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Started blogging on the IASA sitePosted in General
The International Association of Software Architects (IASA) has a blog of its own and I’ve started posting there as well. If you’re subscribed to this blog, you probably won’t see anything new from me there, but there are other bloggers there well worth reading so go and take a look.
SOA costs, savings, & valuePosted in SOA
After reading Harry Pierson’s comments on an SOA workshop he attended presented by Thomas Erl, and the rest of the reuse bubble growing and popping, I wanted to add some comments from my experience in using SOA in the wild. First of all, the “reuse” is bull. In the cases where I found high reuse, I also found a function instead of a service. After some redesign, the function, and all the other “services” that “reused” it all collapsed into one, larger service. No more reuse. No need, really. Second, about the costs of an SOA approach. They are higher. I repeat, it is more expensive to do SOA than continue what you are doing today. Developers are, by and large, not used to asynchronous programming. Doing SOA properly involves a mind-shift from the architects, through the team leaders, and all the way to the programmers. Call it a learning curve if you want. This costs. I don’t know if its 30%, or more, or less. You will not be saving money by moving to SOA, at least, not tomorrow morning. I assert that all this doesn’t really matter. The reason company’s should move to SOA has to do with value. The looser coupling found in, and between, systems will decrease the time it takes to change and augment them. This translates to “business agility” (how I hate these hype-laden words). By decreasing overall complexity, the lifespan of systems will increase. In other words, you will be rewriting systems less, thus getting a higher return on investment on the systems that you’ve already built. Another “value-add” of the decreased complexity is that IT will be able to build larger and more powerful systems than before – integrating more processes and sharing more data across the enterprise. This, in turn, brings more of the right information to the right people at the right time, allowing them to make better decisions. You won’t see all these things appearing in the cost-analysis of an SOA project I’m afraid. Bottom line, do SOA for the value, or don’t do it at all.
High performance SOA – an oxymoron? Umm, no.Posted in Architecture
From the SOA in Action Blog, following up on a recent ZapThink Flash:
First of all, SOA does not necessarily imply XML. Second of all, even if you use XML in server environment (I do, every day), while performance may be worse than binary serialization, I have yet to see it be the system bottleneck. Sending out unnecessarily large sets of data, or sending the same data over and over again (as occurs in an RPC world) has been problematic in many of the systems that I’ve seen. While one could blame XML for making the bloat worse, one might also blame the architect for the bloat in the first place.
From my experience, the price of the abstraction is negligible. Disregard for the impact of network latency comes with one helluva penalty, much higher than the service abstraction. Poorly designed services often suffer in this regard, so one could mistaken the performance hit as being caused by the abstraction. That is, if one was an analyst and not somebody actually doing the work. One thing I will grant, though: “At large sites with a lot of users and traffic, … performance is a huge challenge.” Regardless of SOA.
Web Service Software Factory – Data Access CRUD!And I don’t mean CRUD as in Create,Read,Update,Delete. I haven’t been following the factories much but David Hayden’s recent post pulled me back in. Here’s an example of the kind of solution that the factory creates: I thought that object orientation was already accepted as good practice, but here comes Microsoft splitting up data and behavior once again. Business components that have only behavior, and business entities that contain only data (relationships between entities doesn’t count as behavior) <shudder/>. If anything, the business components, when you actually look at the code in them, are more service layer objects than anything else. Which kind of makes you wonder why there is a separate Service Implementation layer. Is it because the service implementation is technology dependent? The answer is yes. Wouldn’t it be great if we could have service layer objects that were technology independent? Then we could take the code in the “business components” and put it there, and do away with an entire layer. You know where this is heading. The tried and true Domain Model pattern and its friends. Its just that this whole “data access” paradigm that Microsoft keeps pushing gets on my nerves. It just does not hold up in complex domains – I know, I’ve tried. I’ve also consulted on many other projects that have tried, and seen them get to the point of no return. The point where programmers just don’t know what the domain logic is – because its spread all over the place: service implementation, business components, entities, data access, stored procedures… Its at that point when they have to “ship” so that the project won’t be called a failure. Then they scrap the whole thing, and start working on version 2.0 which will be totally different! They use a rules engine! I’ve already wrote about the kinds of successes I’ve seen there. OK, enough whining. Do your own design. There are other patterns besides what Microsoft puts out. Read them, use them. Just because there’s a factory that autogenerates thousands of lines of code, doesn’t mean that they’re the right thousands of lines of code.
