Rational Unified Process (RUP) is an iterative software development process framework created by the Rational Software Corporation. Combining the experience base of companies led to the articulation of six best practices for modern software engineering:
1. Develop iteratively
2. Manage requirements
3. Employ a component-based architecture
4. Model software visually
5. Continuously verify quality
6. Control changes
These best practices were used by Rational's team to help customers improve the quality and predictability of their software development efforts. The resulting "Rational Unified Process" (RUP) completed a strategic tripod for Rational:
- a tailorable process that guided development
- tools that automated the application of that process
- services that accelerated adoption of both the process and the tools.
RUP building blocks
RUP is based on a set of building blocks and content elements, describing what is to be produced, the necessary skills required and the step-by-step explanation describing how specific development goals are to be achieved. The main building blocks, or content elements, are the following:
- Roles (who) – A role defines a set of related skills, competencies and responsibilities.
- Work products (what) – A work product represents something resulting from a task, including all the documents and models produced while working through the process.
- Tasks (how) – A task describes a unit of work assigned to a Role that provides a meaningful result. Within each iteration, the tasks are categorized into nine disciplines:
Six "engineering disciplines"
- Business modelling
- Requirements
- Analysis and design
- Implementation
- Test
- Deployment
Three "supporting disciplines"
- Configuration and change management
- Project management
- Environment
Four project life-cycle phases
The RUP has determined a project life-cycle consisting of four phases. These phases allow the process to be presented at a high level in a similar way to how a 'waterfall'-styled project might be presented, although in essence the key to the process lies in the iterations of development that lie within all of the phases. Also, each phase has one key objective and milestone at the end that denotes the objective being accomplished. The visualization of RUP phases and disciplines over time is referred to as the RUP hump chart.
RUP phases and disciplines.
Inception phase
The primary objective is to scope the system adequately as a basis for validating initial costing and budgets. In this phase the business case which includes business context, success factors (expected revenue, market recognition, etc.), and financial forecast is established. To complement the business case, a basic use case model, project plan, initial risk assessment and project description (the core project requirements, constraints and key features) are generated. After these are completed, the project is checked against the following criteria:
• Stakeholder concurrence on scope definition and cost/schedule estimates.
• Requirements understanding as evidenced by the fidelity of the primary use cases.
• Credibility of the cost/schedule estimates, priorities, risks, and development process.
• Depth and breadth of any architectural prototype that was developed.
• Establishing a baseline by which to compare actual expenditures versus planned expenditures.
If the project does not pass this milestone, called the lifecycle objective milestone, it either can be cancelled or repeated after being redesigned to better meet the criteria
Elaboration phase
The primary objective is to mitigate the key risk items identified by analysis up to the end of this phase. The elaboration phase is where the project starts to take shape. In this phase the problem domain analysis is made and the architecture of the project gets its basic form.
The outcome of the elaboration phase is:
• A use-case model in which the use-cases and the actors have been identified and most of the use-case descriptions are developed. The use-case model should be 80% complete.
• A description of the software architecture in a software system development process.
• An executable architecture that realizes architecturally significant use cases.
• Business case and risk list which are revised.
• A development plan for the overall project.
• Prototypes that demonstrably mitigate each identified technical risk.
• A preliminary user manual (optional)
This phase must pass the lifecycle architecture milestone criteria answering the following questions:
• Is the vision of the product stable?
• Is the architecture stable?
• Does the executable demonstration indicate that major risk elements are addressed and resolved?
• Is the construction phase plan sufficiently detailed and accurate?
• Do all stakeholders agree that the current vision can be achieved using current plan in the context of the current architecture?
• Is the actual vs. planned resource expenditure acceptable?
If the project cannot pass this milestone, there is still time for it to be cancelled or redesigned. However, after leaving this phase, the project transitions into a high-risk operation where changes are much more difficult and detrimental when made.
The key domain analysis for the elaboration is the system architecture
Construction phase
The primary objective is to build the software system. In this phase, the main focus is on the development of components and other features of the system. This is the phase when the bulk of the coding takes place. In larger projects, several construction iterations may be developed in an effort to divide the use cases into manageable segments that produce demonstrable prototypes.
This phase produces the first external release of the software. Its conclusion is marked by the initial operational capability milestone.
Transition phase
The primary objective is to 'transit' the system from development into production, making it available to and understood by the end user. The activities of this phase include training the end users and maintainers and beta testing the system to validate it against the end users' expectations. The product is also checked against the quality level set in the Inception phase.
If all objectives are met, the product release milestone is reached and the development cycle is finished
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The four roles in the RUP Test discipline
Profile of the iterative (modern) approach compared with the waterfall approach
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