This article presents an overview of the Software Development Life Cycle(SDLC), alternate lifecycle models, and associated references.
THE SDLC WATERFALL
Small to medium database software projects are generally broken down into six stages:
When a prototype is generated, the developer produces the minimum amount of code necessary to clarify the requirements or design elements under consideration. No effort is made to comply with coding standards, provide robust error management, or integrate with other database tables or modules. As a result, it is generally more expensive to retrofit a prototype with the necessary elements to produce a production module then it is to develop the module from scratch using the final system design document.
For these reasons, prototypes are never intended for business use, and are generally crippled in one way or another to prevent them from being mistakenly used as production modules by end-users
The PER and PDR may, at their discretion, allow the development effort to continue while previous stage deliverables are updated in cases where the impacts are minimal and strictly limited in scope. In this case, the changes must be carefully tracked to make sure all their impacts are appropriately handled.
The theory is that the set of requirements is hierarchical in nature, with additional functionality building on the first efforts. This is a sound practice for systems where the entire problem is well defined from the start, such as modeling and simulating software. Business-oriented database projects do not enjoy this advantage. Most of the functions in a database solution are essentially independent of one another, although they may make use of common data. As a result, the prototype suffers from the same flaws as the prototyping lifecycle described below. For this reason, the software development team has decided
against the use of the spiral lifecycle for database projects.
The theory is that end users can produce better feedback when examining a live system, as opposed to working strictly with documentation. RAD-based development cycles have resulted in a lower level of rejection when the application is placed into production, but this success most often comes at the expense of a dramatic overruns in project costs and schedule. The RAD approach was made possible with significant advances in software development environments to allow rapid generation and change of screens and other user interface features. The end user is allowed to work with the screens online, as if in a production environment. This leaves little to the imagination, and a significant number of errors are caught using this process.
The down side to RAD is the propensity of the end user to force scope creep into the development effort. Since it seems so easy for the developer to produce the basic screen, it must be just as easy to add a widget or two. In most RAD lifecycle
failures, the end users and developers were caught in an unending cycle of enhancements, with the users asking for more and more and the developers trying to satisfy them. The participants lost sight of the goal of producing a basic, useful system in favor of the siren song of glittering perfection.
• ANSI/IEEE 1028: Standard for Software Reviews and Audits
• ANSI/IEEE 1058.1: Standard for Software Project Management Plans
• ANSI/IEEE 1074: Standard for Software Lifecycle Processes
• SEI/CMM: Software Project Planning Key Process Area