On application responsivenessPosted in Development
Dr. Dobb’s recently published an article on “Application Responsiveness” by Joe Duffy where he gives a very thorough treatment of threading issues in UIs. I felt that the discussion of the solutions was a bit light, but there was one solution missing that, in my opinion, is more important than all the rest. The kinds of systems that I work on almost always have the client side being asynchronously updated by events published by a server. If there’s one thing I’ve learned, its that threading is a HARD problem. What makes it hard is that it adds another dimension to the complexity of the system. Which is why I’ll do almost anything to have the code that I’m looking at behave single-threaded. The solution involved first separating out classes that will be touched by only one thread. This means that all view classes (in MVC terms) will be accessed only on the control thread. Secondly, classes that receive information asynchronously from the server will only run on the background thread. Classes in the model (in MVC terms) will not be thread-aware, therefore it is the responsibility of other classes to interact with the model in a thread-safe manner. All other classes, like the controllers (in MVC terms) will be run on both/multiple threads. Despite the need to marshal a call from the background thread to the foreground one (which has been done to death), these controllers have state that needs to be protected. Enter the ContextBoundObject. This framework class enables you to quite simply put a [Synchronization] attribute on a class that inherits from it, and voila, its thread safe. Not only that, but it will share a single lock with all the other objects that inherit from ContextBoundObject, as long as they’re in the same Synchronization Domain. Don’t worry, it’s easy. Just have a single object that is also a ContextBoundObject be the one that causes all others to be created. If you’re using a container like spring, then the first object would be that which asks spring to initialize. OK, so technologically – you’re all set. But doing the design according to the constraints mentioned above isn’t trivial. Especially when it comes to the Model objects. But believe me, it’s much easier than an endless hunt after deadlocks and race conditions.
Put me and him in the same room and you get…Posted in The Team
If I’m Statler, the one on the right, can you guess who’s Waldorf?
MSMQ scale out questionIt appears that the questions are getting more concrete around my Autonomous Services article. This one comes from Eric who asks: “Udi, Your article caught my attention because we are currently trying to figure out the “infrastructure implementation” piece of the puzzle in an MSMQ cluster scenario. I didn’t understand the term “remote transactional reads”; can you describe it as it relates to this architecture? The problem we’ve encountered is how do we make it easy for our ops team to just add/remove servers from the cluster, and have the load redistribute itself properly. MSMQ tied to virtual IPs by itself doesn’t seem smart enough. We’re toying with both HW load balancing, and/or some NLB/MOM/AppCenter interactions (with programming layers to make it work.)” Eric, the current version of MSMQ lacks the remote transactional receive capability – meaning that if your “application” is trying to perform a “Receive” operation on a queue that is located on a remote machine in a transactional context, it will not work. The next version of MSMQ is supposed to “fix” this. Why would you want such a feature? Well, if you put a single queue on a clustered server (for availability) and had many other servers using that queue as their input queue, you’d have the ability to add servers at runtime to handle increases in load. However, since the handling of a message from a queue often requires a transaction, the current version of MSMQ won’t support this out of the box. What you could do is have some sort of dispatcher application that would send messages to the other servers. When a server would be ready to receive a message (not under heavy load), it could send the dispatcher a message saying just that. The dispatcher would store the return address (ResponseQueue) so that when a message would arrive, it could send that message to the server. This scenario would have each server have its own input queue and be aware of the dispatcher. The dispatcher would not have to know about the other servers directly – it would just store the return addresses of the messages it receives. The result of this behavior would cause the messages to be sent transactionally to only one server, which would, in turn, transactionally receive the message from its local queue and process it. I hope that answers your question Eric. If you’d like more information, feel free to follow up.
