Presentation objects communicate with the rest of the system through requestors. Requestors are COM objects which call other objects in the business layer to perform tasks. They are important because they provide a transparent connection to objects in the business layer, objects which could be local or remote.

The Business Layer

The business layer, also referred to as the application layer, is composed of the following:

Siebel Janna Service Objects
Siebel Janna Listener Objects
Siebel Janna Application Server (SJAS), a component manager
Janna Database Access Objects (SJDAOs)

On a two-tier system, the listener object and the SJAS are not required because object management is done locally by COM. Two-tiered applications usually work very well in departmental-scale applications with modest numbers of users (under 100), a single database, and secure, fast networking. On a three-tier system, the Requestors and listener objects isolate the presentation and business layers from the transport protocol. The independence between the business layer, the presentation layer, and the data layer provides a number of benefits, as follows:

Developers can use powerful development tools such as Visual Basic and Visual C++ to develop reusable application components, instead of using more limited procedural languages.
Administrators can replicate application components to run on multiple machines simultaneously. This configuration spreads client loads across multiple machines. Application component replication (as opposed to data replication) is not possible with two-tiered architectures because stored procedures must run in a single database.
Application components can share database connections. This lowers the number of total sessions that the database server must support. With two-tiered systems, the database must allocate a connection for every user.
Middle-tiered application components can be secured centrally using a common infrastructure. Administrators can grant or deny access on a component-by-component basis.
Access to resources such as mainframe applications and other databases comes through native protocols and application interfaces instead of through data gateways. This allows application owners to control access to their data.

Siebel Janna Service Objects

A Siebel Janna Service Object is an ActiveX component that retrieves and processes data from a database. In a typical n-tier architecture, these objects form the business layer where business rules are enforced.

In the Siebel Janna architecture, the presentation objects communicate their data requirements at a more abstract level and do not hard code details of how or where data is physically stored, fetched, and managed. Also, they do not perform low-level data manipulation. Siebel Janna Service Objects perform these tasks.

Siebel Janna Applications provide one Siebel Janna Service Object for each of the most commonly used tables in the Siebel Janna database. Because Siebel Janna Applications' open architecture allows for easy extensibility, it is common to have your own database schema integrated with the Siebel Janna database. The data in these extension tables need to be accessed and processed to supply the often complex data requirements of the custom presentation objects. Custom Siebel Janna Service Objects authored by the developer will manage the storage, retrieval, and processing of data from these extension tables.

NOTE:  Siebel Janna Service Objects need not only access data from a database. You can customize Siebel Janna Service Objects to enforce other business rules or manage or use other Siebel Janna Service Objects through aliasing.

Siebel Janna Application Server (SJAS)

SJAS provides a server-centric environment for developing and deploying three-tiered Siebel Janna Customer Relationship Management solutions based on COM. It is a key component of Siebel Janna Applications. With SJAS, Siebel Janna Service Objects run under the control of SJAS on servers and are invoked by presentation objects (through Requestors) running on clients through Microsoft's Distributed COM (DCOM) or Microsoft Message Queue Server (MSMQ) technologies, or MAPI. Clients can be a mixture of conventional applications and Active Server Page (ASP) scripts running within Microsoft Internet Information Server (IIS).

Siebel Janna Data Access Objects (SJDAOs)

Siebel Janna Data Access Objects (SJDAOs) are a layered hierarchy of COM objects used to manipulate Siebel Janna data. The SJDAO is comprised of two layers—the physical layer and the logical layer. Each object has one or more properties that define its characteristics and one or more methods that you use to perform various operations on the object.

The Physical Layer. This physical layer wraps the functionality of the ODBC API into a series of COM objects that physically connect and manipulate data in an ODBC database. The objects are maintained in the JDUODBC.dll library. If the database goes offline, the physical layer insulates the application from abnormal termination and reconnects to the database when it is online again.
The Logical Layer. The logical layer is the programming interface for the Siebel Janna Database Engine or the physical layer. Objects represent each table in the Siebel Janna database. Each object has a set of properties that define its characteristics and one or more methods that you use to perform various operations on the object.

Siebel Janna Data Objects

Siebel Janna Data Objects transport the state of business objects throughout the architecture. They represent the most basic component of the Siebel Janna architecture and typically encapsulate a single record in a table or view from a database.

The Data Layer

The data layer represents the myriad of data sources distributed across an enterprise system. These sources could be Siebel Janna databases or any other data sources. Data sources containing a Siebel Janna application database can be accessed through ODBC. Data on other data sources can be accessed using any industry data access technologies like ActiveX Data Objects.

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