According to the BABOK® v3 guide, the purpose of defining the design options is as follows:

In a practical way, you can look at this task as the activities you will perform when you are working out which way to go in terms of implementing the requirements you have prepared in order to achieve the business value. This is referred to as identifying the design options.

Design options generally refer to the steps that will be taken to ensure the solution is delivered.

Design options are not the specific solution functionality but rather the approach that will be taken to deliver the solution.

Let's look at this real-world example.

In this example, there are two design options identified for a small project.

The first design option describes the approach for implementing software changes to an existing system. A micro-phased approach follows, where only three software changes are implemented during every release cycle. 

The second design option describes the decision for implementing a new vendor software component as part of the overall solution. With this design option, it was decided to purchase this vendor software component instead of developing it in-house. The business analyst should consider whether this design option will meet all the requirements for the business stakeholders and whether any trade-offs would need to be identified and managed accordingly.

If any of these tactical design options require any type of trade-offs to be made in order to successfully deliver the solution, the business analyst must aim to ensure that these trade-offs don't impact the requirements in an adverse way.

In the next section, we will discuss the specific elements that the business analyst must include when performing the task of defining the design options.