The V-Model XT
Overall Structure and Basic Concepts
1. The V – Model XT
The V – Model XT (VMXT) is a very special model which is very useful for planning, developing and analyzing software projects and models. It is currently used world-wide for the projects and models which are intended to achieve these following objectives.
- Minimize the Project Risks
The V – Model XT structures improve the transparency as well as the ability to plan project because it divides projects into many types and therefore each type will have a different way of approach and developing. Furthermore, the structures of VMXT is much more complex compare to others not only since it has many distinct types but also it has many different approaches and strategies regarding for each type.
- Improve and guarantee for the Product Quality
The VMXT inherits from its ancestor the ability to validate in the early stages. For any error that counters, the error should be fixed early to secure the quality. Thus, it is inevitable to say that the quality of the product would be ensured.
- Reduce the Entire Project Cost and System Life Cycle Cost
Thanks to the well – defined structures, all the stages from development, operation, testing to maintenance can be calculated and control by the model. This helps the stakeholders to define and re-define the project structure in their interest and also reduces the dependence from the acquirer on the supplier. Moreover, with the ability to track down error in early stage (as mentioned in 1.2), it can reduce a significant cost and also time.
- Improve the communication between different Stakeholders
Since the validation could be made during the verification stages, especially for the Safety Critical Systems, there will be a huge requirement of communication between the testing team and the developing team. Also, the acquirer and supplier have to communicate to agree on the system requirement.
Thus, the V – Model XT is a good model, especially for Safety Critical System, for guidance in processing, creating contract and can be used as the base communication.
2. Overall Structures of V – Model XT
Compared to the V – Model 97 (VM97), the V – Model XT structures and concepts is entirely different. Although the name of the model makes the readers feel like it is an updated version of it (but it is not), the reason behind it maybe comes from the fact that the VMXT keep the most of the VM97 advantages and in addition, reduces some of the VM97 drawbacks. VMXT can particularly solve the problems which regards to the project – specific in organization – specific. In other words, VMXT covers a larger range of system development projects than other old model, which is only suitable for some specific system projects) and is also suitable for many kinds of organization, from small one to big one.
During the project, using VMXT, this question always should be specified and answered:
“who has to do what and when?”
As already mentioned, there exists many kinds of software projects which is suitable to use VMXT, followed by different process modules and different strategies depend on the project type; the above question can be answer by the following steps:
What? – can be determined by selecting the right Project Type.
Who? – can be determined by selecting the right Process Modules.
When? – can be determined by selecting the right Project Execution Strategy.
3. Components of The V – Model XT
- Project Type
- Based on two main characteristics of the project which are Subject of the project and Project Role, there exists 4 product types definition in the V-Model XT:
- System Development Project of an Acquirer.
- System Development Project of a Supplier.
- System Development Project of a Supplier with the Acquirer.
- Introduction and Maintenance of an Organization – Specific Process Model.
- This is a crucial step that firstly have to be done in the V – Model XT.
Figure 1: The project types’ disparities in terms of characteristics
- Process Modules
- A Process Module is a concrete task which may occur within the scope of that Project. These modules are based on one another.
- Process Module is a huge package which contains:
- Work product: represent the part “what” of the module, including all the results, documents, source codes physical components, relating protocols, etc.
- Activities: represent the part “how” of the module.
- Roles: represent the part “who” (will do that activity) of the module.
Figure 2: A sample structure of Process Module and its components
- For each specific Project Type, there will be given a set of Process Modules predefined. Also, there exists some modules which are used in all Project Types, these are call mandatory Process Modules and together they are V – Model XT Core.
- Project Execution Strategies
- Since a system development project is more than often a complex one, then its execution is usually complex too. Therefore, to be able to plan and control all the process of the project, we need a strategy to order these processes and keep track on the plan so that we can decide the right path for our project. That is what the strategy do in the V- Model XT.
- For every Product Type, there exists a certain set of Strategies, which will differ based on the product expectation from the Stakeholders.
