Dynamic Systems Development Method
Dynamic Systems Development Method (DSDM) is a software development approach originally based upon the Rapid Application Development (RAD) methodology. DSDM is an iterative and incremental approach that emphasizes continuous user involvement. Its goal is to deliver
software systems on time and on budget while adjusting for changing requirements along the development process. DSDM is one of a number of Agile methods for developing software, and it forms a part of the Agile Alliance.
DSDM was developed in the United Kingdom in the 1990s by the DSDM Consortium, an association of vendors and experts in the field of Information System (IS) development created with the objective of "jointly developing and promoting an independent RAD framework" by combining their best-practice experiences. The DSDM Consortium is a not-for-profit, vendor-independent organisation which owns and administers the DSDM framework. The first version was completed in January 1995 and was published in February 1995. The current version in use (as of April 2006) is "Version 4.2: Framework for Business Centered Development", and was released in May 2003. In July 2006, DSDM Public Version 4.2 ( [http://www.dsdm.org www.dsdm.org] ) was made available for individuals to view and use; however, anyone reselling DSDM must still be a member of the not-for-profit consortium.
As an extension of
rapid application development, DSDM focuses on Information Systemsprojects that are characterized by tight schedules and budgets. DSDM addresses the most common failures of information systems projects, including exceeding budgets, missing deadlines, and lack of user involvement and top-management commitment. By encouraging the use of RAD, however, careless adoption of DSDM may increase the risk of cutting too many corners.
DSDM consists of 3 phases: pre-project phase, project life-cycle phase, and post-project phase. The project life-cycle phase is subdivided into 5 stages: feasibility study, business study,
functional modeliteration, design and build iteration, and implementation.
In some circumstances, there are possibilities to integrate practices from other methodologies, such as Rational Unified Process (RUP), Extreme Programming (XP), and
PRINCE2, as complements to DSDM. Another agile method that has some similarity in process and concept to DSDM is Scrum.
There are 9 underlying principles consisting of four foundations and five starting-points.
* User involvement is the main key in running an efficient and effective project, where both users and developers share a workplace, so that the decisions can be made accurately.
* The project team must be empowered to make decisions that are important to the progress of the project without waiting for higher-level approval.
* A focus on frequent delivery of products, with assumption that to deliver something "good enough" earlier is always better than to deliver everything "perfectly" in the end. By delivering product frequently from an early stage of the project, the product can be tested and reviewed where the test record and review document can be taken into account at the next iteration or phase.
* The main criteria for acceptance of a "deliverable" is delivering a system that addresses the current business needs. Delivering a perfect system which addresses all possible business needs is less important that focusing on critical functionalities.
* Development is iterative and incremental and driven by users’ feedback to converge on an effective business solution.
* All changes during the development are reversible.
* The high level scope and requirements should be base-lined before the project starts.
* Testing is carried out throughout the project life-cycle. (See
Test-driven developmentfor comparison).
* Communication and cooperation among all project stakeholders is required to be efficient and effective.
* No system is built perfectly in the first try (see the pareto principle or 80/20 rule). In short, 80% of the business benefit comes from 20% of the design requirements, therefore DSDM starts by implementing this critical 20% first; this may produce a system that provides enough functionality to satisfy the end-users and the remaining 80% can be added in later iterations. This mitigates risk of the project going over deadline and over budget.
* Project delivery should be on time, on budget and with good quality.
* Each step of the development only need be completed far enough for the next step to begin. This allows a new iteration of the project to commence without unnecessary delay. Changes in design can coincide with the changes in demand from the end-users since every iteration of the system is improved incrementally.
Project Managementand Development techniques are incorporated.
* DSDM can be applied in new projects and for expanding current systems.
* Risk assessment should focus on the business functionality being delivered, not on the development process nor its artifacts (such as requirements and design documents).
* Management rewards product delivery rather than task completion.
* Estimation should be based on business functionality instead of lines of code.
=Prerequisitesfor using DSDM=
In order for DSDM to be a success, a number of prerequisites need to be realized. First, there needs to be interactivity between the project team, future end users and higher management. This addresses well known failures of IS development projects due to lack of top management motivation and/or user involvement. The second prerequisite for DSDM projects is that the project can be decomposed in to smaller parts enabling the use of an iterative approach.