Re: Autonomous ServicesPosted in Architecture
Following my article in the Architecture Journal, I’ve been getting quite a stream of emails asking for more information. The latest one came from Alex and I’d like to relate his thoughts here, with my comments inserted inline. “Udi, I read with big interest your article in the architecture journal. I liked 1. You are saying “When services interaction is asynchronous we avoid I’d like to address your first question first. “But if the data on service B “2. I think the pattern you were discussing should emphasize the reliability Reliability is a big topic. I’ve posted on the topic before and you can find the summary here. There really are two parts to the reliability of notifications. Consider a smart client that is subscribed to a service which sends it stock updates once a second. When the user turns off his computer, should all those stock updates sent from then until he turns his computer on again be lost or not? What if it wasn’t a smart client, but a different service? What if wasn’t stock updates, but the results of certain actions requested earlier? It really does depend on the scenario. However, the point that you bring up about handling errors when communication is fully asynchronous is a good one, and a topic for a separate post. “3. It may be obvious but I think it is worth mentioning that a service Again, I’m not sure such a broad statement would hold. Certain data is published in aggregates where, even if certain branches are unaffected, the entire aggregate is sent. This especially holds true for reference data that legacy systems may not have stored locally. Desigining a quality service contract is difficult, and goes hand in hand with properly assigning responsibility to various services. Well, Alex, I hope that covers your questions. If something still is a bit unclear, feel free to fire me an email to Blog@UdiDahan.com.
SOA Meets Business RulesAfter reading this article you just might be thinking that business rules management systems (BRMS’s) are the key to what SOA was supposed to bring (now that we’re in the trough of disillusionment) – that is, if you haven’t tried working with these beasts before. There are several now-well-known fallacies around BRMS’s. One is that business analysts write the business rules, in plain English, and these rules do not require a programmer to enter/code them into the system; the BRMS handles all that. “Costly, time-consuming transformation from business terms to programmer requirements and subsequent implementation can be reduced or eliminated. This in turn empowers business analysts to create and maintain the business logic directly, allowing them to make changes with little or no IT intervention.” But, the author forgets to mention who performs these trivial activities: “After testing and validation the business logic can be deployed to a business rules server.” This brings me to the single most important thing anyone should know about the business rules approach. Employing a rules engine opens up the possibility that the system will behave non-deterministically. Consider that only 3 non-linear equations are needed to create chaotic behavior, and try to imagine what will happen in a system with hundreds and thousands of business rules that affect each other. Yes, business rules often end up changing data which, in turn, causes other business rules to be activated. No, it is not humanly possible to look at such a set of rules and predict what will happen when a certain event occurs. You can fire such an event in a test environment and see what will happen. When the results aren’t what you wanted (that would be all the time), you can use the BRMS’s to show you which rules were run as a result of that event. Let’s see a business analyst debug that. “Plain English” my butt. Let’s not go too much further on the BRMS on its own, but rather view it in the light of service-oriented architectures. In the article, an approach is shown that is supposed to bring you the best of both SOA and the Business Rules Philosophy. I’m afraid that my experience has been otherwise. The author states: “The business rules server may be implemented as a Web Service that is accessible to many SOA enabled applications across the organization. By supporting shared business logic within the SOA architecture that can be addressed by many disparate applications, organizations can reduce redundancy, speed implementation, lessen inconsistency and improve the overall efficiency of both the applications and the business processes they serve.” This desire to concentrate all business logic into a single BRMS embodies the 11th fallacy of enterprise computing, as put forth by James Gosling “Business logic can and should be centralized”. Not to mention that this goes against the grain of SOA where each service is autonomous and is entirely responsible for all of its data and behavior. There’s another reason why the business rules community is pro centralization – the BRMS’s are so damned expensive. Anyway, I don’t want to be all doom and gloom today so I’ll end on a positive note. While good OO practices and the use of the Domain Model Pattern will take you VERY far in making business rules explicit, and, therefore, their maintenance and evolution much less costly, sometimes you really neeed a BRMS. Just so you know, the investment you made in the domain model is not written off when you “upsize” to business rules – the rules themselves are written using the concepts exposed in the domain. As for the service, well, its message handlers keep on working the same as they always did; parsing messages and making calls on the domain model. The business rules will just respond to the events raised by the domain; message handlers don’t need to call into the BRMS. Oh, and the next time somebody tells you how business analysts will be doing the work instead of programmers, ask them if they’re willing to take the debugging too 🙂
[Podcast] Autonomous Services and Pub/SubIn this podcast, we address questions about autonomous services, publish/subscribe communication, exceptions, data duplication, reuse, and governance. Resources: 1. Autonomous Services and Enterprise Entity Aggregation Download directly here. Want more? Go to the “Ask Udi” archives.
