Overview of DSDM : Phases of DSDM life-cycle

5 phases of DSDM lifecycle

phases of DSDM life-cycle

Pre-project

The pre-project phase ensures that only right projects are started and that they are set up correctly. Once it has been determined that a project is to go ahead, funding is available, etc., the initial project planning for the feasibility study is done. Then the project proper begins with the feasibility study.

The feasibility and business studies are done sequentially. They set the ground rules for the rest of development, which is iterative and incremental and therefore they must be completed before any further work is carried out on a given projects

Feasibility study

In this phase the problem is defined and the technical feasibility of the desired application is verified. Apart from these routine tasks, it is also checked whether the application is suitable for Rapid Application Development (RAD) approach or not. Only if the RAD is found as a justified approach for the desired system, the development continues.

Business study

In this phase the overall business study of the desired system is done. The business requirements are specified at a high level and the information requirements out of the system are identified. Once this is done, the basic architectural framework of the desired system is prepared. The team researches the business aspects of the project.

  • Does it make good business sense?
  • Who are the participants and interested parties?
  • What is the best work plan? What is needed to:
    1. Build it
    2. Test it
    3. Deploy it
    4. Support it?
  • What technologies will we be using to build and deploy it?

The systems designed using Rapid Application Development (RAD) should be highly maintainable, as they are based on the incremental development process. The maintainability level of the system is also identified here so as to set the standards for quality control activities throughout the development process.

Functional Model Iteration

This is one of the two iterative phases of the life cycle. The main focus in this phase is on building the prototype iteratively and getting it reviewed from the users to bring out the requirements of the desired system. The prototype is improved through demonstration to the user, taking the feedback and incorporating the changes.Prototyping follows these steps:

  • Investigate
  • Refine
  • Consolidate

This cycle is repeated generally twice or thrice until a part of functional model is agreed upon. The end product of this phase is a functional model consisting of analysis model and some software components containing the major functionality

Design and Build Iteration

This phase stresses upon ensuring that the prototypes are satisfactorily and properly engineered to suit their operational environment. The software components designed during the functional modeling are further refined till they achieve a satisfactory standard. The product of this phase is a tested system ready for implementation.

There is no clear line between these two phases and there may be cases where while some component has flown from the functional modeling to the design and build modeling while the other component has not yet been started. The two phases, as a result, may simultaneously continue.

Implementation

Implementation is the last and final development stage in this methodology. In this phase the users are trained and the system is actually put into the operational environment. At the end of this phase, there are four possibilities, as depicted by figure :

  • Everything was delivered as per the user demand, so no further development required.
  • A new functional area was discovered, so return to business study phase and repeat the whole process
  • A less essential part of the project was missed out due to time constraint and so development returns to the functional model iteration.
  • Some non-functional requirement was not satisfied, so development returns to the design and build iterations phase.

Dynamic System Development Method (DSDM) assumes that all previous steps may be revisited as part of its iterative approach. Therefore, the current step need be completed only enough to move to the next step, since it can be finished in a later iteration. This premise is that the business requirements will probably change anyway as understanding increases, so any further work would have been wasted.

Post-Project – Maintenance

After the product is created, maintenance will inevitably need to be performed. This maintenance is generally done in a cycle similar to the one used to develop the product.

According to this approach, the time is taken as a constraint i.e. the time is fixed, resources are fixed while the requirements are allowed to change. This does not follow the fundamental assumption of making a perfect system the first time, but provides a usable and useful 80% of the desired system in 20% of the total development time. This approach has proved to be very useful under time constraints and varying requirements.

Nine Principles of DSDM -Detail

Nine Principles of DSDM -Lite Version

Source

Dynamic System Development Method (DSDM)

What is DSDM?

DSDM is a framework based on best practice and lessons learnt since the early 1990’s by DSDM Consortium members. It is another approach to system development, which, as the name suggests, develops the system dynamically. It is independent of tools, in that it can be used with both structured analysis and design approach or object-oriented approach.

The Dynamic System Development Method (DSDM) is dynamic as it is a Rapid Application Development method that uses incremental prototyping. DSDM is particularly useful for the systems to be developed in short time span and where the requirements cannot be frozen at the start of the application building. Whatever requirements are known at a time, design for them is prepared and design is developed and incorporated into system. In Dynamic System Development Method (DSDM), analysis, design and development phase can overlap. Like at one time some people will be working on some new requirements while some will be developing something for the system. In Dynamic System Development Method (DSDM), requirements evolve with time.

DSDM focuses on delivery of the business solution, rather than just team activity. It makes steps to ensure the feasibility and business sense of a project before it is created. It stresses cooperation and collaboration between all interested parties. DSDM makes heavy use of prototyping to make sure interested parties have a clear picture of all aspects of the system.

Background of DSDM

Business are putting increasing pressure on their IT suppliers to deliver better systems, faster and cheaper. In today’s rapidly changing world, they are no longer able to wait for years for a system to be provided: the business may have changed radically during the years of development. It is imperative to find a different way of building IT systems. The technology that is now available to developers allows for more speedy production of system but the answer lies not only in the use of tools. The whole process needs to change. The classical, waterfall life-cycle does not take full advantage of modern technology and does not facilitate the change that is inherent in all systems development. It has been around for about 40 years and is basically the solution to an old problem -that of not having a full understanding of the problem to be solved and not having a coherent approach to solving the problem before starting to code a solution.