Two examples of types of projects for which DSDM is not considered well-suited are:
* Safety-critical projects - the extensive testing and validation found in safety-critical projects conflict with DSDM goals of being on time and on budget.
* Projects that aim to produce re-usable components - the demands on perfection are often too high and conflict with the 80%/20% principle described earlier.
Process-Data Diagram of DSDM Project Life-cycle
Below is the process-data diagram of DSDM as a whole with all of its 5 stages. This diagram depicts the DSDM iterative development, started on functional model iteration, design and build iteration, and implementation phase. The description of each stage will be explained later in this entry.
tage 4: Design and Build Iteration
The main focus of this DSDM iteration is to integrate the functional components from the previous phase into one system that satisfies user needs. It also addresses the non-functional requirements that have been set for the IS. Again testing is an important ongoing activity in this stage. The Design and Build Iteration can be subdivided into four sub-stages:
* Identify Design Prototype: Identify functional and non-functional requirements that need to be in the tested system.
* Agree Schedule: Agree on how and when to realize these requirements.
* Create Design Prototype: Create a system that can safely be handed to end-users for daily use. They investigate, refine, and consolidate the prototype of current iteration within prototyping process are also important in this sub-stage.
* Review Design Prototype: Check the correctness of the designed system. Again testing and reviewing are the main techniques used, since the test records and user’s feedbacks are important to generate the user documentation.
The deliverables for this stage are a Design Prototype during the phase that end users get to test and at the end of the Design and Build Iteration the Tested System is handed over to the next phase. In this stage, the system is mainly built where the design and functions are consolidated and integrated in a prototype. Another deliverable for this stage is a User Documentation.
tage 5: Implementation
In the Implementation stage, the tested system including user documentation is delivered to the users and training of future users is realized. The system to be delivered has been reviewed to include the requirements that have been set in the beginning stages of the project. The Implementation stage can be subdivided into four sub-stages:
* User Approval and Guidelines: End users approve the tested system for implementation and guidelines with respect to the implementation and use of the system are created.
* Train Users: Train future end user in the use of the system.
* Implement: Implement the tested system at the location of the end users.
* Review Business: Review the impact of the implemented system on the business, a central issue will be whether the system meets the goals set at the beginning of the project. Depending on this the project goes to the next phase, the post-project or loops back to one of the preceding phases for further development.
The deliverables for this stage are a Delivered System on location, ready for use by the end users, Trained Users and detailed Project Review Document of the system.
The post-project phase ensures the system operating effectively and efficiently. This is realized by maintenance, enhancements and fixes according to DSDM principles. The maintenance can be viewed as continuing development based on the iterative and incremental nature of DSDM. Instead of finishing the project in one cycle usually the project can return to the previous phases or stages so that the previous step and the deliverable products can be refined.
=CoreTechniques of DSDM=
*TimeboxingTimeboxing is one of the project techniques of DSDM. It is used to support the main goals of DSDM to realize the development of an IS on time, within budget and with the desired quality. The main idea behind timeboxing is to split up the project in portions, each with a fixed budget and a delivery date. For each portion a number of requirements are selected that are prioritized according to the MoSCoW principle. Because time and budget are fixed, the only remaining variables are the requirements. So if a project is running out of time or money the requirements with the lowest priority are omitted. This does not mean that an unfinished product is delivered, because of the pareto principle that 80% of the project comes from 20% of the system requirements, so as long as those most important 20% of requirements are implemented into the system, the system therefore meets the business needs and that no system is built perfectly in the first try.
*MoSCoWMoSCoW represents a way of prioritizing items. In the context of DSDM the MoSCoW technique is used to prioritize requirements. It is an acronym that stands for:: MUST have this requirement to meet the business needs.: SHOULD have this requirement if at all possible, but the project success does not rely on this.: COULD have this requirement if it does not affect the fitness of business needs of the project.: WOULD have this requirement at later date if there is some time left (or in the future development of the system).
*PrototypingThis technique refers to the creation of prototypes of the system under development at an early stage of the project. It enables the early discovery of shortcomings in the system and allows future users to ‘test-drive’ the system. This way good user involvement is realized, one of the key success factors of DSDM, or any System Development project for that matter.