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Recommendations
Bryan Wheeler, Director Platform Development at msnbc.com
“Udi Dahan is the real deal. We brought him on site to give our development staff the 5-day “Advanced Distributed System Design” training. The course profoundly changed our understanding and approach to SOA and distributed systems. Consider some of the evidence: 1. Months later, developers still make allusions to concepts learned in the course nearly every day 2. One of our developers went home and made her husband (a developer at another company) sign up for the course at a subsequent date/venue 3. Based on what we learned, we’ve made constant improvements to our architecture that have helped us to adapt to our ever changing business domain at scale and speed If you have the opportunity to receive the training, you will make a substantial paradigm shift. If I were to do the whole thing over again, I’d start the week by playing the clip from the Matrix where Morpheus offers Neo the choice between the red and blue pills. Once you make the intellectual leap, you’ll never look at distributed systems the same way. Beyond the training, we were able to spend some time with Udi discussing issues unique to our business domain. Because Udi is a rare combination of a big picture thinker and a low level doer, he can quickly hone in on various issues and quickly make good (if not startling) recommendations to help solve tough technical issues.” November 11, 2010 
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“Udi, one of the great minds in this area. A man I respect immensely.” 
Ian Robinson, Principal Consultant at ThoughtWorks
"Your blog and articles have been enormously useful in shaping, testing and refining my own approach to delivering on SOA initiatives over the last few years. Over and against a certain 3-layer-application-architecture-blown-out-to- distributed-proportions school of SOA, your writing, steers a far more valuable course." 
Shy Cohen, Senior Program Manager at Microsoft
“Udi is a world renowned software architect and speaker. I met Udi at a conference that we were both speaking at, and immediately recognized his keen insight and razor-sharp intellect. Our shared passion for SOA and the advancement of its practice launched a discussion that lasted into the small hours of the night. It was evident through that discussion that Udi is one of the most knowledgeable people in the SOA space. It was also clear why – Udi does not settle for mediocrity, and seeks to fully understand (or define) the logic and principles behind things. Humble yet uncompromising, Udi is a pleasure to interact with.” 
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“I have known Udi for many years having attended his workshops and having several personal interactions including working with him when we were building our Composite Application Guidance in patterns & practices. What impresses me about Udi is his deep insight into how to address business problems through sound architecture. Backed by many years of building mission critical real world distributed systems it is no wonder that Udi is the best at what he does. When customers have deep issues with their system design, I point them Udi's way.” 
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“I have been following Udi’s blog and podcasts since 2007. I’m convinced that he is one of the most knowledgeable and experienced people in the field of SOA, EDA and large scale systems. Udi helped Frequentis to design a major subsystem of a large mission critical system with a nationwide deployment based on NServiceBus. It was impressive to see how he took the initial architecture and turned it upside down leading to a very flexible and scalable yet simple system without knowing the details of the business domain. I highly recommend consulting with Udi when it comes to large scale mission critical systems in any domain.” 
Simon Segal, Independent Consultant
“Udi is one of the outstanding software development minds in the world today, his vast insights into Service Oriented Architectures and Smart Clients in particular are indeed a rare commodity. Udi is also an exceptional teacher and can help lead teams to fall into the pit of success. I would recommend Udi to anyone considering some Architecural guidance and support in their next project.” 
