Going Back Home by Ivar Jacobson

July 3, 2004

After three days in St. Petersburg I am now on my way to the city where I grew up and graduated from high school. The city is Ystad located in the very south of Sweden at the Baltic Sea. Every year I spend a week in Ystad to meet old friends, friends I have had since I was 7-18 years old.

To my surprise there are not yet any major software conferences in Russia. Conferences are organized by universities or by international companies like SUN, Microsoft, etc. I gave a talk at the 5th international scientific and technical conference and got a good impression of what people worked with and what was presented. Then I met with academic leaders with a strong network in the software industry. I spent a day at St. Petersburg State University as a guest of Professor Andrey Terekhov.

That day turned out to be very interesting. For many years I have been wanting to develop process and tools to reengineer old software systems to become modern component based software, modeled with UML and implemented on modern platforms such as J2EE or .NET. Andrey told me that he had been working with a company in the US that sells tools and services to reengineer from the bottom and up. I know the company very well. In fact, a few years ago, they offered me to become a member of their advisory board. And now I met the guy who developed their tools.

The reason I didn’t accept the offer was that I didn’t see that their design would be generic enough. They had their own modelling technique, their own process and their own tools. My approach is the one I wrote about 1991 in my OOPSLA’91 paper on Reengineering Old Systems to an Object-Oriented Architecture. However, I liked their low level reverse engineering tools. And these tools were developed by Andrey and his company. I think there is a huge demand to reengineer legacy systems, particularly those written in COBOL or PL/1. I have many customers that would be willing to invest in such tools. I am now thinking about if and how to do this. Thus, the meeting with Professor Andrey Terekhov and his team was really refreshing.

During my stay in St. Petersburg, I enjoyed sightseeing and good restaurants. Elena Ivanova arranged my whole visit and she and her son were great guides. Of course, the Ermitage was very interesting. Also just walking around in the city during the beautiful White Nights and along the Neva River was very relaxing and romantic. And I love Beluga caviar. I had caviar with small vodka every night, and carried home as much as you are allowed. The price for 213 g top quality caviar was just 50 USD. At home I would have had to pay more than 1,000 USD. Maybe we are in the wrong business?  

Looking Back on Aspects by Ivar Jacobson

June 6, 2004

Often I am asked which my favourite country is. In addition to Sweden, where I grew up and have family, I have many favourite countries. Most countries have something that makes me feel happy and at home. Singapore is certainly one of them.

Last Thursday I held a seminar in Singapore for more than 200 persons and launched my latest adventure – the forming of a new company, Ivar Jacobson Pte Ltd. We will help organizations to implement the best practices of the unified process. We will also expand the set of best practices, not just help with the existing ones. For instance we will train and mentor organizations in aspect-oriented software development and active software development (using intelligent agents).

One of the best practices is about aspects. The first time I heard the term aspect-oriented programming was back in 1997. I immediately saw it as an interesting technology, but at the time I couldn’t take a serious look at. I was working on the first version of UML, I was working on getting RUP right and I was initiating an effort on active software processes – actually what now has resulted in Jaczone WayPointer. When I finally had time to take a good look at aspects it was in September 2002. I downloaded a lot of papers and studied them for a couple of days. After that I contacted Harold Ossher at IBM Research and Karl Lieberherr at North Eastern University in Boston. They are two of the leaders in this space. The most well-known guy on aspects is Gregor Kizcales. I tried to get his attention as well, but he was too busy at the moment.

In November 2002, I visited the IBM folks and spent a day with them understanding their work. After the meeting I was very impressed and excited about what they had done. I left their office, rushed to Newark airport; I had to run to the gate. This is normal. I was on my way to Stockholm. When I was seated in the plane, I ordered some champagne and began to relax and think a little. Suddenly, it struck me. Didn’t I do something similar before? Didn’t I write a paper on the same subject at OOPSLA’86 – the very first OOPSLA conference?

