Chapter 4 Legacy Systems Integration (Integration between the L.S. and the Web)

Introduction  The organization investment in legacy system is worth considering.  It may have spent a great deal of money and human resources developing the system that are now in place in the organization.

Definition the legacy systems Existing applications and systems within your organization that are not Web-based or integrated with yet the Web are referred to as legacy system. legacy system and applications may reflect the way the organization operated in the past, deserving the name legacy systems.

Definition the legacy systems A legacy system is an existing computer system or application program which continues to be used because the user does not want to replace or redesign it. Legacy systems are considered to be potentially problematic by many software engineers for several reasons. Legacy systems often run on obsolete (and usually slow) hardware, and sometimes spare parts for such computers become increasingly difficult to obtain.

Evaluating Legacy Systems The organization has many applications and systems in place, some of them work smoothly, others in need of upgrade or overhaul, when you are adding the Web to your arsenal of tools, you have the opportunity to reevaluate existing systems and applications and determine which ones should are worth retaining, which ones need to be upgrade, and which ones should be replaced.

Evaluating Legacy Systems  How you can determine which legacy systems are worth retaining ? consider the systems (hardware and operating system) that are in place and then survey the applications running on those systems. It may be worth retaining the systems and revamping or replacing the applications.  It is important to decide which systems and applications are basically performing their intended functions and are worth integrating into the Web and which level of integration is the most appropriate for each application.

The three basic levels of integration that may work with your legacy applications:- Frontend integration whereby a Web GUI (Graphical User Interface) fronted provides the presentation layer for the legacy application. Business logic integration whereby the business logic of the application is integrated with the web. Data access layer integration whereby the backend data access is integrated with the web.

Table 4.1 Inventory of legacy Applications for the A corporation Web Integration Retain, Upgrade, Replace ? PlatformFunction Applicatio n Frontend integration Retain-works fine but needs better interface Mainframe Keep track of each employee’s vacation Vacation Scheduler CORBA interface available, business services integration Upgrade –need to allow for customization of reports and accessibility by others and need to tie in with other accounting software UNIX work station Payroll processing for salaried and hourly employees as well as contractors Payroll Processor Replace with interactive self service java application that works on intranet, JDBC interface to backend databases Replace – proprietary application processing, manual updates PC Employee options on healt, dental, vision, and life insurance, dependent care accounting Benefits Already integrated with intranet Retain – New Web application built for intranet UNIX server Obtain market research materials from market research firms and from public sources Library

1) Fronted Integration Understand Integration Between A Web GUI fronted and A Legacy System Application. Determine Which Applications Should Be Integrated on the presentation layer Fronted integration provides the loosest form of coupling between a legacy application and the Web. The easiest way to integrate an application with the Web is to provide data entry facilities through a forms-based Web fronted. Web-based Interface GUI End User Legacy System

The limitations to Fronted Integration CGI (Common Gateway Interface) scripts increase network traffic since data is passed through to the legacy application directly. Increase in HTML via the browser

2) Business Services Integration There are a number of technologies that can be used to integrate your legacy application at this level 1- Integration With Remote Procedure Calls (RPCs). –RPC communication is limited to between client and server. –RPC is suitable for more fine grained jobs. –Programming will be much easier. Legacy System End User Internet Update Program

2- Common object request broker architecture ( CORBA )

Common object request broker architecture ( CORBA ) What is CORBA?What does it do? CORBA is the acronym for Common Object Request Broker Architecture, OMG's open, vendor-independent architecture and infrastructure that computer applications use to work together over networks. Using the standard protocol IIOP, a CORBA-based program from any vendor, on almost any computer, operating system, programming language, and network, can interoperate with a CORBA-based program from the same or another vendor, on almost any other computer, operating system, programming language, and network.

Common object request broker architecture ( CORBA ) What is CORBA good for? CORBA is useful in many situations. Because of the easy way that CORBA integrates machines from so many vendors, with sizes ranging from mainframes through minis and desktops to hand-helds and embedded systems, it is the middleware of choice for large (and even not-so-large) enterprises. One of its most important, as well most frequent, uses is in servers that must handle large number of clients, at high hit rates, with high reliability. CORBA works behind the scenes in the computer rooms of many of the world's largest websites; ones that you probably use every day. Specializations for scalability and fault-tolerance support these systems. But it's not used just for large applications; specialized versions of CORBA run real-time systems, and small embedded systems.

Common object request broker architecture ( CORBA ) How about a high-level technical overview? CORBA applications are composed of objects, individual units of running software that combine functionality and data, and that frequently (but not always) represent something in the real world. Typically, there are many instances of an object of a single type - for example, an e-commerce website would have many shopping cart object instances, all identical in functionality but differing in that each is assigned to a different customer, and contains data representing the merchandise that its particular customer has selected. For other types, there may be only one instance.

3) Data access layer integration Legacy System DB Web-based Interface GUI Internet End User

Common object request broker architecture ( CORBA ) Who is using CORBA already? Thousands of sites rely on CORBA for enterprise, internet, and other computing. The Object Management Group maintains an entire website devoted to user design wins and success stories. At last count, there were over 300 stories on the site.

Backend Integration Java Language Support. Java Database Connectivity ( JDBC ). JDBC Drivers There are four different types of JDBC drivers :- –The JDBC – ODBC Bridge. –A native –API partly Java Technology – based driver. –A net –protocol All Java Technology – based driver. –A native protocol All Java Technology based driver.

Legacy Applications Appreciate the ease of use gained from the marriage of a web GUI frontend to a legacy application. Decide if some of your legacy applications just need a new frontend to be more usable. Examples: –Registration and Admission. –E-Commerce.

End The Chapter Thank you for attention & good listening