Ideally, the interaction design process begins when the requirements process begins. This is because:

• Collecting and understanding user requirements is a critical component of successful software ( Good example of why interaction design is important )

• Producing a readable, understandable and complete requirements document is necessary for a successful project.
• A properly created use case document is easily read by stakeholders and clients, yet is detailed enough to provide full guidance to management, software engineers and interaction designers.

Requirements Phase

• Task analysis collects feedback from real users; extracting important requirements that fall outside of business needs yet are necessary for successful software.
• The output of user task analysis is combined with business requirements and system constraints to create a complete use case document .
• Use cases combined with system requirements forms a complete requirements document.

Design Phase

Once the requirements phase is complete, interaction design plays a vital role in the design phase of a software project.

• Software prototypes are created using mockup tools giving a full understanding of what the final interface will look and feel like.
• Prototypes are an excellent way to get full client buy-in. As well, they serve as detailed input for software engineers and as the perfect input to usability testing.

Testing

Usability testing is the ultimate test of the efficiency and ease-of-use of a software interface. Generally, usability testing is completed at three points in the software engineering process:

• Once a user interface prototype has been created
• When the full software implementation is near completion
• Once a piece of software is in real world use

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