When I came to Stockholm, I started to hunt for the paper. It was a paper that discussed a topic that I mentioned as future work in my Ph. D. thesis from 1985. However, I got no interest for the ideas in the paper, so I decided to leave the subject. I felt it was too early to push those ideas. So I just forgot about it. My work on component-based development with objects and use cases was so successful so there was no room for new inventions. However, now I wanted to find the paper, I went to the publisher’s web site. I found the paper. I had to pay $95 to download it! My own paper!!!

The title of the paper is “Language Support for Changeable Large Real Time Systems”. In that paper I introduced several concepts – existion which represents a base, extension which represents separate functionality which you want to add to the existion. Instead of modifying the existion to invoke an extension, we used a mechanism to allow the extension to add behaviour into the existion. Thus from the perspective of the existion, no modification was needed. This means that you can add extensions after extensions without breaking the existion. The key idea is this: by keeping extensions separate from the base from the developer’s perspective, the system is much easier to understand, maintain and extend.

The basic idea sounded very much like what aspect orientation research is trying to achieve. But I needed confirmation. Two hours after I downloaded the paper I sent it to Karl Lieberherr. He responded: “Wow Ivar, this is an early paper on aspect-orientation”. He asked me if I had anything more. Since, I throw away everything I don’t work with; my first thought was that there was nothing more. However, I was excited, and my thoughts went back to the time before the paper. My memory asked me, “Didn’t you file a patent for a similar work?”

The patent was filed in 1981 and I made it as an employee of Ericsson. I called the Ericsson patent department and asked if they had saved the application. After a week they came back. I got a copy of the application – in Swedish. The application used typical patent language, so I had actually never understood it. It was written by a patent engineer. However, attached to the application was an internal Ericsson paper that described the whole idea in a couple of pages. It was a quite detailed paper with a practical example. This paper was also in Swedish. I had both documents translated by a professional translator into English, and you can find them on (look for published papers and aspect-oriented software development).

The patent was about what we called a sequence variator. It works at the micro-program instruction level. The highlight of the design is this: A program has a list of instructions. To each instruction, I added a flag. If this flag is turned on, it means that there is an extension that needs to be executed at this point. The sequence variator will fetch instructions from the extension, and thereafter resume at the next instruction. This branching is taken care of by the sequence variator. The developer of the original instructions do not need to code branch statements.

Alright, to make a long story short, Karl Lieberherr and Harold Ossher liked my early work. Karl wrote an email where he compared my early work with modern aspect-orientation: Extension ˜ Aspect, extension point ˜ join point, etc. I then wrote a couple of papers on aspects and use cases (see , and I was a result invited to give keynote talks at international conferences on aspect orientation. I was very happy being recognized for my early work. Now I am working on a book on aspects and use cases together with my colleague Pan-Wei Ng from Singapore. You will soon see this book in bookstores. I will be very happy if you buy it :-). I will be even happier if you read it (because this is not the same) :-). You can also ask me for a presentation. After all, I am in the business of promoting best practices in software development.

SOA by Ivar Jacobson

March 30, 2004

Before being invited to Tallahassee, I had never heard about it. I flew in to the city in the morning and back in the evening. I spent a day with the State of Florida. Bill Lucas did a wonderful job in making me feel very welcome and everyone I met was very friendly and interested in my work. I enjoyed my day very much. One of the questions we discussed was web services. The last couple of years services have become important elements for describing and building software. As with everything new, the software world has a tendency to believe that something fundamentally different has surfaced and that a new way of thinking is required. As a consequence we have got a whole arsenal of new concepts around the concept of services. We have got “service-oriented architectures”, “on demand”, “utility computing” name it. However, there is nothing fundamentally new with services. To organize software in services is an old practice.

Services were once a very important construct in RUP, actually in the version of RUP that we called 3.8. (It was the version prior to Rational buying my company, so it was called Objectory 3.8.) Unfortunately, the RUP team thought that downplaying services in RUP would make it significantly simpler. I disagreed with this opinion, but accepted it because almost everything else was adopted. It was very hard to argue for service-oriented design when the concept hadn’t hit the software industry. With Service-Oriented Architecture (SOA) on the table, the need is there.

