Rational Unified Process

The Rational Unified Process (RUP) is a popular iterative software development process created by the Rational Software Corporation, now a division of IBM. The RUP is an extensive refinement of the (generic) Unified Process.

The RUP is not a single concrete prescriptive process, but rather an adaptable process framework. It is intended to be tailored, in the sense that development organizations and software project teams will select the elements of the process that are appropriate for their needs.

The Rational Unified Process (RUP) is also a software process product, originally developed by Rational Software, and now available from IBM. The product includes a hyperlinked knowledge base with sample artifacts and detailed descriptions for many different types of activities. RUP is included in the IBM Rational Method Composer (RMC) product which allows customization of the process.

Background

History

The roots of the Rational Process go back to the original spiral model of Barry Boehm. Ken Hartman, one of the key RUP contributors, collaborated with Boehm on research and writing. The Rational Approach was developed at Rational Software in the 1980s and 1990s.

In 1995 Rational Software acquired the Swedish Company Objectory AB. The Rational Unified Process was the result of the merger of the Rational Approach and the Objectory process developed by Objectory founder Ivar Jacobson. The first results of that merger was the Rational Objectory Process, designed to an Objectory-like process, but suitable to wean Objectory users to the Rational Rose tool. When that goal was accomplished, the name was changed. The first version of the Rational Unified Process, version 5.0, was released in 1998. The chief architect was Philippe Kruchten.

Design Objectives

The creators and developers of the process focused on diagnosing the characteristics of different failed software projects; by doing so they tried to recognize the root causes of these failures. They also looked at the existing software engineering processes and their solutions for these symptoms.

A representative list of failure causes includes the following:

* Ad hoc requirements management
* Ambiguous and imprecise communication
* Brittle architecture (architecture that does not work properly under stress)
* Overwhelming complexity
* Undetected inconsistencies in requirements, designs, and implementations
* Insufficient testing
* Subjective assessment of project status
* Failure to attack risks
* Uncontrolled change propagation
* Insufficient automation

Project failure is caused by a combination of several symptoms, though each project fails in a unique way. The outcome of their study was a system of software best practices they named the Rational Unified Process.

The Process was designed with the same techniques the team used to design software; it has an underlying object-oriented model, using Unified Modeling Language (UML).

Principles and Best Practices

RUP is based on a set of software development principles and best practices, for instance:

1. Develop software iteratively
2. Manage requirements
3. Use component based architecture
4. Visually model software
5. Verify software quality
6. Control changes to software


Develop software iteratively

Given the time it takes to develop large sophisticated software systems it is not possible to define the problem and build the solution in a single step. Requirements will often change throughout a project's development, due to architectural constraints, customer's needs or a greater understanding of the original problem. Iteration allows the project to be successively refined and addresses a project's highest risk items as the highest priority task. Ideally each iteration ends up with an executable release – this helps reduce a project's risk profile, allows greater customer feedback and helps developers stay focused.

The RUP uses iterative and incremental development for the following reasons:

* Integration is done step by step during the development process, limiting it to fewer elements.
* Integration is less complex, making it more cost effective.
* Parts are separately designed and/or implemented and can be easily identified for later reuse.
* Requirement changes are noted and can be accommodated.
* Risks are attacked early in development since each iteration gives the opportunity for more risks to be identified.
* Software architecture is improved by repeated scrutiny.

Using iterations, a project will have one overall phase plan, but multiple iteration plans. Involvement from stakeholders is often encouraged at each milestone. In this manner, milestones serve as a means to obtain stakeholder buy in while providing a constant measure against requirements and organizational readiness for the pending launch.

Manage requirements

Requirements Management in RUP is concerned with meeting the needs of end users by identifying and specifying what they need and identifying when those needs change. Its benefits include the following:

* The correct requirements generate the correct product; the customer's needs are met.
* Necessary features will be included, reducing post-development cost.

RUP suggests that the management of requirements has the following activities:

Analyze the problem is about agreeing on the problem and creating the measures that will prove its value to the organization.

Understand stakeholder needs is about sharing the problem and value with key stakeholders and finding out what their needs are surrounding the solution idea.

Define the system is about creating features from needs and outlining use cases, activities which show nicely the high-level requirements and the overall usage model of the system.

Manage the scope of the system is about modifying the scope of what you will deliver based on results so far and selecting the order in which to attack the use-case flows.

Refine the system definition is about detailing use-case flows with the stakeholders in order to create a detailed Software Requirements Specification (SRS) that can serve as the contract between your team and your client and that can drive design and test activities.

Manage changing requirements is about how to handle incoming requirement changes once the project has begun.

Use component-based architecture

Component-based architecture creates a system that is easily extensible, intuitively understandable and promotes software reuse. A component often relates to a set of objects in object-oriented programming.

