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© 2003 Pluta Brothers Design, Inc. http://www.plutabrothers.com

Guest speaker:Joe Pluta, Pluta Brothers Design Inc.


This is a review of the various technologies for Web-enabling legacy applications. Companies Web-enable for many different reasons, and there are many different options. Some of them you may not have even considered. So, rather than rehash just the most popular techniques, this presentation will attempt to address all of your Web-enabling options. I’ll also try to give you some idea of the available products.


The Options

Replacing

Refacing

Rewriting


Replacing

If your existing system is out of date and unable to cope with your requirements, you may want to consider replacing it.

Many vendors can supply you with ready-made Web-enabled systems.


Refacing

Traditional Model

Terminal Emulation

Thin-Client Computing

Screen Scraping


Traditional Model

RPG Program

Display File

5250 Terminal

5250 datastream

Workstation Data

ManagementEXFMT


Terminal Emulation

RPG Program

Workstation Data

Management

5250 Emulator

Display File

EXFMT5250 datastream


Terminal Emulation

Many vendorsClient Access ExpressMochasoftRumbaShareware and Freeware 5250 Emulators


Terminal Emulation

Can now be done over VPNVirtual Private NetworkSecure, Stable, ReliableSpeed depends on Internet connection


Thin Client Computing

RPG Program

Workstation Data

Management

5250 Emulator

Display File


Thin Client

TCP/IPThin-Client Terminal

Server


Thin-Client Computing

Citrix MetaFrameGraphOn WinBridgeMicrosoft Terminal ServerSCO TarantellaVirtual Network ComputingWyse Winterm


Screen Scrapers

RPG Program

Workstation Data

Management

Screen Scraper Client

Display File



Screen Scrapers

Providers dwindling:Core TechnologyJacadaSeagullZephyr

Gone:EaselFlashpointMozart


To Scrape or not to scrape

Pros:No source changesDesktop integration

Cons:Fewer vendorsThe interactive tax


CFINT: The Interactive Tax

CFINT is a system job that consumes CPU resources when it recognizes that your interactive workload exceeds the interactive CPW rating of your machine. This governor is indiscriminate: When CFINT kicks in, all of your jobs, batch and interactive, come nearly to a standstill.


CFINT: The Interactive Tax

Most new iSeries models now offer only two options for interactive CPW:

Standard models have zero interactive capability

Advanced edition servers have full interactive capabilities

Except for the very smallest iSeries model, there is no middle ground.


How Much Does CFINT Cost?

To determine the direct cost of interactive CPW, go to the following IBM Web page:

http://www.iseries.ibm.com/servlet/factFind

This page compares the costs of various iSeries configurations.


How Much Does CFINT Cost?

The 810-0869 is a 2700 CPW machine. With zero interactive this model costs $50,000, while the same machine with max interactive costs $245,000 – nearly five times the cost.

CFINT makes your hardware costs higher.


IBM Options

Screen ScrapersHost PublisherHost On-DemandHATS

Like all screen scrapers, the IBM screen scraper solutions require interactive CPW.


IBM Options

RPG Program

Workstation Data

Management

Display File

EXFMT

Java Beans and Java

ServerPages

Browser

HTML

WebFacing Runtime (WAS)

Data Buffers


IBM Options

Until just recently, WebFacing also used interactive resources. Now, however, on the newer server models WebFacing will not require interactive CPW.


Interactive Technologies

Except for the new WebFacing offering, these are all interactive techniques that require no modifications to the legacy systems. These have an initial cost/benefit advantage. However, the new IBM pricing model has made interactive solutions too expensive for many businesses to maintain.


Rewriting


Rewriting

Two architectures:Client/Server

Application logic on client, makes requests to servers on the hostExamples: ODBC or Web services

Server/ClientApplication logic on server, makes requests to client to present dataExamples: X-Windows or good old 5250


Client/Server

Business logic encapsulated in servers or replaced by ODBC callsApplication logic moves to clientThree client options:

Remote databaseThick clientBrowser-based


Remote Database

AS/400DB2

ODBC Support

Workstation

ODBC based appli-cation


Remote Database

Remote database designs are relatively less flexible than other architectures. Because the client must have complete knowledge of the database layout, changes to business rules that affect your database can be difficult to deploy.