In 1998, I wrote about services in the Unified Software Development Process book: Apart from providing use cases to its users, every system also provides a set of services to its customers. I made a distinction between end-users of the system and the customer who purchases a system for its users. For instance, a bank system has users which may be clients of the bank, and the bank itself is a customer of the system (maybe buying it from some system integrator). A customer acquires a suitable mix of services. Through these services the system will provide the necessary use cases for the users to do their business:

  • A use case specifies a sequence of actions: a thread is initiated by an actor, followed by interactions between the actor and the system, and completed and stopped after having returned a value to the actor. Usually, use cases don’t exist in isolation. For instance, the Withdraw Money use case assumes that another use case has created a user account and that the user’s address and other user data are accessible.
  • A service represents a coherent set of functionally related actions - a package of functionality - that is employed in several use cases. A customer of a system usually buys a mix of services to give its users the necessary use cases. A service is indivisible in the sense that the system needs to provide it completely or not at all.
  • Use cases are for users, and services are for customers. Use cases cross services, that is, a use case requires actions from several services. A service usually provides several use cases or parts of several use cases.

In the Unified Process, the service concept is in analysis (platform independent modelling) supported by service packages. The following can be noted about service packages:

  • A service package contains a set of functionally related classes.
  • A service package is indivisible. Each customer gets either all classes in the service package or none at all. Thus a service package is a configuration unit.
  • When a use case is realized, one or more service packages may be participants in the realization. Moreover, it is common for a specific service package to participate in several different use-case realizations.
  • A service package often has very limited dependencies toward other service packages.
  • A service package is usually of relevance to only one or a few actors.
  • The functionality defined by a service package can when designed and implemented be managed as a separate delivery unit. A service package can thus represent some “add-in” functionality of the system. When a service package is excluded, so is every use case whose realization requires the service package.
  • Service packages may be mutually exclusive, or they may represent different aspects or variants of the same service. For example, “spell checking for British English” and “spell checking for American English” may be two different service packages provided by a system. You configure the system with one or the other, but maybe not with both.
  • The service packages constitute an essential input to subsequent design and implementation activities, in that they will help structure the design and implementation models in terms of service subsystems. In particular, the service subsystems have a major impact on the system’s decomposition into binary and executable components. This is of course only true if the development is going top-down with no reuse of existing components: legacy systems, packaged solutions, web services. And fact is, we develop more and more with reusable components.

By structuring the system according to the services it provides, we prepare for changes in individual services, since such changes are likely to be localized to the corresponding service package. This yields a robust system that is resilient to change.  

Given that most software of today is developed with ready made components, why would you like to design an analysis model (a platform independent model) with service packages. There is one good reason: we still need to understand what we are doing. Building software is about understanding, understanding components developed by different vendors, divisions, teams. An analysis model - maybe even just a partial model - used as a start help you overcome these difficulties.  

Jolt Awards by Ivar Jacobson

March 17, 2004

Today I gave a keynote at the Software Development West conference in Santa Clara. Today is also a very special day that I have been looking forward to for a long time. The reason is that the Jolt award judges announced their result today at the conference. WayPointer is one of the products that made it all the way to the finals. Given that WayPointer is so different compared to other tools, I was not sure that the judges would have time to penetrate it enough to see its many values.

I gave my keynote on Aspects and Use Cases working together. The audience seemed to like it and I enjoyed talking about it. After all, it is work that I started more than 25 years ago - that thanks to the work of Gregor Kizcales, Harold Ossher and other friends - now finally can be harvested. As you can understand, I was quite passionate.

Directly after my keynote the Jolt awards were announced. There were a number of different categories and WayPointer competed in the category for Analysis and Design tools. I had to wait for quite some time before the decision was announced. To my great joy and pride, WayPointer won a Jolt Productivity Award.

The Jaczone team has really done an incredible job. They have implemented a tool using concepts and technologies that not yet are widely supported by commercial platforms. They have done it in a very effective way and perhaps most importantly in a way that is accessible but yet non-intrusive to users.