The waterfall approach of a strict sequence of stages has been seen to be flawed for many years now.Several attempts have been made to move away from it. including Barry Boehm’s iterative style of development using a spiral model of planning, risk analysis, engineering, and customer evaluation. Though excellent, the spiral model did not achieve the penetration into IT practices that it deserved. The emergence in recent years of many ‘Agile’ methods proves the need for a different approach. While some, such as Extreme Programming, have gained wide acceptance they do not cover all aspects of a project and can leave an organization confused as to how to integrate the many solution on offer. This provides one explanation for the less than optimal acceptance of agility as the way forward by the majority of IT solution providers. Another could be that, until recently there has been sufficient pressure from their customers.

In the early 1990s, the IT industry had become increasingly aware of Rapid Application Development following James Martin’s book Rapid Application Development, which gave some excellent pointers as to how to make the concept work, but did not provide the total solution, There are many tools on the market, but to use them often meant buying the vendor’s process as well. the founding members of the DSDM Consortium saw this as a block to the growth of successful and fast solution delivery.

The Consortium was inaugurated in January 1994 with the aim of producing a public domain, commonly agreed method which would be tool-independent. Ed Holt who chaired the Consortium for the first two years said that every organization that bought a RAD tool really needed a new process. DSDM aims to provide that process for building and maintaining systems that meet tight time constraints in a controlled project environment. The Consortium had 17 founder who resented a mix of organizations that remains today: large IT vendors, smaller tool vendors, and user organizations of all sizes.The Consortium now has hundreds of members with established regional consortia in North America, Benelux, Sweden , France and Denmark with interest growing in other countries, such as Australia India And China.

During 1994, the Consortium’s Technical Work Group put together the process and produced guidance material based on the experience and best practies of Consortium members. a few components of the framework were original ideas from experts in particular areas, but most of them were tried and tested -but they had never been brought together as a cohesive approach.

Why DSDM more rapid than the Waterfall ?

DSDM produces industrial strength systems that meet users’ need and are fully extendible and maintainable over long periods of time -they are not one-off or throwaway. In business  terms, they the exact peer of good system developed by the waterfall approach, but take a lot less time to develop.

There are two main reasons. Less is actually done. There is much less time spent in briefing people, and bringing them repeatedly up to speed. Little time is lost through task-switching by users or developers. Most importantly of all, only the features that are needed are actually developed.

The second reason is that problems, misunderstanding and false directions are identified and corrected early, so avoiding the massive rewrites often required late in waterfall projects. This has a further benefit. The resultant code developed under DSDM is consistent and of a piece, whereas waterfall code, by the end of the projects, is often already patched and out of synchrony with its documentation. The result is that DSDM=delivered code is also easier to maintain.

 When to use DSDM?

DSDM is not the panacea to all project ills that developers are often promised. There are classes of system to which the framework is most easily applied and these are the areas which an organization which is less experienced in agile development should focus on to begin with -unless of course the pressure to deliver is so great that an ‘unsuitable’ project must be tackled before the organization is mature in its use of the an agile approach, and DSDM is particular. The framework has been used in a wide variety of projects in a diverse set of organizations. It is difficult to say that the framework should never be used for a particular sort of application.

The main questions to ask when deciding on the appropriateness of a proposed system to DSDM development are:

  1. Is the functionality going to be reasonably visible at the user interface? :- Of course the use interface includes reports as well as screens or indeed any other way of showing the end-user what is happening inside the system. If users are to be involved throughout the development process, they must be able to verify that the software is performing the right actions through prototyping, without having to understand the technicalities of what is happening behind the user interface.
  2. Can you clearly identify all classes of end-users? :-It is essential to involve users within the project who can represent all of the potential end-user population. This has caused some concern when developing systems for widely disparate or geographically dispersed populations. The important thing is to ensure that you can obtain complete coverage of all relevant user views with on the development team. Otherwise there is a danger of driving the development in a skewed direction. Moreover the review process of sending out documents for a matter of weeks to a wide user group is very often not feasible on a DSDM project. Such reviews limit the chances of delivering on time.
  3. Is the application computationally complex? :-This is possible one of the hardest questions to answer. What is complex for one organization is simple for another. A lot will depend on what is available in terms of the building blocks to the development team. The important thing is not to develop too much complex functionality from scratch. This question is closely linked to the first question about the visibility of functionality. For instance, if the system is performing complex actuarial calculations, this could render the project difficult for DSDM. On the other hand, if the calculation processes have been used in previous systems and are tried and tested, the actuaries will trust what is presented to them.
  4. Is the application potentially large? :- DSDM has been used and is being used to produce very large systems, but in every case it has been possible to develop the functionality in fairly discrete chunks. There are several DSDM projects in progress at the time of writing that have a development period of two to three years. This could be viewed as not being rapid development, but increments will be delivered at regular intervals rather waiting until everything is complete before the system is put into operation. If the system is large and there is no possibility of incremental delivery, i.e. everything has to be delivered in a matter of months for the system to be useful, them it must be possible to break down the work for development by parallel teams.
  5. Is the project really time-constrained? :- It is all too easy for business management to say that a system must be delivered by a certain date when they don’t really mean it. This is potentially disastrous for the project. It means that whole the developers are geared up to follow the DSDM guidance; the end-user participation at all levels is not as forthcoming as it should be. At best this is frustrating. At worst, the project goes in the wrong direction because the drive from users is not there and developers start making assumptions about what is needed in order to keep active.
  6. Are the requirements flexible and only specified at a high level?:-This could be reworded as ‘Do you have complete understanding of everything that must be delivered?’ Whatever the project, the answer is just about always ‘No!’ but, for DSDM to work successfully, the level of detailed understanding at the outset of the project should be lower than is the norm.The use of prototyping with knowledge users to elicit requirements as you go is fundamental to the approach. If everything is understood and all the detailed requirements have been agreed and fixed before the software builders come on the scene, major benefits of DSDM will not be achieved, such as building the right system rather than what was originally requested.Also, if the requirements are inflexible, it will not be easy to negotiate what can be left out if the project deadline is approaching and a great deal of work remains to be done.