- Each Strategy includes what is called a subset of decision points and these points are arranged in order. Decision points can be known as the “milestone in the project sequence, where the current stage of the process is evaluated” (The V-Model XT Fundamentals 15).
Figure 3.a: All the decision gates in the V-Model XT version 1.3
Figure 3.b: The decision gates for Project of the Acquirer
Figure 3.c: The decision gates for Project of the Supplier
4. Basis Concepts of the V – Model XT
So far, we have had a look at the overall structure as well as all the main components of it. Now is the time to attach those components together and make them works.
- Choosing the right components
Obviously, it is inevitable to say that:
- There exist dependencies between Process Modules as well as Project Execution Strategies and Project Types.
- The Role, Activity and Work product are encapsulated in Process Modules whereas Decision Points are ordered in Strategies.
Therefore, it is necessary that first we need to find the right type of our project by knowing its characteristics. Then the rest of the jobs, using all the mapping and listing that have already given in the VMXT specification file, we can make a plan and start our project development .
Figure 4: Model of the relations between components
- XT stands for “extended tailoring”:
- ‘Tailoring’ comes from the Latin word ‘taliare’ which means to cut. Nowadays, this word is often used for describe a job of a tailor for making luxury clothes which is fixed and satisfied the customer. From that perspective view, it is not difficult to understand the most important concepts of the V – Model XT at all. Andreas Rausch and his teams have stated that the tailoring process “enables the V-Modell XT can be trimmed in order to fit a specific project so that all necessary products have to be created and no unnecessary activities are carried out.” (The V-Modell XT Applied – Model Driven and Document Centric Development, 4). Basically, based on the project characteristics, the model will be analyzed and specified by defining the right Type, selecting process modules and using a suitable strategy.
Figure 5: Tailoring mechanism
- Also, it is necessary to remind that this model, VMXT, does not entirely belong to neither linear model (e.g. Waterfall model, V – Model 97) nor agile model (Extreme Programming XP, SCRUM). After a quick discussion with my lecturer, we come to a conclusion that this is a model, to be precise, will choose whether the given project should use the linear model or agile model.
The V – Model XT is a model that works well for development a project which has the constraints about time, budget and the most important features: the project has to have the specified functionality. This model has a complex structure of components, including Project Types, Process Modules, Project Execution Strategies. These components are connected with others and with the ‘extended tailoring’ provide a new methodically way to develop system and project.
Pressman, Roger S.: Software Engineering: A Practitioner’s Approach, 8th Edition. McGraw-Hill 2014, New York, NY, U.S.A. ISBN 0-07-301933-X.
Birowicz, Ulrich: Evaluating Standard Software with V-Modell XT – A Case Study. 28th September, 2005.
Die Beauftragte der Bundesregierung für Informationstechnik: V – Modell XT Bund (Basis V – Modell XT 1.4). 2013, Germany.
Weber, Wolfgang: Does the usage of Development Processes like V-Model-XT or Rational Unified Process imply a good rating in Models like SPICE and CMMI? University of Applied Science, Darmstadt, Germany.
Aßmann, Uwe: Ablauforganisation mit Vorgehensmodellen. 2013, Dresden, Germany.
Rausch, Bartelt, Ternité & Kuhrmann: The V-Modell XT Applied – Model-Driven and Document-Centric Development. Technische Universität Kaiserslautern, Kaiserslautern, Germany.
Mark Hoffman & Ted Beaumont:Application Development: Managing the Project Life Cycle, Mc Press, ISBN 1-883884-45-4
Appendix: The V – Model Development Timeline
- 1986, the concept of V-Model was first developed by the Federal Office for Defense Technology in Germany.
- 1992, the first version was completed but many implementations were required.
- 1997, the updated V-Model was published as standard for all civil and federal agencies.
- 2004, the version of V-Model XT was completed.
- 2009, V-Model XT Version 1.3
- 2011, V-Model XT Version 1.4