I am very proud of them. Hope you all understand why this tool is so important.  

Software Reuse by Ivar Jacobson

February 8, 2004

Many organizations are trying to achieve software reuse. Many of them think that they will achieve reuse if they just put their components in some sort of repository. Then they just expect others to reuse their valuable assets. I never cease to be surprised that people still do that. We have said for at least a decade that you don’t get any substantial reuse by just posting components. It seems as if people, instead of learning from others experience, always have to make the same mistakes as others over and over again.

The book I wrote with Martin Griss and Patrik Jonsson on Software Reuse is very explicit about how to achieve reuse. The subtitle of the book is: Architecture, Process and Organization for business success.

It all starts with Architecture. You design an architecture which identifies which components are reusable and which are not, thus a layered architecture. Usually two layers on top of middleware are enough. The top layer contains application components, which are not designed to be reusable. The second layer contains the domain components intended for reuse by several applications in the top layer. The only practical way to get a domain component is by designing an architecture in which the component has a clear role. Without this architectural setting, a component will never really be reused.

Process comes next. The way you develop the domain components is different from how you develop application components. They are documented for reuse. We suggested in our book that you design a façade for each domain component. This façade contains an extract of the models of the component, an extract defining how the component can be reused. In case the domain is big enough (e.g. banking, telecom, airline), the façades can through careful design evolve into a more powerful tool – a domain-specific language (DSL). Instead of designing on top of the interfaces of the domain components, expressed through their façades, you will design using a domain specific language.

Domain components also come with a kit containing tools for its reuse, examples of how to reuse it, and other things that help in getting it reused.

Developing application components is different. Application components don’t require to be documented for reuse. Instead they are designed using domain components and through interaction with other application components.

Finally Organization. In order to get successful reuse, you also need to develop an organization which maps 1:1 to the architecture. This means that for each component in the architecture there is a corresponding responsibility in the organization. Higher level components are the responsibility of a subsystem-owner. Lower level components are the responsibility of an individual developer. Without such a simple mapping between architecture and organization it will be practically impossible to get good reuse. Such an organization will become an expert organization – people will become experts in a subject matter. It grows people that want to create quality products. I call such an organization an architecture-based organization as opposed to a project-based organization. A project-based organization has a line manager for each project. The manager should only care about his own project. Such an organization is counterproductive to reuse.

In an architecture-based organization, the project managers are not line managers. Instead they own the budget for their project. Using this budget they can buy resources from the line organization (that is the subsystem-owners with domain expert developers) to get their projects done in time. The line organization can work with several projects concurrently and they have to prioritize them based on delivery dates. Yes, there may be conflicts, but these are usually not large. The total costs are substantially lower because the domain components are developed and maintained by experts. Thus in the case of conflicts, more resources can be added to remove the conflict, and still the costs are much lower than with a project-based organization.  

The approach I just presented also has the advantage that you grow the reusable components as you work with real projects. You will start with an empty architecture, but you fill it as you go. You don’t sit there and speculate about what might be reusable; instead you design the components in the architecture that are first needed. They have probably not stabilized for the first project, so they may have to grow through several projects before they really become reusable without redesign.

To achieve reuse is not easy. People have tried simple solutions like class libraries and component libraries into which component designers post their components hoping that other people will reuse them. We have seen very little reuse coming this way. Managers have thought it was the lack of incentives so they have stimulated all kinds of initiatives to get reuse. This is ignorant. You will get reuse, but only by standing on top of an integration of A, P and O, that is Architecture, Process and Organization. In another postcard I will tell you how you can move to an architecture-based organization from a project-based organization without revolution. It is really fascinating to see how easy it can be done, given that you are smart. However, that is not a problem, since you are smart, aren’t you?  

Architecture by Ivar Jacobson

February 1, 2004

Singapore is one of my favourite cities in the world. I like it for its people, for its various kinds of delicious food and for its advanced software companies. Singapore is also the cleanest city in the world.