*TestingA third important aspect of the goal of DSDM is the creation of an IS with good quality. In order to realize a solution of good quality, DSDM advocates testing throughout each iteration. Since DSDM is a tool and technique independent method, the project team is free to choose its own test management method, for example [http://eng.tmap.net/Home/ TMap] .
*WorkshopOne of DSDM’s project techniques that aims at bringing the different stakeholders of the project together to discuss requirements, functionalities and mutual understanding. In a workshop the stakeholders come together and discuss the project.
*ModelingThis technique is essential and purposely used to visualise the diagrammatic representation of a specific aspect of the system or business area that is being developed. Modelling gives a better understanding for DSDM project team over a business domain.
*Configuration ManagementA good implementation of this
configuration managementtechnique is important for the dynamic nature of DSDM. Since there is more than one thing being handled at once during the development process of the system, and the products are being delivered frequently at a very fast rate, the products therefore need to be controlled strictly as they achieve (partial) completion.
There are some roles introduced within DSDM environment. It is important that the project members need to be appointed to different roles before they start to run the project. Each role has its own responsibility. The roles are:
* Executive Sponsor So called the “Project Champion”. An important role from the user organization who has the ability and responsibility to commit appropriate funds and resources. This role has an ultimate power to make decisions.
* Visionary The one who has the responsibility to initialize the project by ensuring that essential requirements are found early on. Visionary has the most accurate perception of the business objectives of the system and the project. Another task is to supervise and keep the development process in the right track.
* Ambassador User Brings the knowledge of user community into the project, ensures that the developers receive enough amount of user’s feedbacks during the development process.
* Advisor User Can be any user that represents an important viewpoint and brings the daily knowledge of the project.
* Project Manager Can be anyone from user community or IT staff who manages the project in general.
* Technical Co-ordinator Responsible in designing the system architecture and control the technical quality in the project.
* Team Leader Leads his team and ensures that the team works effectively as a whole.
* Developer Interprete the system requirements and model it including developing the deliverablecodes and build the prototypes.
* Tester Checks the correctness in a technical extents by performing some testings. Tester will have to give some comments and documentation.
* Scribe Responsible to gather and record the requirements, agreements, and decisions made in every workshop.
* Facilitator Responsible in managing the workshops progress, acts as a motor for preparation and communication.
* Specialist Roles Business Architect, Quality Manager, System Integrator, etc.
=Iterativeand Incremental Nature=
Next to timeboxing and prioritizing of requirements, the DSDM also provides an iterative and incremental approach to IS development. This can be seen in the figure depicting the Process Overview above.
The Functional Model Iteration, Design & Build Iteration and Implementation stages can go over their sub stages several times before entering the next stage. Each iteration addresses a set of new functionalities, and every iteration builds on a working predecessor. Each iteration can be undone if needed.
The Process Overview figure also shows arrows going back to previous stages. For example, there is an arrow from Implementation to the Business Study. If a big functionality has been discovered during development that couldn’t be implemented, it might be possible to start all over by defining new requirements in a Business Study. Similarly, there is an arrow from Implementation to the Functional Model Iteration. Functionality might be omitted during a previous Functional Model Iteration because of time or budget constraints. The project should proceed into the post-project phase only when it meets all the requirements defined by the project and business goals.
Because of the iterative nature of DSDM, it is essential to maintain good requirements management and
configuration managementthroughout the entire project. This ensures that the project does implement the requirements that were decided in the early phases of the project.
Critical Success Factors of DSDM
Within DSDM a number of factors are identified as being of great importance to ensure successful projects.
* Factor 1: First there is the acceptance of DSDM by senior management and other employees. This ensures that the different actors of the project are motivated from the start and remain involved throughout the project.
* Factor 2: The second factor follows directly from this and that is the commitment of management to ensure end-user involvement. The prototyping approach requires a strong and dedicated involvement by end user to test and judge the functional prototypes.
* Factor 3: Then there is the project team. This team has to be composed of skillful members that form a stable union. An important issue is the empowerment of the project team. This means that the team (or one or more of its members) has to possess the power and possibility to make important decisions regarding the project without having to write formal proposals to higher management, which can be very time-consuming. In order for the project team to be able to run a successful project, they also need the right technology to conduct the project. This means a development environment, project management tools, etc.
