4.3 Understand Requirements

Once the stakeholders have been identified, expectations for the modernization effort must be established and requirements, as well as nonrequirements, agreed on among the stakeholders. Creating a steering committee or a working group consisting of stakeholders helps to identify win-win situations that will guide task definition and prioritization.

Requirements

User , system, and nonfunctional requirements can come from the legacy system, business process reengineering, stakeholders, and technology advances.

Legacy System

Most requirements in a modernization effort are derived from the legacy system itself, given that the decision to modernize acknowledges the existence of business rules and knowledge that must be preserved. To a large extent, the legacy system has fixed normative requirements. Thus, the modernization effort is typically geared toward improving system qualities, such as maintainability, ease of use, or performance. The risk of deriving requirements from the legacy system is that it may result in the recodification of obsolete or inefficient business practices.

Business Process Reengineering

New requirements may also stem from business process reengineering (BPR). BPR attempts to realign the existing business processes with current needs to produce efficiencies. Business processes are codified in existing information systems, so it makes sense to perform BPR before beginning a legacy system modernization effort, to avoid recodifying obsolete or inefficient processes. This does not have to be a full BPR process. BPR raises the stakes in a legacy system modernization effort because business processes need to be reevaluated, revalidated, and revisited before any modernization work can begin. Required changes to legacy systems resulting from BPR can also affect multiple systems in an organization, making the effort difficult to scope.

Stakeholders

Stakeholders generate new requirements, based on years of interaction with the legacy system. These requirements are often recorded in outstanding change requests . Many of these requirements are valid, but others may simply be user infatuations or have been made obsolete by technology. For example, a requirement to add hot keys to a menu-based system might be made obsolete by a decision to use a graphical user interface.

Technology Advances

Stakeholders often want to include technical advances as requirements. The stakeholders may believe that advances in technology can address such problems as unacceptable performance, poor maintainability, or poor usability. Although this often is the case, new technologies can also bring new, unanticipated problems.

Constraints

Constraints are decisions that have already been made and therefore place restrictions on the as-desired system or development processes. These constraints can be managerial , such as a predefined budget or schedule; architectural, such as a predefined corporatewide architecture; interface related, such as conformance to a specific standard or API; or process related , such as using an incremental development and deployment process.