Sort description of phases of DSDM life-cycle

Nine Principles of DSDM -Detail

Nine Principles of DSDM -Lite Version

 

Source

 

Advantages and Disadvantages of Rapid Application Development (RAD)

Advantages of RAD Software Development
  • The time required to develop the software is drastically reduced due to a reduced requirement analysis business requirements documentation and software requirement specification) and planning stage.
  • All the software prototypes produced can be kept in a repository for future use. The re-usability of the components also enhances the speediness of the process of software development.
  • It is much easier for a project manager to be accurate in estimating project costs which of course means that project cost controls are easier to implement and manage as well.
  • It is a big cost saver in terms of project budget as well as project time and cost due to re-usability of the prototypes.
  • If a component is being picked for the repository, it is already tested and hence need not be tested again. This helps in saving time required for testing.
  • The project management requirements are collected in a dynamic manner. Every time there is a prototype ready, requirements are studied and matched. If there are any additional requirements, these are then included in the next prototype built.
  • There is a strong and continuous participation of the project sponsor who keeps giving feedback in the whole process. Hence the end user satisfaction level is higher when the end result is produced.
  • It promotes better documentation through written test cases.
Disadvantages of RAD Software Development
  • This method may not be useful for large, unique or highly complex projects
  • This method cannot be a success if the team is not sufficiently motivated and nor is unable to work cohesively together.
  • Success depends on the extremely high technical skills of the developers.
  • There are times when the team ignores necessary quality parameters such as consistency, reliability and standardization. Hence this can make project quality management hard to implement during the project management life cycle

Source

General Characteristics of Rapid Application Development (RAD)

Rapid Application Development Methodology

Incremental development

An important element of the philosophy of RAD is the belief that not all a system’s requirements can necessarily be identified and specified in advance. Some requirements will only emerge when the users see and experience the system in use, others may not emerge even then, particularly complex ones. Requirements are also never seen as complete but evolve and change over time with changing circumstances . Therefore, trying fully to specify a system completely in advance is not only a waste of time but often impossible. So why attempt to do it? RAD starts with a high-level, rather imprecise list of requirements, which are refined and changed during the process, typically using toolsets . RAD identifies the easy, obvious requirements and, in conjunction with the 80/20 rule , just uses these as the starting point for a development, recognizing that future iterations and timeboxes (see below) will be able to handle the evolving requirements over time. Hough (1993) suggests using the technique of functional decomposition and each function identified and the requirements listed, but, he says,

the precise design specifications, technical issues, and other concerns should be deferred until the function is actually to be developed

Time-boxing

The system to be developed is divided up into a number of components or timeboxes that are developed separately. The most important requirements, and those with the largest potential benefit, are developed first and delivered as quickly as possible in the first time box. Some argue that no single component should take more than 90 days to develop, while others suggest a maximum of six months. Whichever timebox period is chosen, the point is that it is quick compared with the more traditional systems development timescale.

Systems development is sometimes argued to have three key elements. In tradi- tional development two are typically variable: time and resources (see Figure 6.3). In traditional development when projects are in difficulty, either the delivery time is extended or more resources are allocated or both but the functionality is treated as fixed. In RAD the opposite applies, resources and time are regarded as fixed (allocating more resources is viewed as counterproductive although this does sometimes happen), and so that only leaves functionality as a variable. So, under pressure and when projects are in difficulty, time and resources remain constant but the functionality is reduced.

Traditional development -time and resources

Figure 1.1: Traditional development -time and resources

RAD compartmentalizes the development and delivers quickly and often. This provides the business and the users with a quick, but it is hoped, useful part of the system in a refreshingly short timescale. The system at this stage is probably quite limited in relation to the total requirements, but at least something has been delivered. This rapid delivery of the most important requirements also helps to build credibility and enthusiasm from the users and the business. Often for the first time they experience a system that is delivered on time. This is radically different from the conventional delivery mode of most methodologies which is a long development period of often two to three years followed by the implementation of the complete system. The benefits of RAD development is that users trade off unnecessary (or at least initially unnecessary) requirements and wish lists (i.e. features that it would be ‘nice to have’ in an ideal world) for speed of development. This also has the benefit that, if requirements change over time, the total system has not been completed and each timebox can accommodate the changes that become necessary as requirements change and evolve during the previous timebox. It also has the advantage that the users become experienced with using and working with the system and learn what they really require from the early features that are implemented.