I have just finished a week of intense work, meeting customers in rather small but competent groups. Basically all customers have expressed that the week was very important and they are now looking into how to move forward. Thus I feel happy with my work. I will soon take a flight to Seoul in South Korea, but before doing so I will reflect on one of my concerns with RUP.

In my earlier email I said that I often get the following question? “Is there nothing in RUP you don’t like?” I responded:

“Of course, there are many things I don’t like. However, they are in comparison with what I like rather small.” I said that one of them is “The way RUP describes architecture is unnecessarily complex and confusing.” In this postcard I will elaborate on this concern.

The single most important determinant of the quality of a software system is its architecture. A good architecture is an understandable architecture, it allows a system to grow gracefully for years to come, and it forms a system that is built out of reusable assets or that has harvested such assets.

Develop architecture first
Developing the architecture should therefore be done as early as possible. Even in theory it is very difficult to change a poor architecture into a good one with incremental techniques such as refactoring. In practice it is close to impossible. The costs are too high for any business-oriented manager to accept and he/she will typically opt for quick fixes instead. A good architecture needs to be created when the cost of creating it is small or even non-existent. Prioritization of architectural work has a very good return on investment. It will reduce the need for redesign and minimize throw-away work during the remainder of the project.

Architecture is captured by a skinny executable system
However, architecture is not just a paper product. The architecture must be verified and validated. We do that by first building what I call the “skinny system”, a system that includes a backbone with enough muscles to be able to exercise it. It is a system in its own right. It has everything a system has, but only things that are significant. Thus, it has all significant paths through the use cases (or scenarios); it has all significant subsystems, components, classes, nodes. Usually this skinny system only includes 5-15% of the final code, but enough to demonstrate that the significant elements work. And most important, we know that this skinny system can grow to become the complete system. This is so because we have scrutinized all features and use cases and selected to implement (part of) those that carry the largest risk, have the highest priority, or are unique in some other way. The remaining parts of the system can then be added incrementally without disruption. This skinny system is accompanied by a paper product called the architecture description. But now, this paper product is verified and validated. The architecture is actually working.

The architecture descriptions are views of the models.
The models are the models that we have in RUP. Thus it is the use case model, the analysis model, the design model, the implementation model and the deployment model. Well nowadays we have more models. We have a user experience model, we have a domain model and when we work with asset based systems (software reuse) we have even more models.

So far there is no major difference in what RUP describes as an architecture description and how I think it should be presented. The problem comes now when we start to look at these views of models. In RUP each view has been given a name. They are the use case view, the logical view, the process view, the implementation view, and they don’t map exactly to the models. It means that the developers have to deal both with names of views and with names of models. It is just confusing. I have yet to meet one developer or one tech rep at Rational that understands both this view structure and the model structure. Even some top experts at Rational could never really explain how these structures were related to one another. Most people either understood the view structure or the model structure.

And it could have been made so simple.
Since the final product is described by its set of models, and architecture is about an extract of these models, there is no reason for having separate names for views. Instead just call them simply the architectural view of the use case model, the architectural view of the analysis model, the architectural view of the design model, etc. Most people I talked to agreed that this was a simplification, but I could not convince the key people…and I didn’t get a reason for their hesitation. The only reason, I was told, for keeping view names separate from model names was that for architecture we needed a process view and there was no process model. That is an argument that I don’t accept. If we need an architectural view, we most certainly need a model as well, since the models are the complete description of the system.

Thus the most natural way to deal with architecture is to describe it as an extract of the model structure and call this extract for the architectural views of the models.

This is the right approach for other reasons as well:

  • There are more models than the original 4+1. The more we get the harder it becomes to give names for views that are different from the names of the models.
  • With asset based development we get many more models; it becomes almost ridiculous to name its architectural views different than the models.
  • The user experience model is as important as other models from an architectural viewpoint, something the advocators of separate names originally didn’t agree with. Would we give the architectural view of that model a separate name? No!
  • Finally, test is nowadays not a separate model, but instead each of the other models has a view for testing (verification and validation). Thus we have test views of basically every model…are we going to give these separate names as well? No!  

