applications

Success for PAYE by BILL HOPKINS

D uring the past decade, failures land misadventures of large on-

line system projects, particuiar- ly in the public sector, have been the subject of major articles in the com-

mercial and computer press. It is

heartening, therefore, that during the first half of the 1980s there is a real

success story - the Computerization of the UK’s inland revenue taxation

system, Pay As You Earn, (COP).

In October 1983, the COP system commenced live operations, on sche- dule and within budget, in 14 pilot

districts in the West Midlands. When fully implemented in 1987, there will

be 12 regional processing centres across the country, providing about 600 tax offices with online update and

retrieval facilities via some 18000 visual display terminals. 27 million

taxpayer records and over one million

employer records will be brought on to the computers.

The processing centres, using ICL mainframe configurations, will be

linked together by an integrated data communications network. The pilot

Abstract: Computerization ofthe L’K’s tax system (PA YE) is ?ZDZL’ in operation in 14 West Midla?lds pilot districts. The key factors

in the success of this major development include a rigorous development methodology, stnngent controls, and an effective relationship between the Inland Revenue, the contractors and the consultancy groups.

Keywords: system d~e~opment, project management, user involvement.

Bill Hopkins was technical manager throughout the design, development and testing stages of the COP project.

El

LIVINGSTON

AT KILBRIDE

NETHERtON-\ Ltr /I’

- LLANtSHEN ‘-A& / _,/-

TERBOROUGH

COP REGIONAL PROCESSING CENTRE

NETWORK PLAN

Figure 1. The pilot scheme will be copied in 12 UK processing centres,

system provides the basic applications software suite which, after successful

evaluation, will be replicated through-

out the 12 UK processing centres.

The COP system was developed during the past two years at the National Development Centre in Tel- ford, Shropshire by a joint Inland

Revenue, ICL and Computer Scien- ces Company (CSC) team of 180 personnel. The effective integration of skilled and experienced technical

consultants and DP trained civil ser-

vants with knowledge of the tax system was a significant factor in the

successful completion of the project.

CSC, was charged with the respon- sibility for technical management of the project. Its staff filled key tech-

nical line management positions and in addition to technical direction and support were required to effect trans- fer of knowledge so that technical management roles would revert to

~0126 no 5 june 1984 0011-684X/84/050031-03$03.00 0 1984 Butterworth & Co (Publishers) Ltd. 31

Revenue staff prior to system replica- tion. This objective has been fulfilled. CSC continues to assist the Revenue in advisory and technical support roles. There is no doubt that utiliza- tion of a consultancy firm in this manner has been a demonstrably effective approach to the development of a large system.

One objective of the COP project was the provision of greater ~exibility for dealing with future changes, either within the PAYE system or in a more far-reaching reform of personal taxa- tion. In order to achieve this objec- tive, an overriding requirement of flexibility and maintainability was im- posed on the system design.

There are four other factors which influenced the approach to design and development, and associated controls:

The need to train, from scratch, the Inland Revenue programmers who were to code the system. The need to implement some eight to ten system software upgrades (across VME!B, TPMS, IDMS, DDS and NPOS) over the period from award of contract to the start of COP system replication. The need to develop a substantial amount of ‘middleware’ to provide capabilities which were not inhe- rent in the system software. The need to progress a number of other project activities in parallel in order to meet the ‘live operations’ target of October 1983, viz:

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- - -

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procurement and demonstra- tions system software validation development centre installation processing centre planning and implementation software ‘builds’ development and integration user procedures

Given these constraints, the COP system was developed within the framework of Computer Sciences’ Digital Systems Development Metho-

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dology (DSDM). DSDM is a syn- thesis of proven management and development practices which encom- pass the entire system life cycle. It specifies the management, develop- ment, organization and control com- ponents and approaches necessary for successful large-scale ADP projects. At the same time, it provides the flexibility for choosing those specific tools and techniques which are best suited to the client and system envi- ronments .

Major features of the system development

The major features of the COP system development are summarized as follows:

Vulidati~ and v~~cati~n techni- ques providing a mechanism for vali- dating the user’s requirements, veri- fying the design against the require- ments and establishing a one-to-one mapping of functions across require- ments, design and testing. This was achieved through the use of CSC’s System Verification Diagrams (SVD) technique combined with highly structured review processes.

St~tured design methad~~o~ which imposed stringent design/develop- ment standards, and comprehensive and disciplined review processes. This was achieved by the adaptation of Yourdon structured design techni- ques and the establishment of a re- view and quality control mechanism which ensured the accuracy and qual- ity of all software products and associ- ated documentation.