Comparison of timebox development and traditional development

Figure 1.2: Comparison of timebox development and traditional development

Figure 1.2 illustrates three chunks of development and, although the overall time to achieve the full implementation could be the same as with a .traditional development, the likelihood is that the system actually developed at the end of the three timeboxes will be radically different from that developed at the end of one large chunk as a result of the learning and evolving processes which leads to change being made to each specification at the beginning of each timebox.

Some RAD proponents argue that, if the system cannot be divided into 90 day timeboxes, then it should not be undertaken at all. Obviously such an approach requires a radically different development culture from that required for traditional or formalized methodologies. The focus is on speed of delivery, the identification of the absolutely essential requirements, implementation as a learning vehicle, and the expectation that the requirements will change in the next timebox. Clearly such radical changes are unlikely to be achieved using conventional techniques.

Once the duration of the timebox has been decided it is imperative that the system is delivered at the end of it without slippage, as timeboxes are fixed. So how is this achieved? Well, first, by hard work and long hours and, secondly, by the use of the other RAD techniques discussed below. But also if slippage is experienced during development of a timebox then the requirements are reduced still further (i.e. some of the things that the system was going to do will be jettisoned).

The Pareto principle

This is essentially the 80/20 rule and is thought to apply to requirements. The belief of RAD proponents is that around 80 per cent of a systems’ functionality can be delivered with around 20 per cent of the effort needed to complete 100 per cent of the requirements. This means that it is the last, and probably most complex, 20 per cent of requirements that take most of the effort and time. Thus why do it? – just choose as much of the 80 per cent to deliver as possible in the timebox, or at least the first timebox. The rest, if it proves necessary, can be delivered in subsequent time boxes.

MoSCoW rules

In RAD the requirements of a project are prioritized using what is termed the MoSCoW Rules:

  •  M = ‘the Must Haves’. Without these features the project is not viable (i.e. these are the minimum critical success factors fundamental to the project’s success).
  • S = ‘the Should Haves’. To gain maximum benefit these features will be delivered but the project’s success does not rely on them.
  • C = ‘the Could Haves’. If time and resources allow these features will be delivered but they can easily be left out without impacting on the project.
  • W = ‘the Won’t Haves’. These features will not be delivered. They can be left out and possibly, although not necessarily, be done in a later timebox.

The MoSCoW rules ensure that a critical examination is made of requirements and that no ‘wish lists’ are made by users. All requirements have to be justified and categorized. Normally in a timebox all the ‘must haves’ and at least some of the ‘should haves’ and a few of the ‘could haves’ would be included. Of course, as has been mentioned, under pressure during the development the ‘could haves’ may well be dropped and even possibly the ‘should haves’ as well.

JAD workshops

RAD requires high levels of participation from all stakeholders in a project as a point of principle and achieves this partly through the JAD workshop. JAD (Joint Application Development) is a facilitated meeting designed to overcome the problems of traditional requirements gathering (see Section 16.2), in particular interviewing users. It overcomes the long time that the cycle of interviews take by getting all the relevant people together in a short period to hammer out decisions. Normally in the context of RAD, a JAD workshop will occur early on in the development processto help establish and agree the initial requirements, the length of the timebox, what should be included and what excluded from the timebox, and most importantly to manage expectations and gain commitment from the stakeholders. Sometimes a subsequent JAD workshop is used to firm up on the details of the initial requirements, etc. In some RAD approaches the whole process is driven by a series of JAD meetings that occur throughout the timebox.

The fourth element is the presence of an executive sponsor. This is the person who wants the system (or whatever the focus of the meeting is), is committed to achieving it and is prepared to fund it. This person is usually a senior executive who understands and believes in the JAD approach and who can overcome the bureaucracy and politics that tend to get in the way of fast decision making that usually bedevils traditional meetings

Prototyping

Prototyping is an important part of RAD and is used to help establish the user requirements and in some cases the prototype evolves to become the system itself. Prototyping ;helps speed up the process of eliciting requirements, and speed is obviously important in RAD, but it also fits the RAD view of evolving requirements and users not knowing exactly what they want until they see or experience the system. Obviously the prototype is very helpful in this respect.

Sponsor and Champion

Having a committed sponsor and a champion of the systems is an important requirement for RAD and for its success. We have discussed the sponsor above. A champion is someone, often at a lower level of seniority, who is also committed to the project, who understands and believes in RAD, and is prepared to drive the project forward and overcome some of the bureaucracy and politics.

Toolsets

RAD usually adopts, although not necessarily, the use of toolsets to help speed up the process and improve productivity. In general it is usually argued that the routine and time-consurning tasks can be automated as well as using available tools for change control, configuration management, and even code reuse. Reuse of code is another way that RAD speeds the development process. However, it is not just about speed but also quality because existing code or modules have usually already been well tested, not just in development, but in real use. RAD searches for shortcuts and reuses code, maybe clones existing code and modifies it, or utilizes commercial packages, etc. where applicable. This may be code within the organization or bought from outside. Sometimes more than just a little piece of code is used; for example, complete applications may be used and the developers use this as the basis of the new system and change the interface to produce the desired results. Many ‘new’  e-commerce or Internet applications have been developed in this way using the legacy systems and then providing a new ‘umbrella’ set of applications and user interfaces on top. The idea is to leverage existing code, systems, experience, etc.

Specific RAD productivity tools have been around for some time and are developing fast, and existing tools and languages are being enhanced for RAD, particularly for rapid development of Internet and e-business based applications.

