To some, one thing could be different form another, to someone else. They precisely have different set of requirements which help them to conceptualize what they think is true.
The point when emergency changes have to be made to systems they can be modified in the requirements document using a suitable process model. The model to be employed is the spiral model. The process activities involved in maintaining the consistency between the requirements document and the system implementation are:
The spiral model is best to be used as it keeps on circling and thereby steps in all the phases of software development life cycle including system implementation and requirements documentation gets implemented. It makes the system consistent by circling every time a change takes place in the software and traveling all the phases so as to make it organized and complete. It is the best model to accommodate the changes in the business environment and document it for future reference.