To understand UP, we must first go through some basic concepts that are the foundations of UP. UP defines 4 basic semantics in its lifecycle.

1.    Roles: This describes a role played by an individual or a team within a project. Each role can include many individuals and multiple teams. Examples of roles are QA officer, developer, project manager, tester, etc.

2.    Activities: This describes the tasks that are performed by the different roles in the life cycle.

3.    Artifacts: This describes the things that act as input to the project or as an output from it. This includes source code, executables, different forms of documentation, coding standards, company forms and so on.

4.    Workflows: These are sequences of related activities performed by specific roles. These are sometimes referred to as disciplines. This is the corner stone concept behind UP. We will discuss the workflows present in UP in later sections.

In addition to the above semantics, UP is characterized by being:

1.    Requirements - Centric: UP thoroughly focuses on the user requirements collected at the beginning of the project and refined throughout the life cycle. We will discuss in brief this topic later in the article and in more detail in a later article.

2.    Architecture driven: At the core of the UP is developing robust system architecture of the software we are building.

3.    Iterative and incremental: This means that the UP breaks the project into small sub projects (iterations) and delivers the software in parts (the increments).  This is where the UP varies from the old waterfall model of software development. We will indulge in this concept in more detail in the next section.