Source

  • David Avison & Guy Fitzgerald, 2006. Rapid application development (RAD). In David Avison & Guy Fitzgerald Information Systems Development. 4th ed. Pearson Education Limitied. Ch. 7. pp.128-132.ISBN-13 978-0-07-711417-6

Rapid Application Development Methodology

A method of developing information systems which users prototyping to achieve user involvement and faster development compared to traditional methodologies such as SSADM.
Professor Clifford Kettemborough of Whitehead College, University of Redlands,
defines

Rapid Application Development as an approach to building computer
systems which combines Computer-Assisted Software Engineering (CASE) tools and techniques, user-driven prototyping, and stringent project delivery time limits into a potent, tested, reliable formula for top-notch quality and productivity. RAD drastically raises the quality of finished systems while reducing the time it takes to build them.

Online Knowledge defines

Rapid Application Development as a methodology that
enables organizations to develop strategically important systems faster while reducing
development costs and maintaining quality. This is achieved by using a series of
proven application development techniques, within a well-defined methodology.

History

Rapid application development is a term originally used to describe a software development process introduced by James Martin in 1991. Martin’s methodology involves iterative development and the construction ofprototypes. More recently, the term and its acronym have come to be used in a broader, general sense that encompasses a variety of methods aimed at speeding application development, such as the use of software frameworks of varied types, such as web application frameworks.

RAD vs. Waterfall

In the 1970s and 1980s, several sequential software engineering processes were developed that regarded application development as flowing steadily downward through the different phases of the development process.

Traditional development vs. Rapid Application Development

Traditional development vs. Rapid Application Development

The first description of such a waterfall model is often cited in an article published in 1970 by Winston W. Royce2. However, in this article, Royce presented the model as an example of a flawed, non-working approach. “Waterfall” has in later years become a common term to criticize traditional software development practices. The problem with most waterfall models is the fact that it relies on a methodical requirements analysis phase alone to identify all critical requirements for the application. There is ample evidence that projects using a waterfall approach often fail to provide a useable end product; because projects often exceed their deadlines, the product either fails to meet all requirements or the requirements change during the protracted development phase.

There have been many responses to this problem from the 1980s to today, but almost all of those responses focus on the idea of developing systems in a short timeframe with small teams of highly skilled and motivated staff. It is the iteration step that solves the problems inherent to the inflexible approach of traditional software development.

Why was needed to invent RAD?

The evidence from project failures for projects in the 1980s and 1990s, as evidenced for example by the Standish Group Chaos report (1995), implies that traditional structured methodologies have a tendency to  deliver systems that arrives too late and therefore no longer meet their original requirements. Traditional methods can fail in a number of ways.

  • A gap of understanding between user and developers: Users tend to know less about what is possible and practical from the a technology perspective, while developers may be less aware of the underlying business decision -making issues which lie behind the systems development requirement.
  • Tendency of developers to isolate themselves from users: Historically, systems developers have been able to hide behind  a wall of jargon, thus rendering the user community at an immediate disadvantages when discussing IS/IT issues. While some jargon may be necessary if points are to be made succinctly, it is often used to obscure poor progress with a particular development project.  The tendency for isolation is enhanced by physical separation of some computer staff in their air-conditioned computer rooms. Developers might argue in their defence that users also have their own domain-specific jargon which adds to the problem of deciphering requirements.
  • Quality measured by closeness of product to specification: This is a fundamental difficultly – the observation that ‘ the system does exactly what the specification said it would so’  hides the fact that the system may still not deliver the information that the users need for decision-making purpose. The real focus should be on a comparison of the deliverables with the requirements, rather than of  deliverables  with a specification that was a reflection of a perceived need at a particular point in time.
  • Long development times: SSADM and the waterfall model will reveal that the process of analysis and design can be very laborious and time-consuming. Development times are not helped by the fact that and organization may be facing rapidly changing business conditions and requirements may similarly be changing. There is a real risk of the ‘moving goal-post’  of syndrome causing havoc with a traditional approach to systems development.
  • Business needs change during the development process: This is alluded to above. A method is needed where successive iterations in the development process are possible so that the latest requirements can be incorporated.
  • What users get isn’t necessarily what the want: The first a user may see of a new information system is at the testing or traning stage. At this point , it will be seen whether the system as delivered by the IS/IT professionals in what the user acually needs. An appropriate analogy here is the purchase of a house or car simply on the basis of discussions with an estate  or a garage agent  rather than by actually visiting the house or driving the car. It is unlikely that something purchased  in this way will result in a satisfied customer and there in no reason to suppose that information systems developed is a similar way will be any more successful.
Rapid Application Development Model

Rapid Application Development Model

Not only is there pressure from end-user management for faster systems development, IS/IT department themselves increasingly recognize the need to make more effective use of limited human resources within is their departments while at the same time quickly delivering systems that confer business benefits. All this is is a climate of rapid business change and therefore, rapidly changing information needs. Rapid Application Development (RAD) is a method possible solution to these problems and pressures.

Is RAD  appropriate for all projects?

The Rapid Application Development methodology was developed to respond to the need to deliver systems very fast. The RAD approach is not appropriate to all projects – an air traffic control system based on RAD would not instill much confidence. Project scope, size and circumstances all determine the success of a RAD approach. The following categorize indicates suitability for a RAD approach:

Project Scope
Suitable for RAD – Focused scope where the business objectives are well defined and narrow.
Unsuitable for RAD – Broad scope where the business objectives are obscure or broad.

