Tap the wells of legacy data using the DataFlex WebApp Server

Legacy Applications  Procedural code.  Hundreds of programs in application.  Years to write, debug and test.  Stable and reliable.  Users are well trained.  Difficult to leave - Modified FMAC or DFRun.  Years of data entry means big data files.  WebApp Server can add tremendous value to this data.  Reports on the web.  Data entry / remote access via the web.  Data mining.

Environments  The great news is that DataFlex data (2.3 and higher) is readily available for the web, regardless of the deployment platform.  We do not need to port the application to the NT server.  Legacy application / data can reside on Novell, or UNIX servers.  Client Server back-ends on UNIX will connect using protocol of Server engine.  For native DF data, UNIX Connectivity products mount the UNIX file system as a NT drive.  SAMBA  NFS  SCO / VisionFS  FacetWin  Remember opportunistic locking and readcaching always apply.  If UNIX / Share locking mechanisms are in sync, then data integrity is preserved.  How can we test if the lock managers respect each other?

FacetWin Connectivity  WebApp Server is multi-threaded when processing many web requests.  FacetWin bases user counting per connection, not processes, so a 1 user count license is all that is necessary for the WebApp Server.  FacetCorp offers technical support to their customers. Data UNIX running connectivity daemon NT4 / IIS WebApp Server 1user

Keeping The Status Quo  If we have a well programmed application that earns our reputation, we may be hesitant to change the system.  If we have invested a lot time or money in a system and we are unable to or unwilling to go through it again.  If we don’t want to re-train our users nor rewrite training manuals.  If we want to continue to use our legacy technology in its full capacity without modifying a line of code and have it work with latest Internet technologies. Then the DataFlex WebApp Server is the way to go!

Benefits For Legacy DF Programmers  No longer trapped in legacy technology by a legacy system.  Learning object-oriented programming is accelerated without having to master UI sub-system messages.  Implementing business rules with the DBB makes it easier to learn and understand event programming.  Solution for remote access - Client / Server architecture.  Reuse business rules regardless of database engines without re-writing server side stored procedures.  Staying current with DF technology will ensure your application is current with today’s DF technology and tomorrow's, as DataFlex evolves into the next millenium.  HTML characteristics are similar to procedural DataFlex without image limitations.  Ahead of the game because we know our customers, market and business rules.  Get the same RAD development for the web as we expect from DataFlex tools.

Are Data Dictionaries Required?  Typically reporting would be the first step.  Report can be written with standard DataFlex looping control.  Repeat / Until  While / Found  For_all loop  Even a report macro worked in the WBPO.  Data entry applications should use Data Dictionaries for the easiest enforcement of business rules in a multi-user environment.

The Easiest Way: Data Dictionaries  Take advantage of the workspace concept.  Separate old development from new development.  Prevents developing against live files.  Start with a bare bones Data Dictionary automatically generated by the DBB.  Business rules need not be complete, add as needed for web page.  DDOs are the most manageable to develop and maintain business rules.  No more searching through thousands and thousands of lines of code.  DDO ensure data integrity between WAN and LAN.

Creating Data Dictionaries  Different runtimes enforce relationships differently.  WebApp / VDF runtime will check: relating field is same size and type.  Uniquely indexed parent, child relates to parent, n : 1 is still the same.  Look for and remove multiple relationships between two files.  Start by analyzing relationships first to harness the DF methodology, rather than fighting hundreds and hundreds of messages.  Just because every file can be related, to another file does not mean they need to be. - I usually need to remove relationships during upgrade to VDF.  Use relationships for finding parents and constraining children.  How To Check relationships:  DDB > Reports > Check Relationships and draw tree by hand.  VDF Database Structure Viewer by Hans van de Laar

Relationship Tree  Diagram generated by: VDF Database Structure Viewer, authored by Hans van de Laar

CIRCULAR OR DIAMOND? A BC D

Trend In Internet growth?  For DF data, the WebApp Server is the fastest way in the word to get data on the web.  If you don’t “ride the wave soon” you will miss out on a great opportunity.  Gordon Bell Senior Researcher Microsoft Research points out expected Internet growth.

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