In process models a task is a small, manageable unit of work to be completed. The completion is usually assigned to a role. The intentional output of a task is called a work product (such as test cases, source code, internal documentation). Completing any given task requires resources (e. g. time, people, technology, knowledge, money)

• Write source code for a feature
• Design a feature
• Write documentation
• Install a library
• Test a feature

In software development tasks are almost always interrelated. A task can depend on another task in the sense that the later must be finished before the former can be started, because the output (work product) of the former is the input of the later. This relation gives a structure to any set of tasks. The right order of tasks is mainly specified by this structure. Not taking task dependencies into account can result in serious waste of resources.