This paper presents an overview of the Rational Unified Process
Ô The Rational Unified Process is a software engineering process, delivered through a web-enabled, searchable knowledge base. The process enhances team productivity and delivers software best practices via guidelines, templates and tool mentors for all critical software lifecycle activities. The knowledge base allows development teams to gain the full benefits of the industry-standard Unified Modeling Language (UML).What is the Rational Unified Process?
The Rational Unified Process is a Software Engineering Process. It provides a disciplined approach to assigning tasks and responsibilities within a development organization. Its goal is to ensure the production
of high-quality software that meets the needs of its end-users, within a predictable schedule and budget.
[11, 13]
The Rational Unified Process is a process product, developed and maintained by Rational® Software. The development team for the Rational Unified Process are working closely with customers, partners, Rational's
product groups as well as Rational's consultant organization, to ensure that the process is continuously updated and improved upon to reflect recent experiences and evolving and proven best practices.
The Rational Unified Process enhances team productivity, by providing every team member with easy access to a knowledge base with guidelines, templates and tool mentors for all critical development
activities. By having all team members accessing the same knowledge base, no matter if you work with requirements, design, test, project management, or configuration management, we ensure that all team members share a common language, process and view of how to develop software.
The Rational Unified Process activities create and maintain models. Rather than focusing on the production of large amount of paper documents, the Unified Process emphasizes the development and maintenance of
modelssemantically rich representations of the software system under development. [3, 7, 8]
The Rational Unified Process is a guide for how to effectively use the Unified Modeling Language (UML). The UML is a industry-standard language that allows us to clearly communicate requirements,
architectures and designs. The UML was originally created by Rational Software, and is now maintained by the standards organization Object Management Group (OMG). [4]
The Rational Unified Process is supported by tools, which automate large parts of the process. They are
used to create and maintain the various artifactsmodels in particularof the software engineering
process: visual modeling, programming, testing, etc. They are invaluable in supporting all the bookkeeping
associated with the change management as well as the configuration management that accompanies each
iteration.
The Rational Unified Process is a configurable process. No single process is suitable for all software development. The Unified Process fits small development teams as well as large development organizations. The Unified Process is founded on a simple and clear process architecture that provides
commonality across a family of processes. Yet, it can be varied to accommodate different situations. It contains a Development Kit, providing support for configuring the process to suit the needs of a given
organization.
The Rational Unified Process captures many of the best practices in modern software development in a form that is suitable for a wide range of projects and organizations. Deploying these best practices using
the Rational Unified Process as your guide offers development teams a number of key advantages. In next section, we describe the six fundamental best practices of the Rational Unified Process.
Effective Deployment of 6 Best Practices
The Rational Unified Process describes how to effectively deploy commercially proven approaches to software development for software development teams. These are called best practices not so much
because you can precisely quantify their value, but rather, because they are observed to be commonly used in industry by successful organizations. The Rational Unified Process provides each team member with the
guidelines, templates and tool mentors necessary for the entire team to take full advantage of among others the following best practices:
1. Develop software iteratively
2. Manage requirements
3. Use component-based architectures
4. Visually model software
5. Verify software quality
6. Control changes to software
Develop Software Iteratively: Given todays sophisticated software systems, it is not possible to sequentially first define the entire problem, design the entire solution, build the software and then test the product at the end. An iterative approach is required that allows an increasing understanding of the problem through successive refinements, and to incrementally grow an effective solution over multiple iterations.
The Rational Unified Process supports an iterative approach to development that addresses the highest risk items at every stage in the lifecycle, significantly reducing a projects risk profile. This iterative approach
helps you attack risk through demonstrable progress¾frequent, executable releases that enable continuous end user involvement and feedback. Because each iteration ends with an executable release, the development team stays focused on producing results, and frequent status checks help ensure that the
project stays on schedule. An iterative approach also makes it easier to accommodate tactical changes in requirements, features or schedule.
Manage Requirements: The Rational Unified Process describes how to elicit, organize, and document required functionality and constraints; track and document tradeoffs and decisions; and easily capture and
communicate business requirements. The notions of use case and scenarios proscribed in the process has proven to be an excellent way to capture functional requirements and to ensure that these drive the design,
implementation and testing of software, making it more likely that the final system fulfills the end user needs. They provide coherent and traceable threads through both the development and the delivered system.