Software architecture is increasing in importance as systems are becoming larger and more complex. RUP focuses on producing the basic architecture in early iterations. This architecture then becomes a prototype in the initial development cycle. The architecture evolves with each iteration to become the final system architecture. RUP also asserts design rules and constraints to capture architectural rules. By developing iteratively it is possible to gradually identify components which can then be developed, bought or reused. These components are often assembled within existing infrastructures such as CORBA and COM, or Java EE.

Visually model software

Abstracting your programming from its code and representing it using graphical building blocks is an effective way to get an overall picture of a solution. Using this representation, technical resources can determine how best to implement a given set of inter-related logics. It also builds an intermediary between the business process and actual code through information technology. A model in this context is a visualization and at the same time a simplification of a complex design. RUP specifies which models are necessary and why.

The Unified Modeling Language (UML) can be used for modeling Use-Cases, Class diagrams and other objects. RUP also discusses other ways to build models.
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Verify software quality

Quality assessment is the most common failing point of all software projects, since it is often an afterthought and sometimes even handled by a different team. RUP assists in planning quality control and assessment by building it into the entire process and involving all members of a team. No worker is specifically assigned to quality; RUP assumed that each member of the team is responsible for quality during the entire process. The process focuses on meeting the expected level of quality and provides test workflows to measure this level.

Control changes to software

In all software projects, change is inevitable. RUP defines methods to control, track and monitor changes. RUP also defines secure workspaces, guaranteeing a software engineer's system will not be affected by changes in another system. This concept ties in heavily with component based architectures.
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Project Lifecycle
A typical project profile showing the relative sizes of the four phases
A typical project profile showing the relative sizes of the four phases

The Rational Unified Process divides a project into four phases.

* Inception Phase
* Elaboration Phase
* Construction Phase
* Transition Phase



The Inception Phase

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.
* Actual expenditures versus planned expenditures.

If the project does not pass this milestone, called the Lifecycle Objective Milestone, it can either be cancelled or it can repeat this phase after being redesigned to better meet the criteria.

The Elaboration 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.

This phase must pass the Lifecycle Architecture Milestone by meeting the following criteria:

* 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.

If the project cannot pass this milestone, there is still time for it to be cancelled or redesigned. After leaving this phase, the project transitions into a high-risk operations where changes are much more difficult and detrimental when made.
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The Construction Phase

In this phase the main focus goes to the development of components and other features of the system being designed. 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.

The Transition Phase

In the transition phase, the product has moved from the development organization to the end user. The activities of this phase include training of the end users and maintainers and beta testing of 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 it does not meet this level, or the standards of the end users, the entire cycle in this phase begins again.

If all objectives are met, the Product Release Milestone is reached and the development cycle ends.

Disciplines and Workflows
The Rational Unified Process
The Rational Unified Process

RUP is based on a set of building blocks, or content elements, describing what is to be produced, the necessary skills required and the step-by-step explanation describing how specific development goals are 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.

The RUP lifecycle has been created by assembling the content elements described above into semi-ordered sequences. Consequently the RUP lifecycle is available as a work breakdown structure, which could be customized to address the specific needs of a project. The RUP lifecycle organizes the tasks into phases and iterations. Within each iteration, the tasks are categorized into nine Disciplines:

Engineering Disciplines:

* Business modeling discipline
* Requirements discipline
* Analysis and design discipline
* Implementation discipline
* Test discipline
* Deployment discipline

Supporting Disciplines:

* Configuration and change management discipline
* Project management discipline
* Environment discipline


Business Modeling Discipline

Organizations are becoming more dependent on IT systems, making it imperative that information system engineers know how the applications they are developing fit into the organization. Businesses invest in IT when they understand the competitive advantage and value added by the technology.

The aim of business modeling is to first establish a better understanding and communication channel between business engineering and software engineering. Understanding the business means that software engineers must understand the structure and the dynamics of the target organization (the client), the current problems in the organization and possible improvements. They must also ensure a common understanding of the target organization between customers, end users and developers.

Business modeling explains how to describe a vision of the organization in which the system will be deployed and how to then use this vision as a basis to outline the process, roles and responsibilities.

Requirements Discipline

The goal of the Requirements is to describe what the system should do and allows the developers and the customer to agree on that description. To achieve this, analysts elicit, organize, and document required functionality and constraints; track and document tradeoffs and decisions. A Vision document is created, and stakeholder needs are elicited. Actors are identified, representing the users, and any other system that may interact with the system being developed. Use cases are identified, representing the behavior of the system. Because use cases are developed according to the actor's needs, the system is more likely to be relevant to the users.

Analysis and Design Discipline

The goal of Analysis and Design is to show how the system will be realized in the implementation phase. You want to build a system that:

* Performs—in a specific implementation environment—the tasks and functions specified in the use-case descriptions.
* Fulfills all its requirements.
* Easy to change if and when its functional requirements change .

Analysis and Design results in a design model and optionally an analysis model. The design model serves as an abstraction of the source code; that is, the design model acts as a 'blueprint' of how the source code is structured and written.The design model consists of design classes structured into design packages and design subsystems with well-defined interfaces, representing what will become components in the implementation. It also contains descriptions of how objects of these design classes collaborate to perform use cases.

