# Hans van Vliet

Johannes Cornelis (Hans) van Vliet (born 12 September 1949) is a Dutch computer scientist and Professor Emeritus of Software Engineering at the Vrije Universiteit Amsterdam, known for his work in quantitative aspects of software engineering.

## Quotes

* Innovative e-business projects start with a design of the e-business model. We often encounter the view, in research as well as industry practice, that an e-business model is similar to a business process model, and so can be specified using UML activity diagrams or Petri nets. In this paper, we explain why this is a misunderstanding. The root cause is that a business model is not about process but about value exchanged between actors. Failure to make this separation of concerns leads to poor business decision-making and inadequate business requirements.
** Jaap Gordijn, Hans Akkermans, and Hans Van Vliet. "Business modelling is not process modelling." International Conference on Conceptual Modeling. Springer Berlin Heidelberg, 2000. Abstract

### Software Engineering: Principles and Practice, 2007

Hans van Vliet (2007) Software Engineering: Principles and Practice.
* Computer science is still a young field. The first computers were built in the mid 1940s, since when the field has developed tremendously. Applications from the early years of computerization can be characterized as follows: the programs were quite small, certainly when compared to those that are currently being constructed; they were written by one person; they were written and used by experts in the application area concerned. The problems to be solved were mostly of a technical nature, and the emphasis was on expressing known algorithms efficiently in some programming language. Input typically consisted of numerical data, read from such media as punched tape or punched cards. The output, also numeric, was printed on paper. Programs were run off-line. If the program contained errors, the programmer studied an octal or hexadecimal dump of memory. Sometimes, the execution of the program would be followed by binary reading machine registers at the console.
** p. 2
* Present-day applications are rather different in many respects. Present-day programs are often very large and are being developed by teams that collaborate over periods spanning several years. These teams may be scattered across the globe. The programmers are not the future users of the system they develop and they have no expert knowledge of the application area in question. The problems that are being tackled increasingly concern everyday life: automatic bank tellers, airline reservation, salary administration, electronic commerce, automotive systems, etc. Putting a man on the moon was not conceivable without computers.
** p. 2
* Software engineering concerns methods and techniques to develop large software systems. The engineering metaphor is used to emphasize a systematic approach to develop systems that satisfy organizational requirements and constraints.
** p. 2
* Almost 2000 years ago, the Roman architect Vitruvius recorded what makes a design good: durability (firmitas), utility (utilitas), and charm (venustas). These quality requirements still hold, for buildings as well as software systems. A well-designed system is easy to implement, is understandable and reliable, and allows for smooth evolution. Badly-designed systems may work at first, but they are hard to maintain, difficult to test, and unreliable.
** p. 279

## External links

* prof. dr. J.C. (Hans) van Vliet at Vrije Universiteit, Amsterdam