Verifying Use Cases, Data Flow Diagrams, Entity Relationship Diagrams, and State Diagrams via State Linkages The purpose of this brief article is to provide a simple example on how to link and verify four models: use case, data flow diagrams, entity relationship diagrams, and state diagrams. Note the word verify, not validate. Verify in this context means that the technique is consistent and complete, not that it reflects correct requirements. In writing this article, the author assumes the reader understands the four models mentioned above. With this understanding, the article focuses on the relationship between the models via states. Use case is an alternative technique for documenting functional requirements for interactive operational systems. It models a dialogue (a process) between a user (actor) and a user goal (use case). The technique consists of a diagram and a description. The description of a use case includes pre and post conditions. The precondition is the st...
Waterfall methodology is a software development methodology that is based on sequential-linear approach of software development. It reinforces the notion of "define before design" and "design before code". Whereas agile is based on increamental-iterative approach where requirements are expected to change frequently. # Waterfall Agile 1. Waterfall methodology is sequential and linear. Agile methodology is increamental and iterative. 2. Requirements have to be freezed at the beginning of SDLC. Requirements are expected to change and changes are incorporated at any point. 3. Working model of software is delivered at the later phases of SDLC. Working model is delivered during initial phases and successive iteration of the model are delivered to the client for feedback. 4. It is difficult to scale-up projects based on waterfall methodology. Scaling up of products is easy because of the iterative approach. 5. Customers or end user doesn't have a...