Remote database is best suited for ad hoc user queries, and not for mission-critical enterprise applications.


Thick Client

AS/400Program

Call Support

Workstation

Client/Server Appli-cation

Server

Server

Server


Browser Based

AS/400 Workstation

Web browser

Web Application

Serverxxxx

xxxx

xxxx

Note: This interface uses only HTML, so no sophisticated graphics are supported.

Server

Server

Server

Application and

business logic


Other

The other client/server architectures share the same concept: business logic is encapsulated in servers. Whether exposed via program call or Web service, or encapsulated in Java classes, these server programs are probably the ultimate goal of a complete rewrite.


Other

Unfortunately, there are no tools today that can directly mine business logic, although some companies are beginning to claim that ability. Certain 4GL vendors also claim to be able to encapsulate your business rules. But in most cases, a true client/server design will require a significant investment in rewrite (which also means re-testing).


Server/Client

Application logic unchangedI/O requests replaced by API callsThree UI options:

Thick client on workstationThick client appletCGI or servlet/JSP to browser


Browser Technologies

Static Web pagesCommon Gateway InterfaceServletsJavaServer PagesJSP and servlets


Static HTML

Workstation AS/400

Web Server

Web Browser

HTTP Request

HTML Data

Static HTML Pages


Workstation AS/400

Web Server

Web Browser

HTTP Request

CGI Program(RPG, Perl, …)HTML

Data Database Data

Common Gateway Interface


Workstation AS/400

Web Server

Web Browser

HTTP Request

Servlet(Java)HTML

Data Database Data

Servlet


Workstation AS/400

Web Server

Web Browser

HTTP Request

JSP ProcessorHTML Data

Database Data

JavaServer Pages JavaBeans

JavaServer Pages


Workstation AS/400

Web Server

Web Browser

HTTP Request

Servlet

HTML Data

Database Data

JavaServer Pages

JSP Processor

JavaBeans

Servlet/JSP


Server/Client

Application logic unchangedI/O requests replaced by API callsThree UI options:

Thick client on workstationThick client appletCGI or servlet/JSP to browser


Server/Client - CGI

AS/400 Workstation

Web browser

HTTP Server

Application rewritten to

replace workstation I/O with CGI calls.

xxxx

xxxx

xxxx



Server/Client - CGI

Replace I/O with CGI callsRequires an HTTP serverSeveral vendors

FreeStyle/400LegacyWebRelational Web (*)


Server/Client - Thick Client

AS/400Application

ClientServer Client APIs

Workstation

Thick Client

UI Server


Server/Client – Thick Client

Replace I/O with server/client APIMay require additional software

JacadaPSC/400Seagull


Server/Client - Applet

AS/400Application


Workstation

Web browser

HTTP Server

UI Server Applet


Server/Client - Servlet/JSP

AS/400Application


Workstation

Web browser

Web Appl. Server

Servlet

Java Server Page

xxxx

xxxx

xxxx



Server/Client – Servlet/JSP

Replace I/O with server/client APIRequires Web Application ServerMay require additional software

JacadaJaci/400PSC/400Seagull


Dialup Batch Thick Client Browser No Source Time CostEmulation Y N N N Y - -Thin Client N N N (N) Y + ++Scrapers (N) N Y N Y ++ +++WebFacing (N) (Y) N Y (N) ++ -C/S Y Y Y Y N ++++ -S/C CGI Y Y N Y N +++ +S/C thick Y Y Y N (N) +++ ++S/C browser Y Y N Y (N) + +++

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client options

client terminal server

interactive solutions

interactive technologies

interactive resources

interactive techniques

interactive capabilities

interactive workload