Project Data
Suitable for RAD – Data for the project already exists (completely or in part). The project largely comprises analysis or reporting of the data.
Unsuitable for RAD – Complex and voluminous data must be analyzed, designed and created within the scope of the project.

Project Decisions
Suitable for RAD – Decisions can be made by a small number of people who are available and preferably co-located.
Unsuitable for RAD – Many people must be involved in the decisions on the project, the decision makers are not available on a timely basis or they are geographically dispersed

Project Team
Suitable for RAD – The project team is small (preferably six people or less).
Unsuitable for RAD – The project team is large or there are multiple teams whose work needs to be coordinated.

Project Technical Architecture
Suitable for RAD – The technical architecture is defined and clear and the key technology components are in place and tested.
Unsuitable for RAD – The technical architecture is unclear and much of the technology will be used for the first time within the project.

Project Technical Requirements
Suitable for RAD – Technical requirements (response times, throughput, database sizes, etc.) are reasonable and well within the capabilities of the technology being used. In fact targeted performance should be less than 70% of the published limits of the technologies.
Unsuitable for RAD – Technical requirements are tight for the equipment to be used.

General Characteristics of Rapid Application Development (RAD)

   Sources

Running prototype demonstrations in DSDM

In order to get the best value out of prototype demonstrations, the guidelines below should be followed.

The demonstrators should prepare the audience for any prototype demonstration session. The objectives of the session should be clearly stated together with the known limitations of what will be seen. It can be too easy to assume that, since one or two users have been involved in the development of a prototype, the rest of the user community are as knowledgeable about what is going on. Indeed, the Ambassador Users will talk to their colleagues but this communication channel should not be totally relied upon until working software has been demonstrated to the wider user population, as it is often difficult to explain what has not been seen – the reason why DSDM is the way it is.

During the session, discussion should be encouraged. Putting the prototype through its paces at such a speed that the users cannot see what may be expected of them in the future is worse than useless. The development team may come away from the session feeling reassured that they are following the right track, whereas all that has happened is that any comments have been stifled.

The Scribe should record all comments made during the demonstration. Otherwise, since the focus of the developers  and the users will be on the behaviour of the prototype, some feedback may be forgotten.

Source:

Testing prototypes in DSDM

DSDM prototype serves two different roles:

  • it is a partial build of the system that will be delivered
  • it is a technique for gathering information to clarify functional or non-functional requirements.
Different test criteria apply depending on the role the prototype is serving:
  • To the extent that the prototype represents part of the functionality of the final system, a test pass/fail can be based on whether or not the test result from the prototype matches an expected result based on the known  requirements.
  • To the extent that the prototype is intended to clarify requirements, the criterion for test success or failure is whether or not the prototype generates the expected information. This is exploratory. The expected
    information cannot be predefined in the same way that an expected result can be. The test of the prototype is being used to expand the knowledge and understanding of the prototype builder. The test is successful if this
    is achieved in the area under investigation.

A single prototype may serve in both roles and therefore should be tested against both criteria.In the Functional Model and Design and Build Iteration phases, prototyping generally iterates up to three times in line with the timeboxing process.  The prototypes that are produced can fall within any one of four categories. Prototypes of all categories can be tested against a mixture of “expected result” and “expected information” criteria.

This iterative lifecycle is summarised in the table below, which shows the categories of prototype and the type of testing criteria that will tend to apply at each iteration.

Iteration within Timebox
Prototype Category Investigation Refinement Consolidation
Business EI EI/ER ER
Usability EI EI/ER ER
Performance EI EI/ER ER
Capability EI EI/ER ER
Testing criteria for the categories of prototype (EI = Expected Information, ER = Expected Result)

Managing the prototyping process in DSDM

This section discusses a number of key issues that surface in the management of the prototyping process.

Managing iteration

There are several aspects that have to be managed in order to achieve successful passage through prototyping
activities. These are:

  • timeboxing
  • change control
  • configuration management
  • user involvement
  • quality assurance of products
  • learning from earlier iterations.

Strict adherence to timeboxes ensures that prototyping cycles are not allowed to lose their focus on delivering to the agreed priorities and that the quality of products is assessed within each timebox.

The procedures for change control must enable change to be introduced quickly and effectively. Over-prescriptive procedures will slow down development.

In order to be able to backtrack to a previous prototype, strong configuration management must be enforced. For instance, users may decide that a previous user interface was preferable to the current one or that the functionality is
progressing in the wrong direction to meet their most immediate business needs. In such circumstances, it must be possible to move backwards smoothly and for all developers to be sure of which version or variant is the current one.

While prototyping without user involvement is impossible, it is important that the users do not drive the development in the wrong direction through lack of knowledge outside their own sphere of activities. Senior user management must
ensure that a representative set of users is included in prototyping activities.
To ensure that prototyping progresses as fast as possible, it is important that the selected user representatives are available at all times when they are needed.
By keeping the team consistent throughout development, the team can learn from previous prototyping activity and so improve the quality of the products and the efficiency of working.
The number of iterations
As a general rule, it is recommended that three iterations be allowed – and that they are aligned to the timebox process:
  • investigation to see whether the right approach is being taken
  • refinement to build on the comments and feedback after the investigative prototype
  • consolidation to fully satisfy the objectives of the prototype.