Thus, this is my proposal for you RUP developers. It is my hope that you take the chance to simplify the presentation of one of the most important artefacts in the software industry. Make the architecture description what it ought to be – an extract of the complete set of system models and remove it from being a creature living side by side with the system. The most important reason is to make RUP easier to understand. RUP is complex enough without making it unnecessarily complex.  

Putting the "R" in RUP by Ivar Jacobson

January 15, 2004 

Let me first wish you a very happy new year 2004. I hope it will be an exciting year both personally and professionally. A lot of things are happening in my life right now, so my expectations are very high. My work on aspect-oriented software development is going very well and Jaczone is in a very thrilling growth period. My passion has never been higher.

Yesterday, I gave five talks here in Jacksonville, of which the talk to the Rational User Group in Florida had most attendees. I spoke about Use Cases and Aspects and about "What you didn't know about RUP". It is always demanding, but also fun, to speak to people who have followed my work for many years.

My talk about RUP is of course very positive to RUP. As most of you know, RUP was originally created in Sweden but at that time it was called Objectory. When Rational acquired my company in 1995, we changed the name to Rational Objectory Process and later in 1998, when UML was adopted; we again changed the name to Rational Unified Process. We wanted to surf on our success with UML.

To tell you the truth, I have never been happy with putting Rational in front of the Unified Process. It is OK to have the company branding in front of product names, but to put it in front of intellectual work is different. Personally, I don't like to have to use a company name every time I utter my approach of thinking. However, working for Rational made it not so hard for me, but all my friends out there working with customers don't want to use our brand every time they mention our approach. I can't see that the standard approach of software development should be branded by one single company, even if this company is large.

Since I express myself so positively about RUP, I often get the following question? Is there nothing in RUP you don't like?

Of course, there are many things I don't like. However, they are in comparison with what I like rather small. They are still in absolute terms very important. In this postcard I will just list them. In later postcards, I will explain what I mean.

These are the three top issues in RUP that I don't like:

The way RUP recommends us to do analysis is a compromise that won't help customers succeed.

  • The way RUP describes architecture is unnecessarily complex and confusing. I agree with what architecture is, but not with its presentation. Very few people understand what the architectural views are and how it is related to the different models being advocated.
  • RUP has grown and become to complex. Too complex for users of course, but even more complex for the poor people that will have to maintain and develop it further.

Of course, I have recipes for how to solve these problems … and many more. The user complexity will be eliminated with the help of tools such as WayPointer from IJI.

Complexity by Ivar Jacobson

November 15, 2003

Even if I am Swedish, it is not often that I give speeches in Sweden. However, once a year I have been invited to speak at the Nordic Rational User Conference. Thus, today I gave my talk about Use Cases and Aspects. This is probably my best talk ever. It is better received than anything I have talked about before. I think there are several reasons for this reaction. Use cases are already very well adopted. Aspects are new and hip. Use cases and aspects are really a couple - aspects are the missing link to keep use cases separate all the way down to code -- even down to runtime. If you want to learn more about use cases and aspects there are a couple of articles I have written on this subject, look at:

The conference ended with a panel discussion on the biggest challenges that we face in software. Each panellist was supposed to suggest one challenge only. The moderator then asked the audience to vote for the challenge they felt was most important. The superior winning challenge was Complexity in software development.

This was of course something I could wholeheartedly agree with. Since someone else gave the winning challenge I had to suggest something else: complexity in usage. Users usually only learn 10-20 percent of the features in an application. The rest they never learn. It is too complex, people don't read manuals, and even if they did, they would forget what they have read before putting it to use. 99% of all software of today is passive software. It is waiting for the user to figure out how to make the software useful. We need a new kind of software. We need active software. This is software that instead can figure out what the user is trying to accomplish and actively help him or her to be successful in doing just that.

The next question to the panellists was "How are we going to tackle complexity in software development". Here we heard all kinds of answers. I suggested that we need a new approach to software development. Software development has never been as complex as today. We need a new class of process & tools. We can't continue with a passive process like RUP and we can't continue using passive tools. We need active process & tools.