Ohad Israeli, Chief Architect at Hewlett-Packard, Indigo Division
“When you need a man to do the job Udi is your man! No matter if you are facing near deadline deadlock or at the early stages of your development, if you have a problem Udi is the one who will probably be able to solve it, with his large experience at the industry and his widely horizons of thinking , he is always full of just in place great architectural ideas. I am honored to have Udi as a colleague and a friend (plus having his cell phone on my speed dial).” 
Ward Bell, VP Product Development at IdeaBlade
“Everyone will tell you how smart and knowledgable Udi is ... and they are oh-so-right. Let me add that Udi is a smart LISTENER. He's always calibrating what he has to offer with your needs and your experience ... looking for the fit. He has strongly held views ... and the ability to temper them with the nuances of the situation. I trust Udi to tell me what I need to hear, even if I don't want to hear it, ... in a way that I can hear it. That's a rare skill to go along with his command and intelligence.” Eli Brin, Program Manager at RISCO Group “We hired Udi as a SOA specialist for a large scale project. The development is outsourced to India. SOA is a buzzword used almost for anything today. We wanted to understand what SOA really is, and what is the meaning and practice to develop a SOA based system. We identified Udi as the one that can put some sense and order in our minds. We started with a private customized SOA training for the entire team in Israel. After that I had several focused sessions regarding our architecture and design. I will summarize it simply (as he is the software simplist): We are very happy to have Udi in our project. It has a great benefit. We feel good and assured with the knowledge and practice he brings. He doesn’t talk over our heads. We assimilated nServicebus as the ESB of the project. I highly recommend you to bring Udi into your project.” 
Catherine Hole, Senior Project Manager at the Norwegian Health Network
“My colleagues and I have spent five interesting days with Udi - diving into the many aspects of SOA. Udi has shown impressive abilities of understanding organizational challenges, and has brought the business perspective into our way of looking at services. He has an excellent understanding of the many layers from business at the top to the technical infrstructure at the bottom. He is a great listener, and manages to simplify challenges in a way that is understandable both for developers and CEOs, and all the specialists in between.” 
Yoel Arnon, MSMQ Expert
“Udi has a unique, in depth understanding of service oriented architecture and how it should be used in the real world, combined with excellent presentation skills. I think Udi should be a premier choice for a consultant or architect of distributed systems.” Vadim Mesonzhnik, Development Project Lead at Polycom “When we were faced with a task of creating a high performance server for a video-tele conferencing domain we decided to opt for a stateless cluster with SQL server approach. In order to confirm our decision we invited Udi. After carefully listening for 2 hours he said: "With your kind of high availability and performance requirements you don’t want to go with stateless architecture." One simple sentence saved us from implementing a wrong product and finding that out after years of development. No matter whether our former decisions were confirmed or altered, it gave us great confidence to move forward relying on the experience, industry best-practices and time-proven techniques that Udi shared with us. It was a distinct pleasure and a unique opportunity to learn from someone who is among the best at what he does.” 
Jack Van Hoof, Enterprise Integration Architect at Dutch Railways
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Neil Robbins, Applications Architect at Brit Insurance
“Having followed Udi's blog and other writings for a number of years I attended Udi's two day course on 'Loosely Coupled Messaging with NServiceBus' at SkillsMatter, London. I would strongly recommend this course to anyone with an interest in how to develop IT systems which provide immediate and future fitness for purpose. An influential and innovative thought leader and practitioner in his field, Udi demonstrates and shares a phenomenally in depth knowledge that proves his position as one of the premier experts in his field globally. The course has enhanced my knowledge and skills in ways that I am able to immediately apply to provide benefits to my employer. Additionally though I will be able to build upon what I learned in my 2 days with Udi and have no doubt that it will only enhance my future career. I cannot recommend Udi, and his courses, highly enough.” 
Nick Malik, Enterprise Architect at Microsoft Corporation
“You are an excellent speaker and trainer, Udi, and I've had the fortunate experience of having attended one of your presentations. I believe that you are a knowledgable and intelligent man.” 