This will mean three prototype cycles leading to a part of the Functional Model and three prototype cycles leading to a part of the Tested System. However, if the nature of the application and/or the technical environment mean that functional modelling and design and build merge then the number of prototypes will obviously be reduced. It is generally advisable to avoid more than three iterations since this can encourage a feeling that things can be left until later.

Collaboration and consensus

Prototyping requires collaboration and consensus between the developers and the users, as distinct from a contract negotiated at the start of the process, which can frequently be a source of confrontation between developers and users.

Choosing what to prototype

When producing the Development Plan, the project manager and the team decide where the categories of prototypes (and any combinations of them) are most appropriate, given the business and technical environment.

Horizontal vs. vertical approach

Having chosen the area to prototype, the DSDM team must first choose whether to build their prototypes in a horizontal or a vertical way. The choice is simply a way of slicing up the application, so any category of prototype may appear in a
horizontal or a vertical application slice.

With a horizontal approach the whole system is first built at a high level to check how it will cover the scope of the project. The detail is filled in later. With a vertical approach a section of the computer system is built incrementally until
it is fully understood, then the next section is started.

Both approaches have their advantages and disadvantages. If the whole concept of the system/business area is new then a horizontal approach may be safer. If the overall structure of the system is well understood but the detail is unclear then a vertical approach might be better. One advantage of the vertical approach is that it allows incremental deployment of subsystems for immediate business benefit. Generally, systems will be built using a combination of  horizontal and vertical approaches.

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Prototyping cycles in DSDM

Each of the development phases (the Functional Model and the Design and Build Iterations) contains iteration through
prototyping. There are basic controls that must be implemented in order to ensure the success of these activities.
These controls are built into a prototyping cycle and are aligned to the cycles within the timebox process.

A prototyping cycle passes through four stages:

  •  identify prototype
  • agree plan
  • create prototype
  • review prototype.
Identify prototype
Before embarking on building a prototype, what is to be prototyped must be clearly identified. This decision will be based on the relative priorities given to the functional and non-functional requirements. Having partitioned the application into possible prototypes, it should be made clear which are the essential parts of each prototype and which are “extras” through applying the MoSCoW rules. This will limit the scope of activity in each prototyping cycle and determine the priorities of the developers and users who are building the prototype.
The prototypes can be selected by various criteria: business area, basic processing required, the user groups, information accessed and the criticality of the processing to the final system.
The results of reviews from previous prototyping cycles provide valuable information when identifying the prototypes to be developed.

Acceptance criteria for the prototype should be defined in outline before any development takes place in order to lead the prototyping activity in the most useful direction.

Agree plan

The Development Plan in its schedule of timeboxes sets a limit on the time to be spent on each prototype. The team must agree the detailed plan for the current prototyping cycle. This includes prototyping the Must Haves first. Lesser parts will be dealt with if time is available.

The plan should not be allowed to slip unless significant problems arise, e.g. unexpected and dramatic changes in scope. However, such problems will probably require halting all activity temporarily while the project direction is
rethought.

It is important that the reasons for the time limit are clearly understood by the users. It is their priorities that will identify the essential components of a prototype. They must be made fully aware that asking for in-depth investigation of a particular area may mean that they have to decide what other area they can do without.

Create prototype

The prototypes are usually developed collaboratively with users. However later in development where issues such as performance are being addressed, the users will take a back seat.

Prototypes are not necessarily automated. For instance, early in development, a paper-based storyboard may be more cost-effective and flexible than a fully automated user interface to unexplored functionality. Both business and technical imperatives will drive the choice of prototyping medium.

Review prototype

Each prototype should be reviewed by the prototyping team (both developers and users) and other interested parties, where appropriate, (e.g. business analysts and senior user management) to ascertain:

  • which objectives it has met successfully
  • which areas will have to be included in later development
  • which missed areas can be safely postponed (or possibly incorporated in another project) in order to achieve the project’s timescales
  • the acceptability of what has been produced.

As well as verifying that the relevant quality criteria have been met, there are two major aims of the review:

  • to ensure that the development team are following the right track
  • to get the users at all levels to buy in to the completed and future work.
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Categories of prototypes as recommended by DSDM

Dynamic Systems Development Method (DSDM) is a framework for delivering business solutions that relies heavily upon prototyping as a core technique, and is itself ISO 9001 approved. DSDM uses the word ‘prototyping’ because that is the industry ‘standard’, but they are not truly prototypes: they are partial system components. A DSDM prototype is not ‘all done by mirrors’, but is built using the platform on which all the development work is done, and meeting all the required  standards. In other words, the prototypes are intended to be evolutionary {may be evolved horizontally (breadth then depth) }rather than throwaway {each section is built in detail with additional iterations detailing subsequent sections}: they will evolve into the delivered system. Of course, there will be occasions when it is better to throw something away and start again, but the aim at all times should be to build on what is there already.

Four categories of prototype are recommended by DSDM that are used at different stages of development, and have very different purpose. They are:

  • Business prototypes
  • Usability prototypes
  • Performance and capacity prototypes
  • Capability / design prototypes

While the purpose of each prototype category is different, it will often be the case that some combination of them will be used. For instance, a common combination is the business and usability prototype, but this approach should not be taken as a matter of course. If the functionality is at all complex, it may be better to get it right before worrying about the presentation aspects. Conversely, if there is no standard for user interface design, it is good idea to get some usability prototyping done first. The categories of prototype to be built in a timebox should be decided at its outset based on the aims of the timebox.