The winning proposal was that we need to invest more in training. About 70% of the audience voted for this proposal. Maybe 10% voted for active process & tools. I must admit I was quite disappointed. As if we have not invested in training over the years. Traditional training is simply not effective. It is done out of context with artificial examples and at a single point in time. With active processs and tools you learn as you work when you have a concrete business problem to solve. OK, I had to accept the answer, but to my inner self, I said that this will change. This is not the first time that I have suggested a new idea and almost no one liked it. A couple of years from now, I think we will see much more of active software. At the least I will work to make it happen.

UML by Ivar Jacobson

October 30, 2003

The largest conference on object technology is OOPSLA. The first OOPSLA conference was in 1986 and I have attended all of them but one. And, I have presented papers, or given tutorials or been on panels each time. Last year I decided not to go there. I wanted to break the rule (to go to OOPSLA) so that I wouldn't become a slave under it. This year the conference took place in Los Angeles, or more precisely in Anaheim - the home of Disneyland.

OOPSLA is a meeting-place for pioneers in software technology from all over the world. Everywhere there are friends from many years back, and we really get together and discuss what we are doing, what we want to do, what we think is hot and what we need to change.

This year I participated in two panels, one on Reuse and Repositories, another on Model Driven Architecture. The most interesting and passionate one was the one on MDA. Much thanks to my friend Dave Thomas (also on the advisory board of Jaczone) who dared to question the UML as well as MDA, as envisioned by OMG, in a very direct way.

Dave: "UML is currently a language with no conventional syntax, and not even a comprehensive standard way for tool interchange (XMI is both awkward and inconsistently implemented). UML was designed by committee, most of whom are methodologists and hence have little experience with language design. UML lacks a simple semantic account as an executable language. There is no published semantic account although proponents claim it is well defined via action semantics."

In general (not only from Dave) I understand the critique against UML as follows. UML is designed by people who have no experience from traditional language design, which means that the language is a mess. Even worse, they have no experience of real software development but they come from the methodology camp with no real software product background. These people have never developed any real software.

Of course, in a setting like OOPSLA Dave's words fell in very good soil. It was a very popular standpoint.

While I am not completely positive to everything in UML, I heard nothing really new in Dave's position. To me it was a dejà vue. I have heard the same critique for more than thirty years. I heard it when I introduced component-based development with visual modelling back in 1967. I heard it when we developed SDL that became a world standard in 1976 within telecommunications. And now I hear it again.

I was originally very critical to how we worked with UML 1.0. Some people wanted a very intuitive approach and define the language with basically just a notation, some meta-model diagrams and plain English text. UML 1.0 became hopeless to understand. I advocated that we should apply classical language design techniques. Starting with an abstract syntax, build a static semantic model on top of the syntax, introduce dynamic semantic domains. I didn't suggest that we should define the operational semantics formally. I made this compromise primarily because most people wouldn't understand it and very few people would care. Moreover this wouldn't be different in approach from most other language designs. I have personally done a lot of language design work when we defined SDL and CHILL, I also did it when working with my doctoral thesis. Thus from a practical point of view I couldn't recommend it. Also, I felt comfortable we could add it later.

During the work with UML 1.1 my approach was adopted. We didn't formalize the dynamic semantic domains. We defined the operational semantics textually only.

Thus it is not correct to say that language-design amateurs defined UML. My own thesis was a definition of a modelling language using classical language design techniques.

It is also not true that UML was designed by people with no practical experience from software development. I was not the only one with many years of hard work in real software development. The UML team was also backed by 10,000's of developers working behind the scenes and applying the technologies being proposed. We had reference groups all around the world that helped us understand the needs to satisfy.

This was UML 1.1.