Automated data dict~ona~ system. establishing complete control over data was one of the project’s first priorities. From the outset, the ICL data dictionary system was used to ensure that all data definitions were properly authorized and controlled and that naming standards were strictly adhered to. From this initial position, the influence of the diction- ary increased rapidly to a point where

it became a major factor in the control of the design and development effort.

Highly structured and modular approach to system design. Within the online and batch subsystems, func- tions (transactions) were decomposed (top down) into processes (elements) and modules. The 105 functional elements comprised 14 000 modules each of which represented about 15 20 lines of source code.

The whole software architecture of elements, compilation units and mo- dules was defined and controlled in a strict manner by the data dictionary. This highly modular design technique along with the Yourdon functional decomposition process enabled the logical and straightforward produc- tion of program (module) specifica- tions (in structured English format) which were easy to code, verify and test, and which resulted in standard- ized and consistent computer code throughout the system.

The restrictions imposed on pro- gramming structures precluded any variation in programming style be- tween individuals or between deve- lopment teams. This has been a major factor in the successful utilization of initially inexperienced programmers.

Build approach. The system was constructed in a series of Builds according to a Build plan. It is this plan which dictated the order in which software elements were pro- duced. Each Build provided a set of functional capabilities which were demonstrated to the user. When a Build stage was reached, the preced- ing Builds were integrated and tested regressively, culminating in a full scale test on completion of the final Build. An im~rtant aspect of the Build approach was that it provided early visibility of the developing sys- tem to both the user and technical management.

Following each Build, the system was run and measured against theore- tical sizings by the Pactel-led OR team to ensure that the developing system remained within the original perfor-

data processing

applications

Figure 2. The Build plan dictated the order in which software elements were produced.

mance criteria. in support of impact analysis and replanning exercises. In summary,

configuration management provided the single point of system ownership

and control.

Sophisticated and fully automated test environment. The COP system test

environment comprises ICL test tools

(path analysis, terminal simulators, etc.) and project developed testing software. Almost all test scripts and

data were automated and reusable in expanded or modified form. System test environments could be establish-

ed (automatically and very quickly) to

perform regression testing on COP

ICL system software and new applica- tion Builds. The effect of any change could be tested regressively through-

out the whole system within a single day.

Rigorous management control. The design, development, testing and im- plementation of all system compo-

nents (configuration items) were con-

trolled by a configuration manage- ment section. Change control, soft- ware handover (from development to

testing) and software installation pro-

cesses were established to ensure that the impact of all proposed changes were assessed fully and that such changes were developed, tested and implemented in a controlled manner. The statistics gathering and status accounting functions of configuration management provided valuable data

~0126 no 5 june 1984

Maximum user involvement. The

preparation of the system requirement specification was a joint user and system designer effort. The system

was developed in several phases (Builds) and at the completion of each

Build, operational functions were

demonstrated and terminal access was

provided to the user to assist him/her in preparing his/her clerical proce-

dures. The user reviewed all system test scripts and was invited to modify and/or expand the scripts. With such

involvement, there were no surprises during the formal User Acceptance

Test (UAT) which was conducted over a three month period by real end

users from tax offices. Effective project control system. The

COP automated project control sys-

tem (Artemis) registered, monitored, and reported on the total network of several thousand project activities. The system provided total visibility, across all management levels, into the status of the project and was used on a continuous basis to assess the impact in terms of time and resources of

additional activities and replanning

requirements.

Results

All milestones associated with the

development and implementation of

the basic COP system in the West Midlands pilot region were met on

schedule. The system went live in

October 1983 with the commence-

ment of employer and taxpayer set- ting up activities which were com-

pleted three weeks ahead of schedule. The system is now undergoing a

comprehensive evaluation (technical, administrative, clerical) prior to the

decision to replicate nationwide.

Flexibility and control have been

amply demonstrated in that, during

development, a number of changes resulting from legislation were incor-

porated into the system. Up to com-

pletion of user acceptance testing some 500 changes to the user require-

ment were accommodated without schedule slippage. No major applica-

tion system problems have been en- countered since going live and average

availability of the system, since October 1983, has been 99.2%.

The way ahead

The joint activities of the project,

involving Regional Liaison, Training, Plessey, ICL, British Telecom and

PSA remain on schedule and there is every confidence in having the 12

Regional Processing Centres up and running by the end of 1987. By that

time it is planned to have a national tracing system operational using the

ICL Contents Addressable File Store system (a pilot system is currently

under development). Plans are also in

place to move to ICL’s multiprocess-

ing systems (super-dual 2988 and Estriel), and to use ICL’s Information Processing Architecture (IPA) as these products become fully validated and supported. 0

Inland Revenue, National Development Centre, Boyd House, Lawn Central, Telford Shropshire TF3 4HQ, UK. Tel: (0952) 502818.

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