Use Case Diagram In Nutshell for the Business Analyst

Use case - consists of a few sentences summarizing the use of the case, which can easily be placed in a spreadsheet cell, while the other columns in the spreadsheet priority, duration, an expensive method of estimation, technical complexity, release number, and so to draw.
Use case is important to be followed for every project design.
There are 2 types of use cases :
Informal use case - Consists of a number of paragraphs of the text summarizes the use case.
Fully dressed use case - A formal document based on a detailed template with fields for the various departments, and it is the most common understanding of the meaning of a use case. Fully dressed use cases in detail in the following article on the use case templates.

Some software development processes requires nothing more than a simple use case to define requirements. However, a few other development processes requires detailed use cases to define requirements. The larger and more complex the project, the more likely it will be necessary to implement use cases to be used.

The level of detail in use case is likely to differ according to the progress of the project. The initial use cases may be short, but if the development expands the use cases may have more details. This reflects the different requirements of use case. Initially, they just need to be short, which is used to position the business requirement of the user to summarize. But later in the process, developers must be much more specific and detailed guidance.

The Rational Unified Process invite developers a brief description of the use case diagram use case writing, with an informal description of comments and a detailed description of the flow of events in a textual analysis. Anyone who can usually be used to input the appropriate instrument Like UML , SYSML etc...

Use Cases are used to determine the interactions between external actors and the system under consideration a goal. An actor gives a role played by one person or thing as the interaction with the system .The same person using the system can be represented as different actors, because they play different roles .
Different Actors :

Primary Actor - meets the user goals by using the services of the Sud (System under reservation).
Ex: "checkout" process into a sales system.
Secondary Actor - Provides a service to the Sud. Ex: "Automatic payment authorization service.

Outdoor Drama Actor - Have an interest in the behavior of the system, but is not primary or secondary. Ex: a government tax agency.

A business use case is specified in the technology free terminology system treated as a black box and describes the business process through its business actors , used to meet their objectives (eg handling of payments to achieve cost report approval, Corporate Real Estate Management). The company uses a procedure which case value to the business actor describes, and describes what the process is not. Business Process Mapping is another method for this level of business description.

A system use case describes a system that automates a company uses the event or process. It is usually described on the system call level and specify the function or service that the system provides for the actor. The system uses case details that the system will do in response to the actions of an actor. For this reason it is recommended that system use case specification begin with a verb like closing payment, creating vocher etc…

So, Interview questions and answers will let to know for the faq related to the Business Analyst, Analysis etc...