Software migration projects are often bound either by time or cost or by both. If the project is bound by both time and cost, the user must sacrifice something else, usually the quality. The migration strategy depends on how the project is bound. Most migration projects are bound by time. The new system must be in operation by a given date, no matter what it costs. The project described here—a state employee payroll system—is bound by cost. It must remain within the budget, no matter how long it takes. The original costs were estimated based on the code size and the productivity measured in previous migration projects using three different approaches: conversion, redevelopment, and reimplementation. The conversion approach would have been the cheapest, but it had already been tried and failed. The redevelopment approach was considered to be out of the question due to the high costs. Thus, reimplementation remained as the only alternative. The costs of this approach were estimated using three different estimation methods and approved by the state government. The project has been in progress for 4 years, and until now, the estimated costs and actual costs are in the same order of magnitude: the costs have remained within budget. In fact, the costs are less than what was estimated with some methods. As this particular project is not bound by time, it is a good example of continuous migration.

中文翻译：

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成本驱动的软件迁移：一份经验报告

软件迁移项目通常受时间或成本的约束，或受两者的约束。如果项目受时间和成本的约束，用户必须牺牲其他东西，通常是质量。迁移策略取决于项目的绑定方式。大多数迁移项目都受时间限制。无论成本如何，新系统都必须在给定日期前投入使用。这里描述的项目——一个州雇员工资系统——受成本的约束。无论需要多长时间，它都必须保持在预算范围内。原始成本是根据代码大小和先前迁移项目中使用三种不同方法测量的生产力估算的：转换、重新开发和重新实现。转换方法本来是最便宜的，但它已经尝试过并且失败了。由于成本高昂，重建方法被认为是不可能的。因此，重新实现仍然是唯一的选择。这种方法的成本是使用三种不同的估算方法估算的，并得到了州政府的批准。该项目已经进行了4年，直到现在，估计成本和实际成本处于同一数量级：成本保持在预算范围内。事实上，成本低于某些方法估计的成本。由于这个特定项目不受时间限制，因此它是持续迁移的一个很好的例子。该项目已经进行了4年，直到现在，估计成本和实际成本处于同一数量级：成本保持在预算范围内。事实上，成本低于某些方法估计的成本。由于这个特定项目不受时间限制，因此它是持续迁移的一个很好的例子。该项目已经进行了4年，直到现在，估计成本和实际成本处于同一数量级：成本保持在预算范围内。事实上，成本低于某些方法估计的成本。由于这个特定项目不受时间限制，因此它是持续迁移的一个很好的例子。