Sean Farmar, Chief Technical Architect at Candidate Manager Ltd
“Udi has provided us with guidance in system architecture and supports our implementation of NServiceBus in our core business application. He accompanied us in all stages of our development cycle and helped us put vision into real life distributed scalable software. He brought fresh thinking, great in depth of understanding software, and ongoing support that proved as valuable and cost effective. Udi has the unique ability to analyze the business problem and come up with a simple and elegant solution for the code and the business alike. With Udi's attention to details, and knowledge we avoided pit falls that would cost us dearly.” 
Børge Hansen, Architect Advisor at Microsoft
“Udi delivered a 5 hour long workshop on SOA for aspiring architects in Norway. While keeping everyone awake and excited Udi gave us some great insights and really delivered on making complex software challenges simple. Truly the software simplist.” Motty Cohen, SW Manager at KorenTec Technologies “I know Udi very well from our mutual work at KorenTec. During the analysis and design of a complex, distributed C4I system - where the basic concepts of NServiceBus start to emerge - I gained a lot of "Udi's hours" so I can surely say that he is a professional, skilled architect with fresh ideas and unique perspective for solving complex architecture challenges. His ideas, concepts and parts of the artifacts are the basis of several state-of-the-art C4I systems that I was involved in their architecture design.” 
Aaron Jensen, VP of Engineering at Eleutian Technology
“Awesome. Just awesome. We’d been meaning to delve into messaging at Eleutian after multiple discussions with and blog posts from Greg Young and Udi Dahan in the past. We weren’t entirely sure where to start, how to start, what tools to use, how to use them, etc. Being able to sit in a room with Udi for an entire week while he described exactly how, why and what he does to tackle a massive enterprise system was invaluable to say the least. We now have a much better direction and, more importantly, have the confidence we need to start introducing these powerful concepts into production at Eleutian.” 
Gad Rosenthal, Department Manager at Retalix
“A thinking person. Brought fresh and valuable ideas that helped us in architecting our product. When recommending a solution he supports it with evidence and detail so you can successfully act based on it. Udi's support "comes on all levels" - As the solution architect through to the detailed class design. Trustworthy!” 
Chris Bilson, Developer at Russell Investment Group
“I had the pleasure of attending a workshop Udi led at the Seattle ALT.NET conference in February 2009. I have been reading Udi's articles and listening to his podcasts for a long time and have always looked to him as a source of advice on software architecture. When I actually met him and talked to him I was even more impressed. Not only is Udi an extremely likable person, he's got that rare gift of being able to explain complex concepts and ideas in a way that is easy to understand. All the attendees of the workshop greatly appreciate the time he spent with us and the amazing insights into service oriented architecture he shared with us.” 
Alexey Shestialtynov, Senior .Net Developer at Candidate Manager
“I met Udi at Candidate Manager where he was brought in part-time as a consultant to help the company make its flagship product more scalable. For me, even after 30 years in software development, working with Udi was a great learning experience. I simply love his fresh ideas and architecture insights. As we all know it is not enough to be armed with best tools and technologies to be successful in software - there is still human factor involved. When, as it happens, the project got in trouble, management asked Udi to step into a leadership role and bring it back on track. This he did in the span of a month. I can only wish that things had been done this way from the very beginning. I look forward to working with Udi again in the future.” 
Christopher Bennage, President at Blue Spire Consulting, Inc.
“My company was hired to be the primary development team for a large scale and highly distributed application. Since these are not necessarily everyday requirements, we wanted to bring in some additional expertise. We chose Udi because of his blogging, podcasting, and speaking. We asked him to to review our architectural strategy as well as the overall viability of project. I was very impressed, as Udi demonstrated a broad understanding of the sorts of problems we would face. His advice was honest and unbiased and very pragmatic. Whenever I questioned him on particular points, he was able to backup his opinion with real life examples. I was also impressed with his clarity and precision. He was very careful to untangle the meaning of words that might be overloaded or otherwise confusing. While Udi's hourly rate may not be the cheapest, the ROI is undoubtedly a deal. I would highly recommend consulting with Udi.” Robert Lewkovich, Product / Development Manager at Eggs Overnight “Udi's advice and consulting were a huge time saver for the project I'm responsible for. The $ spent were well worth it and provided me with a more complete understanding of nServiceBus and most importantly in helping make the correct architectural decisions earlier thereby reducing later, and more expensive, rework.” 
