UX Design Processes - Differences between user stories / task Models / Use Cases etc

Question

I'm getting really confused with the differences between some of these UX design processes. There seems to be so many methods that seem very similar (to me) and descriptions about each process all seem quite vague.

Can someone please help me understand the differences between these different processes:

• User Stories
• Use Cases
• Task Model
• User Flow

Also at what stage roughly should they be completed. I think the confusion has come in play from looking at various UX guides and each one being quite different.

Answer 1

As you already mentioned, even if you might find Wiki entries, the borders of what is included and what not are kind of blurry. I re-ordered the items because of context - this is the consensus that I use for my day-to-day worklife:

• Use Cases: A feature- or part-of-the-site- usage scenario. If you take use cases for a shopping cart, these would be: 1) Save items for later; 2) Create a list of items I want to buy; 3) Items I would like to send to a friend | This helps getting a deeper understanding of what needs to be in the concept. Use cases often are put into context of business value: Is a use case relevant due to investment cost? For me, this is a starter and a prioritization tool
• User Stories: From the perspective of a user, the process is told. This can be used to create scenarios from different angles. Taking the cart example again: "Me as a user, I would like to check out my items and delete them if I do not like them anymore." - another perspective could be the supplier perspective: "Me as a product supplier, I do not want the items in the cart be reserved for certain users, because I can not justify costs in front of my stakeholder then." In 'story mode', this can bring different perspectives to a scenery.
• User Flow: If you know a little about UML - this is it. A user flow is a description of the different states a user can have while within the observed feature. The example again: A user can enter the cart from the catalog, the product detail page and over a newsletter reminder. Within the cart, he can change quantity and color of the products. Exits of the cart are: Main navigation, going to checkout, ... etc. This view brings up different scenarios and helps getting the feature embedded in the live environment. You could discover that the user, coming from the newsletter, does not have all information in the cart to successfully check out, while a product page entry has.
• Task Model: In my work life, this did not happen so much along my way, since imo it is very similar to user flows. It focuses on tasks, thus actions - while the user flow also takes on STATES and page features the user can have and use.

Again, I do not think that this is the scientific definition. "Use Case" and "User Story" anyhow are frequently mis-used by stakeholders that want to express THEIR needs and try to project it on the customer. The same goes for designers that want to justify their design by invoking use cases.