As civil engineering emerged and large structures were created, the practice of modeling and designing became really important. The same happened with software development. Nowadays, software is everywhere: in your computer, mobile phone, TV, car, and so on. As the uses of software expanded, software development became increasingly complex and expensive, requiring both time and money.

Software modeling and design are important parts of the software development life cycle. If you have an idea and you are planning to start a software project, the first thing you should do is design and model the software, not just jump into writing the code. This will give you a high-level view of the software and the opportunity to architect it in such a way that it will be easy to extend and modify. If you don't carry out modeling beforehand, you might end up in a situation where you have to restructure your software architecture, which could be very expensive.

The topics that we will cover in this chapter are as follows:

• The importance of design diagrams
• Different Unified Modeling Language (UML) diagrams
• Class diagrams
• Use case diagrams
• Sequence diagrams