A use case is a sequence of interactions that will develop between a system and its actors in response to an event initiated by a main actor on the system itself. The use case diagrams serve to specify the communication and behaviour of a system through its interaction with users or other systems. A figure that shows the connection between the actors and the use cases in a system is the same. A relationship is a connection between the elements of the model, for example, specialization and generalization are relationships. The use case diagrams are used to show the system requirements by showing how it reacts to events that occur in or within its scope. The use cases are basically used in the System Modelling Process, based on a perception or perspective that the object-oriented paradigm poses, and in this case the object-oriented analysis and design.

They are part of the Unified Modelling Language (UML), which in turn is made up of many other tools. Basically diagrams such as: Class Diagrams, Sequence Diagrams, Collaboration, State Transition, State Diagrams Activity, Components, Deployment, among others. All of these are used throughout the stages or life cycle of the development process. The main application of the use cases is in the analysis and design process but particularly in the definition of user requirements. It is an excellent communication tool due to the simplicity of its elaboration as well as its understanding.

User stories: User stories are descriptions, always very short and schematic, that summarize the specific need of a user when using a product or service, as well as the solution that satisfies it.  Like many other agile tools, user stories emerged as a response oriented to the software development sector, although over time they are being applied to other types of business. Its main function is to identify supposed problems, propose solutions and estimate the effort required to implement the proposed ideas. User stories are an instrument for raising requirements for software development. It is emerged with the emergence of new agile development frameworks, such as Scrum or the different techniques that comprise Extreme Programming (XP).

Similarities between use cases and user stories

The use cases and user stories are similar because both are ways of organizing requirements. They are different in that they arrange the requirements for different reasons. Use cases organize the need to form a story that shows how users relate to and use the system. Therefore, it focuses on the user’s purpose and how the interface with the system meets the goals. Instead, ANXP stories (and often referred to as functions) divide requirements into parts (parts, fragments) for planning purposes. Stories are explicitly divided until they are estimated as part of the XP version planning process.

They have a compound relationship. Stories are generally big /tiny because they must be fully developed (built) in iteration (one or two weeks in XP). Small use cases may be match to stories. Still, a story can be one or more situations in a use case (remember the situation). What are the other alternatives that everything will be fine, where? One where everything goes well and other alternatives, where things may not work out well), or one or more steps in a use case. A story may not even have to be shown in the use case narrative, for example adding a new method of depreciating resources to a pop-up list.

Do you need both? As in many things, in theory yes but in practice no. SoftTeco teams could use the use cases at first to build a narrative (general) image, and then for planning, they divide them into stories. Other teams go straight to the stories. Others could only make use cases and write down their text to show when each feature is developed.