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Understanding The BEA eLink System
This section discusses the following topics:
BEA eLink Solution Overview
BEA eLinkTM provides an open Enterprise Application Integration (EAI) solution that allows applications throughout organizations to communicate seamlessly. Using EAI, you gain the long-term flexibility and investment protection you need to keep up with today's ever-changing business environment.
Typically, companies use packaged applications to automate internal operations, such as financial, manufacturing, or human resources. While they successfully address the needs of these specific areas, these proprietary platforms often do not work together. To compete today, you need a much greater exchange of information. Systems need to communicate at a process level within your own organization, as well as with customer's and supplier's systems. BEA eLink Platform is the underlying basis of BEA eLink, a family of off-the-shelf enterprise application integration (EAI) products that leverage the BEA transaction platform to integrate existing legacy applications with customer-focused and business-to-business e-commerce initiatives.
BEA eLink Platform provides a proven infrastructure for integrating applications within the enterprise and across the Web. BEA eLink Platform ensures high-performance, secure transactions and transparent access to mission-critical applications and information throughout the enterprise and across the Web. Figure 1-1 illustrates the eLink logical architecture and shows where the eLink Adapters fit into the process.
Figure 1-1 BEA eLink Solution Illustration
The entire BEA eLink family (including all options and adapters) is highly scalable. Multiple instances of BEA eLink components can collaborate so that work is divided between eLink domains. BEA eLink includes Simple Network Management Protocol (SNMP) integration for enterprise management.
The current BEA eLink Platform leverages the BEA Tuxedo infrastructure because it is based on a service-oriented architecture. Both BEA Tuxedo and BEA eLink communicate directly with each other and with other applications through the use of services. Multiple services are grouped into "application servers" or "servers". The terms Tuxedo services/servers and eLink services/servers can be used interchangeably. Because this document is specifically addressing the eLink family, the terms "eLink service" and "eLink server" are used throughout.
The BEA eLink Platform complies with the Open Group's X/Open standards including support of the XA standard for two-phase commit processing, the X/Open ATMI API, and XPG standards for language internationalization. C, C++, COBOL, and Java are supported. The BEA eLink Platform connects to any RDBMS, OODBMS, file manager or queue manager, including a supplied XA-compliant queueing subsystem.
The following components operate with BEA eLink Platform:
BEA eLink Adapter Overview
eLink Adapters provide a communication path between the eLink Platform and third-party applications such as PeopleSoft or SAP. eLink Adapters are implemented as eLink Platform servers. Servers are software modules responsible for processing service requests made by requestors and potentially sending replies back to the originator of the request. Services are provided by code that accesses the business logic of a third-party application.
An eLink Adapter must accomplish at least two things. First, it must normalize the communication between the two components. Second, it should advertise business level services supported by the third-party application into the eLink Platform environment. In addition, application to eLink Adapters must publish events with associated data on behalf of the third-party application in the eLink Platform environment. If the third-party application allows scripting or other extensions, it should be capable of invoking known eLink Platform services advertised by other third-party applications.
An adapter may support both the eLink bound paths (application to eLink) and third-party application bound paths (eLink to application); however, it is recommended that an adapter be implemented for only one path. If both application to eLink and eLink to application paths are required, they should be implemented as two separate servers. Separate servers allow for a more flexible solution because the usage requirements of eLink-bound and application-bound adapters may vary widely.
eLink Adapters use FML32, a BEA native data structure, to communicate with other components in the integration environment. The third-party native interface is used to communicate with the third-party application. eLink Adapters act as a "translator" between the third-party API and the BEA ATMI. This translation is facilitated by use of the ADK API.
Figure 1-2 eLink Adapter Illustration
BEA eLink Adapter Development Kit Overview
The eLink Adapter Development Kit (ADK) is a set of tools and libraries that allow BEA, our partners, and our customers to build adapters that interact with the eLink Platform. The ADK helps programmers build adapters for third-party software without in-depth knowledge of the eLink Platform.
The ADK consists of:
BEA eLink Platform Architecture
The eLink Platform communications application programming interface, Application to Transaction Manager Interface (ATMI), is a collection of runtime services that can be called directly by a C (or COBOL) application. These runtime services provide support for communications, distributed transactions, and system management.
The Management Information Base (MIB) maintains a virtual repository of all the configuration and operational information for a runtime eLink environment. The eLink services are implemented using a shared bulletin board (BB) that contains configuration information. This is the dynamic part of the eLink. Servers advertise their services in the Bulletin Board. The Bulletin Board Liaison (BBL) is an administrative eLink server that is the keeper of the Bulletin Board. There is a BBL on every machine participating in the integration infrastructure; the BBL coordinates changes to the local copy of the MIB. The Distinguished Bulletin Board Liaison (DBBL) is responsible for propagating global changes to the MIB and is the keeper of the static part of the MIB. The MASTER node is the computer where the DBBL runs.
Administrators use an ASCII file to specify eLink system configuration. This file, called the UBBCONFIG file, is used as input by the configuration loading utility, tmloadcf. The tmloadcf utility generates a binary version of the configuration called the tuxconfig file. This binary file is used by the system to construct the Bulletin Board and contains the persistent part of the MIB.
Servers are processes that provide one or more services. They continually check their message queue for service requests and dispatch them to the appropriate third-party application. A service is the name of a server interface. Many servers can support a single service, thereby providing for load balancing and a fail-safe mechanism. The mapping of services to servers is recorded in the Bulletin Board. When a service request is made, the Bulletin Board forwards the request to a server (eLink Adapter) that advertises that service. An eLink server advertises a service by posting its name in the Bulletin Board.
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