Ray Houston, Director of Development at TOPAZ Technologies
“Udi's SOA class made me smart - it was awesome. The class was very well put together. The materials were clear and concise and Udi did a fantastic job presenting it. It was a good mixture of lecture, coding, and question and answer. I fully expected that I would be taking notes like crazy, but it was so well laid out that the only thing I wrote down the entire course was what I wanted for lunch. Udi provided us with all the lecture materials and everyone has access to all of the samples which are in the nServiceBus trunk. Now I know why Udi is the "Software Simplist." I was amazed to find that all the code and solutions were indeed very simple. The patterns that Udi presented keep things simple by isolating complexity so that it doesn't creep into your day to day code. The domain code looks the same if it's running in a single process or if it's running in 100 processes.” 
Ian Cooper, Team Lead at Beazley
“Udi is one of the leaders in the .Net development community, one of the truly smart guys who do not just get best architectural practice well enough to educate others but drives innovation. Udi consistently challenges my thinking in ways that make me better at what I do.” Liron Levy, Team Leader at Rafael “I've met Udi when I worked as a team leader in Rafael. One of the most senior managers there knew Udi because he was doing superb architecture job in another Rafael project and he recommended bringing him on board to help the project I was leading. Udi brought with him fresh solutions and invaluable deep architecture insights. He is an authority on SOA (service oriented architecture) and this was a tremendous help in our project. On the personal level - Udi is a great communicator and can persuade even the most difficult audiences (I was part of such an audience myself..) by bringing sound explanations that draw on his extensive knowledge in the software business. Working with Udi was a great learning experience for me, and I'll be happy to work with him again in the future.” 
Adam Dymitruk, Director of IT at Apara Systems
“I met Udi for the first time at DevTeach in Montreal back in early 2007. While Udi is usually involved in SOA subjects, his knowledge spans all of a software development company's concerns. I would not hesitate to recommend Udi for any company that needs excellent leadership, mentoring, problem solving, application of patterns, implementation of methodologies and straight out solution development. There are very few people in the world that are as dedicated to their craft as Udi is to his. At ALT.NET Seattle, Udi explained many core ideas about SOA. The team that I brought with me found his workshop and other talks the highlight of the event and provided the most value to us and our organization. I am thrilled to have the opportunity to recommend him.” 
Eytan Michaeli, CTO Korentec
“Udi was responsible for a major project in the company, and as a chief architect designed a complex multi server C4I system with many innovations and excellent performance.” 
Carl Kenne, .Net Consultant at Dotway AB
“Udi's session "DDD in Enterprise apps" was truly an eye opener. Udi has a great ability to explain complex enterprise designs in a very comprehensive and inspiring way. I've seen several sessions on both DDD and SOA in the past, but Udi puts it in a completly new perspective and makes us understand what it's all really about. If you ever have a chance to see any of Udi's sessions in the future, take it!” Avi Nehama, R&D Project Manager at Retalix “Not only that Udi is a briliant software architecture consultant, he also has remarkable abilities to present complex ideas in a simple and concise manner, and... always with a smile. Udi is indeed a top-league professional!” 
Ben Scheirman, Lead Developer at CenterPoint Energy
“Udi is one of those rare people who not only deeply understands SOA and domain driven design, but also eloquently conveys that in an easy to grasp way. He is patient, polite, and easy to talk to. I'm extremely glad I came to his workshop on SOA.” 
Scott C. Reynolds, Director of Software Engineering at CBLPath
“Udi is consistently advancing the state of thought in software architecture, service orientation, and domain modeling. His mastery of the technologies and techniques is second to none, but he pairs that with a singular ability to listen and communicate effectively with all parties, technical and non, to help people arrive at context-appropriate solutions. Every time I have worked with Udi, or attended a talk of his, or just had a conversation with him I have come away from it enriched with new understanding about the ideas discussed.” Evgeny-Hen Osipow, Head of R&D at PCLine “Udi has helped PCLine on projects by implementing architectural blueprints demonstrating the value of simple design and code.” 
