Story mapping is a top-down approach of requirement gathering and is represented as a tree. Story mapping starts from an overarching vision. A vision is achieved via goals. Goals are reached by completing activities. And to complete an activity, users needs to perform tasks. And these tasks can be transformed into user stories for software development.
Story Map Structure: Goals > Activities > Tasks > Stories
Lets take an example of an online store application’s one of the goal ‘Find product’ and build a branch of a story map to understand it better,
To achieve goal ‘Find product’ there are multiple ways such as ‘Browse through product category tree’, ‘Free text search’, ‘Promoted products’. Lets take one approach ‘Browse through product category tree’ to build our story map,
now to complete activity of reaching a required product, user needs to do perform certain tasks,
now this tasks can be converted to user stories for software development,
like this continue to deep dive each branch of the story map starting from goals and build the whole story map. In my experience building full story map takes from 3 days to 2 weeks based on project size and complexity.