Implementation Discipline

The purposes of implementation are:

* To define the organization of the code, in terms of implementation subsystems organized in layers.
* To implement classes and objects in terms of components (source files, binaries, executables, and others).
* To test the developed components as units.
* To integrate the results produced by individual implementers (or teams), into an executable system.

The system is realized through implementation of components. The Rational Unified Process describes how you reuse existing components, or implement new components with well defined responsibility, making the system easier to maintain, and increasing the possibilities to reuse
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Test Discipline

The purposes of the Test discipline are:

* To verify the interaction between objects.
* To verify the proper integration of all components of the software.
* To verify that all requirements have been correctly implemented.
* To identify and ensure defects are addressed prior to the deployment of the software

The Rational Unified Process proposes an iterative approach, which means that you test throughout the project. This allows you to find defects as early as possible, which radically reduces the cost of fixing the defect. Test are carried out along three quality dimensions reliability, functionality, application performance and system performance. For each of these quality dimensions, the process describes how you go through the test lifecycle of planning, design, implementation, execution and evaluation.
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Deployment Discipline

The purpose of deployment is to successfully produce product releases, and deliver the software to its end users. It covers a wide range of activities including:

* Producing external releases of the software
* Packaging the software
* Distributing the software
* Installing the software
* Providing help and assistance to users

Although deployment activities are mostly centered around the transition phase, many of the activities need to be included in earlier phases to prepare for deployment at the end of the construction phase.The Deployment and Environment workflows of the Rational Unified Process contain less detail than other workflows.

Configuration and Change Management Discipline

The Change Management discipline in RUP deals with three specific areas:

* Configuration management
* Change request management
* Status and measurement management


Configuration management

Configuration management is responsible for the systematic structuring of the products. Artifacts such as documents and models need to be placed under version control and these changes must be visible. It also keeps track of dependencies between artifacts so all related articles are updated when changes are made.

Change request management

During the system development process many artifacts with several versions exist. CRM keeps track of the proposals for change.

Status and measurement management

Change requests have states such as new, logged, approved, assigned and complete. A change request also has attributes such as root cause, or nature (like defect and enhancement), priority etc. These states and attributes are stored in database so useful reports about the progress of the project can be produced. Rational also has a product to maintain change requests called ClearQuest.
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The IBM Rational Method Composer product

The RUP process framework within IBM Rational Method Composer includes:

* A process content library based on the best practices adopted in thousands of projects worldwide.
* Out-of-the-box delivery processes to provide the project manager with a quick starting point for planning and initiating a project. A delivery process will provide an initial project template, identify what milestones to have in the project, what work products to delivered by each milestone, and what resources are needed for each phase.
* Capability patterns that allow project managers to rapidly add or remove reusable chunks of processes addressing common problems. Since no two projects are alike, project managers need to rapidly modify the process to address the specific project needs.

The IBM Rational Method Composer (RMC) is a commercial product (built on top of Eclipse) for authoring, configuring, viewing, and publishing processes.

RMC has two main purposes:

* RMC is a content management system that provides a common management structure and look and feel for all process content. All content managed in RMC can be published to html and deployed to Web servers for distributed usage.
* RMC provides process engineers and project managers with the capability of selecting, tailoring, and rapidly assembling processes for their concrete development projects. RMC provides catalogs of pre-defined processes (like RUP) for typical project situations that can be adapted to individual needs. It also provides process building blocks called capability patterns that represent best development practices for specific disciplines, technologies, or development styles. These building blocks form a toolkit for quickly assembling processes based on project specific needs. Finally, the documented processes created with RMC can be published and deployed as Web sites. They can also be deployed as project plan templates for IBM Rational Portfolio Manager.

In additional to full RUP, RMC provides RUP plug-ins (extensions to the RUP content that can only be installed on top of RUP) for important areas such as service-oriented architectures (RUP for SOA), systems engineering (RUP for systems engineering), packaged application development (RUP for COTS), program and portfolio management, etc. New delivery processes are added frequently and are made available via the IBM developerWorks Website.

There is an open source version of IBM RMC created as part of the Eclipse Process Framework (EPF) project. The EPF tool contains full process authoring and publishing capabilities. The main difference between EPF and the Rational Method Composer tool is the lack of integrations with other IBM Rational tools such as Rational Portfolio Manager and Rational Software Architect as well as lack of a migration capability from Rational Process Workbench. EPF comes with OpenUP/Basic, a new agile process for small teams applying RUP principles and practices.

Limitations

If the users of RUP do not understand that RUP is a process framework, they may perceive it as a weighty and expensive process. RUP was not intended, not envisioned and not promoted to be used straight "out of the box". The IBM Rational Method Composer product has been created to address this limitation and help process engineers and project managers customize the RUP for their project needs. OpenUP/Basic, the lightweight and open source version of RUP, is another attempt to address this limitation.