Use Component-based Architectures The process focuses on early development and baselining of a robust executable architecture, prior to committing resources for full-scale development. It describes how
to design a resilient architecture that is flexible, accommodates change, is intuitively understandable, and promotes more effective software reuse. The Rational Unified Process supports component-based software
development. Components are non-trivial modules, subsystems that fulfill a clear function. The Rational Unified Process provides a systematic approach to defining an architecture using new and existing components. These are assembled in a well-defined architecture, either ad hoc, or in a component
infrastructure such as the Internet, CORBA, and COM, for which an industry of reusable components is emerging.
Visually Model Software The process shows you how to visually model software to capture the structure and behavior of architectures and components. This allows you to hide the details and write code
using graphical building blocks. Visual abstractions help you communicate different aspects of your software; see how the elements of the system fit together; make sure that the building blocks are consistent with your code; maintain consistency between a design and its implementation; and promote unambiguous communication. The industry-standard Unified Modeling Language (UML), created by Rational Software, is the foundation for successful visual modeling.
Verify Software Quality Poor application performance and poor reliability are common factors which dramatically inhibit the acceptability of todays software applications. Hence, quality should be reviewed
with respect to the requirements based on reliability, functionality, application performance and system performance. The Rational Unified Process assists you in the planning, design, implementation, execution, and evaluation of these test types. Quality assessment is built into the process, in all activities, involving all participants, using objective measurements and criteria, and not treated as an afterthought or a separate activity performed by a separate group.
Control Changes to Software The ability to manage change¾making certain that each change is acceptable, and being able to track changes¾is essential in an environment in which change is inevitable.
The process describes how to control, track and monitor changes to enable successful iterative development. It also guides you in how to establish secure workspaces for each developer by providing isolation from changes made in other workspaces and by controlling changes of all software artifacts (e.g., models, code, documents, etc.). And it brings a team together to work as a single unit by describing how to automate integration and build management.
Two Dimensions
The process can be described in two dimensions, or along two axis:
· the horizontal axis represents time and shows the dynamic aspect of the process as it is enacted, and it is expressed in terms of cycles, phases, iterations, and milestones.
· the vertical axis represents the static aspect of the process: how it is described in terms of activities, artifacts, workers and workflows.
Phases and Iterations - The Time Dimension
This is the dynamic organization of the process along time.
The software lifecycle is broken into cycles, each cycle working on a new generation of the product. The Rational Unified Process divides one development cycle in four consecutive phases
Inception phase
Elaboration phase
Construction phase
Transition phase
Each phase is concluded with a well-defined milestonea point in time at which certain critical decisions must be made, and therefore key goals must have been achieved.
Inception Phase
During the inception phase, you establish the business case for the system and delimit the project scope. To accomplish this you must identify all external entities with which the system will interact (actors) and
define the nature of this interaction at a high-level. This involves identifying all use cases and describing a few significant ones. The business case includes success criteria, risk assessment, and estimate of the
resources needed, and a phase plan showing dates of major milestones. The outcome of the inception phase is:
A vision document: a general vision of the core projects requirements, key features, and main constraints.
An initial use-case model (10%-20% complete).
An initial project glossary (may optionally be partially expressed as a domain model).
An initial business case, which includes business context, success criteria (revenue projection, market recognition, and so on), and financial forecast.
An initial risk assessment.
A project plan, showing phases and iterations.
A business model, if necessary.
One or several prototypes.
At the end of the inception phase is the first major project milestone: the Lifecycle Objectives Milestone.
The evaluation criteria for the inception phase are:
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.
· Actual expenditures versus planned expenditures.
The project may be cancelled or considerably re-thought if it fails to pass this milestone.
Construction Transition
The purpose of the elaboration phase is to analyze the problem domain, establish a sound architectural foundation, develop the project plan, and eliminate the highest risk elements of the project. To accomplish
these objectives, you must have the mile wide and inch deep view of the system. Architectural decisions have to be made with an understanding of the whole system: its scope, major functionality and nonfunctional requirements such as performance requirements.
It is easy to argue that the elaboration phase is the most critical of the four phases. At the end of this phase, the hard engineering is considered complete and the project undergoes its most important day of
reckoning: the decision on whether or not to commit to the construction and transition phases. For most projects, this also corresponds to the transition from a mobile, light and nimble, low-risk operation to a
high-cost, high-risk operation with substantial inertia. While the process must always accommodate changes, the elaboration phase activities ensure that the architecture, requirements and plans are stable enough, and the risks are sufficiently mitigated, so you can predictably determine the cost and schedule for the completion of the development. Conceptually, this level of fidelity would correspond to the level necessary for an organization to commit to a fixed-price construction phase.
