Post on 04-Jan-2016
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