Business prototypes

  • Purpose:
    A business prototype demonstrates the developers’ understanding of the functional requirements. The developers can use this prototype to demonstrate to the users how the final system could work. This will enable the users to better formulate their real business requirements.
  • Description:
    A business prototype is designed only to demonstrate how the business processes are supported by the computer system. It is not designed to look good or to be particularly user-friendly: nor will secondary functionality, such as error checking, necessarily be implemented. It is very important that the users understand the purpose of demonstrating a business prototype.
  • How used:
    A business prototype enables the developers to demonstrate to the users their understanding of the key system requirements early in the project. This early prototype can then be evolved to cover more of the functionality and to incorporate non-functional aspects. Typically, the developer will use a scripted demonstration to ensure that the functionality is demonstrated to best effect. Any discrepancies between the developers’ understanding and the business requirements are noted.
  • Position in the project lifecycle :
    The first business prototype will be demonstrated as early as possible in the project lifecycle (possibly as early as the Feasibility Study, but no later than early in the Functional Model Iteration). This will confirm the right system is being built. First, the fundamental functionality of the system will be demonstrated. Later on, more detailed functional requirements can be demonstrated and/or other areas can be business prototyped.The final business prototype will clearly demonstrate to the users how the system will work. It may not look very pleasing, and have lots of missing functionality, but it will ensure the right system is being built.
Usability prototypes
  • Purpose: A usability prototype ensures the computer system will be as easy and intuitive to use as possible. Users should enjoyusing the system and it should be obvious how the system can be used. If this is done well, end-users will need less training before they can use the system effectively, while still having a good understanding of the full capabilities of the system.
  • Description:
    Well-designed computer systems are simple and straightforward, easy to learn and understand, and fun to use. It is impossible to achieve usability without trying the system out on the users. A usability prototype demonstrates how the user interacts with the system. It may not actually automate the business process. For example a form is displayed, the user adds data, but nothing is written to disk. The user can understand how to move around the system and how the  interface works.
  • How used:
    A user carries out a number of tasks using the prototype.  Any difficulties encountered by the user in achieving those tasks are noted so that the usability of the system can be improved.Contrast this with the business prototype where the developer will typically demonstrate the system, to show the functionality only. A business prototype may be rather user-unfriendly so it is better if the developer removes the need for a user to learn the interface.There is a danger of building a usability prototype that cannot be developed into the final system. Developers must take care not to create any unrealistic expectations.
  • Position in the project lifecycle:
    usability prototype may be built during either the Functional Model Iteration or the Design and Build Iteration, but there are many benefits in building it as early as possible. For a computer system to be easy to use, it must have a simple conceptual  model that the users can easily understand to help them move around the system.
    A usability prototype confirms that a good conceptual model has been chosen. If this is not done early on in the project and the model is wrong, it could adversely affect the design of the system. To reduce the risk of this, a high-level usability prototype should be built in the Functional Model Iteration or early on in the Design and Build Iteration. More detailed usability, such as the buttons in a window, can be designed later. If standards for the user interface are chosen early on, then all programs can be built to the agreed standard, reducing the need for rework. Having a stable installation Style Guide in place before prototyping commences on any project would help even more.In practice there are many benefits in combining the business and usability prototypes.
Performance and capacity prototypes
  • Purpose:
    A performance and/or capacity prototype ensures that the final computer system will be able to handle the full peak time workload required. While users may be involved, this category of prototype is typically for the benefit of the developers.
  • Description:
    This prototype deals with the non-functional aspects of the system, such as concurrent transaction volumes, data loading, overnight batch reports, and month end batch runs, as well as on-line screen performance. Checks will be made that the target system has enough resources to function adequately in the live environment, even when other systems are competing for machine resources.
  • How used:
    Performance and capacity prototypes are usually developed for the benefit of the developers to ensure the computer system can meet its desired performance requirements. A test scenario is set up and repeated while changing different aspects of the system to see how it performs. This process is best automated so that it is easily repeated, but it can be
    done manually where a group of users follow a script. The system is monitored to see where any “bottlenecks” occur.
  • Position in the project lifecycle:
    This category of prototype is typically used during Design and Build Iteration, after the required functionality has been determined. Often existing business prototypes will be used for performance testing. Sometimes early in the project design, the developers may be concerned as to whether a certain piece of functionality can be provided within the
    constraints of the machine/network environment. In this case, a performance and capacity prototype can be specially built to check where the limits might be. Such a prototype might look very different from the final system.
Capability/technique prototypes
  • Purpose:
    Developers often have a range of design options and sometimes a choice of tools to use. A capability/technique prototype tries out a particular design approach or tool to help in choosing between these options.
  • Description:
    This category of prototype is typically limited in functionality and is for the benefit of the developers only. The prototype demonstrates the capabilities and limitations of an approach, a technique or a tool to the developers.
  • How used:
    The developer builds a number of prototypes and weighs up the benefits of each technical approach.
  • Position in the project lifecycle:
    Although selection of a tool is usually made outside any one particular project, a tool capability prototype can be developed during the Feasibility Study to ensure that the potential technical approach will be soundly based. Later design capability/technique prototypes are created during the design phase of a project.Different designs or tools are used to build prototypes that represent the options available to the developer. Each prototype can then be assessed and the best approach, technique or tool selected.
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