* Factor 4: Finally DSDM also states that a supportive relationship between customer and vendor is required. This goes for both projects that are realized internally within companies or by outside contractors. An aid in ensuring a supporting relationship could be
As explained in the Wikipedia item,
Meta-Modelingtakes a higher level look at methods and techniques. In doing so it offers possibilities for comparing similar methods and techniques and engineering new methods from existing ones.
The Meta data model, depicted below, identifies the concepts and associations between these concepts within DSDM. As can be seen from the figure, two main concepts can be identified, namely the "Phase" and the "Flow" concept. Each "Flow" originates from a "Phase" within DSDM. Flows can be divided up in the sub concepts "Data" and "Product". This subdivision is denoted with a "C", which means that the subdivision is disjoint and complete. In other words, a "Flow" is always either a "Data Flow" or a "Product Flow", but never both. In the situation of DSDM a "Data Flow" can be an arc returning to one of the preceding phases. "Product Flows are tangible goods that result from one of the "Phases" and are the input of the next "Phase", for example reports and prototypes.
Then there is the second concept "Phase" that is also be divided two sub concepts with a complete and disjoint ordering. These sub concepts are the "Sequential" and the "Iterative Phases". As was explained in an earlier section, DSDM starts with two sequential phases, The Feasibility and Business Study. Next a number of Iterative phases follow, i.e. Functional Model, Design & Build and Implementation phases.The picture also mentions a number of rules and issues that are not included in the model, but that are important for this meta-model. First there are the rules that concerns the behavior of the ‘’Flows’’. These rules restrict the freedom of the flows so that they correspond to the ‘’Phase’’ transitions within DSDM. Next to the rules a number of important issues are addressed that ensure that the DSDM project life-cycle is guaranteed.
Comparison to other IS Development Methods
Over the years a great number of Information System Development methods have been developed and applied, divided in Structured Methods, RAD methods and Object-Oriented Methods. Many of these methods show similarities to each other and also to DSDM. For example eXtreme Programming(XP) also has an iterative approach to IS development with extensive user involvement.
Rational Unified Processis a method that probably has the most in common with DSDM in that it is also a dynamic form of Information System Development. Again the iterative approach is used in this development method.
Like XP and RUP there are many other development methods that show similarities to DSDM, but DSDM does distinguish itself from these methods in a number of ways. "First there is the fact that it provides a tool and technique independent framework. This allows users to fill in the specific steps of the process with their own techniques and software aids of choice. Another unique feature is the fact that the variables in the development are not time/resources," but the requirements. This approach ensures the main goals of DSDM, namely to stay within the deadline and the budget. And last there is the strong focus on communication between and the involvement of all the stakeholders in the system. Although this is addressed in other methods, DSDM strongly believes in commitment to the project to ensure a successful outcome.
* Rapid Application Development (RAD)
Agile software development
* Rational Unified Process (RUP)
Iterative and incremental development
Pareto principle(80/20 rule)
Structured Systems Analysis and Design Method(SSADM)
Lean software development
* Coleman and Verbruggen: "A quality software process for rapid application development", Software Quality Journal 7, p. 107-1222 (1998)
* Beynon-Davies and Williams: "The diffusion of information systems development methods", Journal of Strategic Information Systems 12 p. 29-46 (2003)
* Brinkkemper, Saeki and Harmsen: "Assembly Techniques for Method Engineering", Advanced Information Systems Engineering, Proceedings of CaiSE'98, Springer Verlag (1998)
* Abrahamsson, Salo, Ronkainen, Warsta "Agile Software Development Methods: Review and Analysis", VTT Publications 478, p. 61-68 (2002)
* Tuffs, Stapleton, West, Eason: "Inter-operability of DSDM with the Rational Unified Process", DSDM Consortium, Issue 1, p. 1-29 (1999)
* Rietmann: "DSDM in a bird’s eye view", DSDM Consortium, p. 3-8 (2001)
* [http://sdlc.bobstewart.com iSDLC] Dead link|date=May 2008 integrated Systems Development Life Cycle
* [http://www.dsdm.org The DSDM Consortium]
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