Rhys Campbell, Owner at Artemis West
“For many years I have been following the works of Udi. His explanation of often complex design and architectural concepts are so cleanly broken down that even the most junior of architects can begin to understand these concepts. These concepts however tend to typify the "real world" problems we face daily so even the most experienced software expert will find himself in an "Aha!" moment when following Udi teachings. It was a pleasure to finally meet Udi in Seattle Alt.Net OpenSpaces 2008, where I was pleasantly surprised at how down-to-earth and approachable he was. His depth and breadth of software knowledge also became apparent when discussion with his peers quickly dove deep in to the problems we current face. If given the opportunity to work with or recommend Udi I would quickly take that chance. When I think .Net Architecture, I think Udi.” 
Sverre Hundeide, Senior Consultant at Objectware
“Udi had been hired to present the third LEAP master class in Oslo. He is an well known international expert on enterprise software architecture and design, and is the author of the open source messaging framework nServiceBus. The entire class was based on discussion and interaction with the audience, and the only Power Point slide used was the one showing the agenda. He started out with sketching a naive traditional n-tier application (big ball of mud), and based on suggestions from the audience we explored different solutions which might improve the solution. Whatever suggestions we threw at him, he always had a thoroughly considered answer describing pros and cons with the suggested solution. He obviously has a lot of experience with real world enterprise SOA applications.” 
Raphaël Wouters, Owner/Managing Partner at Medinternals
“I attended Udi's excellent course 'Advanced Distributed System Design with SOA and DDD' at Skillsmatter. Few people can truly claim such a high skill and expertise level, present it using a pragmatic, concrete no-nonsense approach and still stay reachable.” 
Nimrod Peleg, Lab Engineer at Technion IIT
“One of the best programmers and software engineer I've ever met, creative, knows how to design and implemet, very collaborative and finally - the applications he designed implemeted work for many years without any problems!” Jose Manuel Beas “When I attended Udi's SOA Workshop, then it suddenly changed my view of what Service Oriented Architectures were all about. Udi explained complex concepts very clearly and created a very productive discussion environment where all the attendees could learn a lot. I strongly recommend hiring Udi.” 
Daniel Jin, Senior Lead Developer at PJM Interconnection
“Udi is one of the top SOA guru in the .NET space. He is always eager to help others by sharing his knowledge and experiences. His blog articles often offer deep insights and is a invaluable resource. I highly recommend him.” 
Pasi Taive, Chief Architect at Tieto
“I attended both of Udi's "UI Composition Key to SOA Success" and "DDD in Enterprise Apps" sessions and they were exceptionally good. I will definitely participate in his sessions again. Udi is a great presenter and has the ability to explain complex issues in a manner that everyone understands.” Eran Sagi, Software Architect at HP “So far, I heard about Service Oriented architecture all over. Everyone mentions it – the big buzz word. But, when I actually asked someone for what does it really mean, no one managed to give me a complete satisfied answer. Finally in his excellent course “Advanced Distributed Systems”, I got the answers I was looking for. Udi went over the different motivations (principles) of Services Oriented, explained them well one by one, and showed how each one could be technically addressed using NService bus. In his course, Udi also explain the way of thinking when coming to design a Service Oriented system. What are the questions you need to ask yourself in order to shape your system, place the logic in the right places for best Service Oriented system. I would recommend this course for any architect or developer who deals with distributed system, but not only. In my work we do not have a real distributed system, but one PC which host both the UI application and the different services inside, all communicating via WCF. I found that many of the architecture principles and motivations of SOA apply for our system as well. Enough that you have SW partitioned into components and most of the principles becomes relevant to you as well. Bottom line – an excellent course recommended to any SW Architect, or any developer dealing with distributed system.” Consult with Udi
Guest Authored Books
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© Copyright 2005-2011, Udi Dahan. email@UdiDahan.com
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