ASPA, Maryland Chapter WorkshopOvercoming Challenges to Implementing e-Government

OvercomingLegacy System Challenges

———— Don’t Let the BestDrive Out the Good

Thomas A. Darling, Ph.D.Dept. of Public Administration, &Schaefer Center for Public Policy

University of Baltimore(410) 837-6195

tdarling@ubmail.ubalt.edu

February 5, 2001

The Legacy System ChallengeGetting Info From Here To There

Legacy System: Generally a host/mainframe system ANDall the DATABASES and applications it runs.

Any system that was implemented to meet older business requirements.

Replicated Information

“Close-Enough” to Real-Time

Legacy (Batch) Interfaces

Cracking the Legacy System NutAccept Three Key Compromises

Information Flow RequirementsA Simple Typology

Outbound: From You to Them Aggregate government information

Census or health care statistics Individual-level government records

Accident reports or real estate records

Inbound: From Them to You Filings and requests

Filing state taxes Ordering birth, death, and marriage

certificates

Exchange: The “Interaction Transaction” The “incomplete” transaction

Renewing driver’s license/registration The complete transaction

State park camping reservations

Massage

ReplicatedInformation

Data Server/Web Server

LegacySystem

LegacyInterface

IntermediateFile

Batch Process on Legacy System “When Possible”

Outbound: Aggregate InformationCensus Data or Health Care Statistics

Aggregate Data Design It’s a Data Warehouse

Design your information system Analytical databases are different than day-to-day,

operational (transactional) databases. Analytical databases do not naturally “fall out” from

the detail database. Recognize, and design for, complexity.

Decide what questions you will answer

Pick a manageable number of questions, variables, and aggregation levels

Account for time-related effects

How will variables “over time” be handled?

Massage

ReplicatedInformation

Data Server/Web Server

LegacySystem

LegacyInterface

IntermediateFile

Batch Process on Legacy System “When Possible”

Outbound: Individual RecordsAccident reports or real estate records

Massage

Data Server/Web Server

LegacySystem

LegacyInterface

ApplicationInterface

File

Inbound Legacy Batch Process “When Convenient”

Inbound: Individual RecordsTax Filings or Certificate Orders

Application Interface File: Bad News Legacy In-bound is Harder than Out-bound

Because outbound data is drawn from the legacy system’s production database, it already has met all of the organization’s business rules

– the checks and balances required of production data.

Inbound information, however, must be “scrubbed” before it can be allowed into

the production database. Not only must itundergo routine data-entry checks, it alsomust be checked for conformance with the

organization’s business rules.

Although not an issue with the current examples, such conformance checks usually require

real-time access to the production database.

Constructing the Legacy InterfaceGood News: Flexible and Re-Usable Routines

Assumption: I assume there already existsa method to get inbound information into

the production database – probably, a terminal-based data entry screen.

The legacy interface should be designedto “push” the inbound data into the legacy

systemat the same place (and in the same format)

as the existing data entry system.

Doing this provides extra benefits –inbound information from any source(including a newly-created, PC-based

data entry system) can be pushed intothe system through the same access point.

Data Server/Web ServerLegacy

System

Legacy InterfaceIncluding

Conformance Checks

ApplicationInterface

File

Exchange: “Incomplete” TransactionsRenewals (Driver’s License or Registration)Replicated

InformationLegacy

Interface

IntermediateFile

Massage

Massage

Accept

Reject

Data Server/Web Server

LegacySystem

Legacy InterfaceIncluding

Conformance Checks

ApplicationInterface

File

Exchange: “Complete” TransactionsCamping Reservations Replicated

InformationLegacy

Interface

IntermediateFile

Massage

Massage

Accept

Reject