With UML 2.0 the situation changed. A lot of new people entered the scene, and a committee took over. With "a fresh look", they changed everything they didn't like. And they added what their "fresh look" told them should be added. Personally, I was so bored working in a committee so I stayed out of the work almost completely (I had done language designs three times before, so I couldn't feel any excitement). I said "almost" because I had to get involved on one occasion. That was when the committee decided to remove use cases from UML. Well, they removed the kind of use cases we have had, and replaced them with something different…and then they called this new thing use cases. They were so arrogant, that they told me, without a blink, that I had never understood use cases, but now they had got them right. They voted in the committee and agreed to remove our use cases. Luckily, people outside the committee set things straight and put use cases back into UML.

Many members of that committee had never produced any useful software. Some members were really competent, but the politics became a burden. Now the committee took a lot of time, they were delayed by years, and the resulting proposal UML 2.0 is very complex. Still, I am optimistic. The interest for UML is so high and there are so many people that are willing to fix what potentially is broken. Thus, I am convinced without a single doubt that UML will continue to be successful. It represents very much what a good part of the software community wants to have.

However, this part is not in majority. It may today be 20% of the software community. The remaining 80% have not adopted visual modelling at all. Twenty years ago I believe that it was less than 5% that used visual modelling.

Thus I believe the reason UML is criticized have other roots than bad language designs. The critique represents symptoms not the root cause. I believe that the roots of the critique are that some people don't believe in visual modelling as such but that textual languages work better.

The critique is healthy. UML will most certainly become better defined. We will get better and better tools. The tools will make software development less complex, we will be more productive, get higher quality, and get software much faster --- very much thanks to UML and how you can apply UML.

Anyway, it was a very good panel. People love a good fight. Dave was the clear winner, but that was a given. He was playing on home ground.

During the aftermath of the heated discussion, someone said that whether you are for or against UML or MDA rests on religious grounds. That is something I can wholeheartedly agree with. On the other hand, this is what I heard when I introduced components, use cases, … I have been very honest about it. I have never been able to prove that my approach is better than anyone else's. At best, I have been able to make it believable.

With UML and MDA we have a similar situation. It is very much about gut feeling. Either your gut feeling tells you that UML and MDA are good, or it does not. Your way of working will be coloured by your feelings.

Regarding UML, I have absolutely not a single doubt about its long-term success. About MDA, I am very sympathetic. I know that MDD (model-driven development) has been successful and will become even more successful in the future. Whether MDA will be successful is a question of execution, i.e., how well OMG and its members succeed in implementing the vision. I will support them, and I wish them very good luck.  

Seoul by Ivar Jacobson

October 27, 2003 

This is the third time that I have been in Seoul this year. I must like Seoul and Koreans very much because going from San Francisco to Seoul is a twelve-hour flight! It is actually longer between San Francisco and Seoul than from Stockholm to Seoul. Most Europeans would not have guessed that.

One objective for this trip was to meet Samsung Electronics - a company that have impressed me very much. They are world-leaders in so many areas and technologies. Their people are world-class and they work very hard. I think they shape the future.  

IBM Rational in Korea had arranged for me to talk at the Korea University. Rational and the university celebrated an agreement on using Rational Rose. It is so refreshing to talk to students. They are so immediate and spontaneous. Lots of laughs, autographs and photos.

There is one thing I would like to ask you. What do you think is the most important property one needs to be successful in software development? The answer is being SMART. I think we should teach students what it means to be smart, so we always recognize non-smart behaviour.

Being smart means that you do what you need to do, no more and no less. For instance, when applying RUP, do it right, do it as agile as possible. I have never believed in just buying RUP and have your people apply it. They will do too much or they will just give up. When I meet customers and get project reviews, I often see that people are not allowing themselves to be smart. Often they work too hard and do too much, or they do too little and have given up. You need to apply as little process as possible, but NOT less. The trick is to know what is less. For that you need experience.

Smart is not the same as intelligent. I know many people who are very intelligent but not smart. Smart requires that you have knowledge, not just experience. Smart is not just about how to apply techniques, it is also about how to deal with customers, managers, and the unexpected.

As an example, I see agile as a property you get from a process like RUP by being smart. Personally I think RUP applied in a smart way is the most agile we can be.

I would like to see more on this subject. If anyone has seen a book or a paper that develops the meaning of smart, I would love to read it.  

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