In the elaboration phase, an executable architecture prototype is built in one or more iterations, depending on the scope, size, risk, and novelty of the project. This effort should at least address the critical use cases
identified in the inception phase, which typically expose the major technical risks of the project. While an evolutionary prototype of a production-quality component is always the goal, this does not exclude the
development of one or more exploratory, throw-away prototypes to mitigate specific risks such as design/requirements trade-offs, component feasibility study, or demonstrations to investors, customers, and end-users.
The outcome of the elaboration phase is:
A use-case model (at least 80% complete) all use cases and actors have been identified, and most use-case descriptions have been developed.
Supplementary requirements capturing the non functional requirements and any requirements that are not associated with a specific use case.
A Software Architecture Description.
An executable architectural prototype.
A revised risk list and a revised business case.
A development plan for the overall project, including the coarse-grained project plan, showing iterations and evaluation criteria for each iteration.
An updated development case specifying the process to be used.
A preliminary user manual (optional).
The main evaluation criteria for the elaboration phase involves the answers to these questions:
Is the vision of the product stable?
Is the architecture stable?
Does the executable demonstration show that the major risk elements have been addressed and credibly resolved?
Is the plan for the construction phase sufficiently detailed and accurate? Is it backed up with a credible basis of estimates?
Do all stakeholders agree that the current vision can be achieved if the current plan is executed to develop the complete system, in the context of the current architecture?
· Is the actual resource expenditure versus planned expenditure acceptable?
The project may be aborted or considerably re-thought if it fails to pass this milestone.
Construction Phase
During the construction phase, all remaining components and application features are developed and integrated into the product, and all features are thoroughly tested. The construction phase is, in one sense, a manufacturing process where emphasis is placed on managing resources and controlling operations to optimize costs, schedules, and quality. In this sense, the management mindset undergoes a transition from the development of intellectual property during inception and elaboration, to the development of
deployable products during construction and transition.
Many projects are large enough that parallel construction increments can be spawned. These parallel activities can significantly accelerate the availability of deployable releases; they can also increase the complexity of resource management and workflow synchronization. A robust architecture and an
understandable plan are highly correlated. In other words, one of the critical qualities of the architecture is its ease of construction. This is one reason why the balanced development of the architecture and the plan is stressed during the elaboration phase.
The outcome of the construction phase is a product ready to put in hands of its end-users. At minimum, it consists of:
The software product integrated on the adequate platforms.
The user manuals.
A description of the current release.
At the end of the construction phase is the third major project milestone (Initial Operational Capability Milestone). At this point, you decide if the software, the sites, and the users are ready to go operational,
without exposing the project to high risks. This release is often called a beta release.
The evaluation criteria for the construction phase involve answering these questions:
Is this product release stable and mature enough to be deployed in the user community?
Are all stakeholders ready for the transition into the user community?
· Are the actual resource expenditures versus planned expenditures still acceptable?
Transition may have to be postponed by one release if the project fails to reach this milestone.
Transition
The purpose of the transition phase is to transition the software product to the user community. Once the product has been given to the end user, issues usually arise that require you to develop new releases, correct
some problems, or finish the features that were postponed.
The transition phase is entered when a baseline is mature enough to be deployed in the end-user domain.
This typically requires that some usable subset of the system has been completed to an acceptable level of quality and that user documentation is available so that the transition to the user will provide positive
results for all parties. This includes:
beta testing to validate the new system against user expectations
parallel operation with a legacy system that it is replacing
conversion of operational databases
training of users and maintainers
roll-out the product to the marketing, distribution, and sales teams
The transition phase focuses on the activities required to place the software into the hands of the users.
Typically, this phase includes several iterations, including beta releases, general availability releases, as well as bug-fix and enhancement releases. Considerable effort is expended in developing user-oriented
documentation, training users, supporting users in their initial product use, and reacting to user feedback.
At this point in the lifecycle, however, user feedback should be confined primarily to product tuning, configuring, installation, and usability issues.
The primary objectives of the transition phase include:
Achieving user self-supportability
Achieving stakeholder concurrence that deployment baselines are complete and consistent with the evaluation criteria of the vision
Iterations
Each phase in the Rational Unified Process can be further broken down into iterations. An iteration is a complete development loop resulting in a release (internal or external) of an executable product, a subset of the final product under development, which grows incrementally from iteration to iteration to become the final system.
Benefits of an iterative approach
Compared to the traditional waterfall process, the iterative process has the following advantages:
· Risks are mitigated earlier
· Change is more manageable
· Higher level of reuse
· The project team can learn along the way
· Better overall quality
