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Archive for the ‘Business Rules’ Category

Domain Model Pattern

Saturday, April 21st, 2007

When implementing a domain model, often object-relational mapping technologies are used. Like many tools, with their use comes the danger of abuse – abuse to the point of invalidating the benefits of the pattern itself.

From some pointers about how to use (and not to use) these tools, see why object-relational mapping sucks.

Martin Fowler’s has this to say about the Domain Model Pattern:

At its worst business logic can be very complex. Rules and logic describe many different cases and slants of behavior, and it’s this complexity that objects were designed to work with. A Domain Model creates a web of interconnected objects, where each object represents some meaningful individual, whether as large as a corporation or as small as a single line on an order form.

In short, using Object-Oriented techniques to handle the complexity.

A more comprehensive discussion about what happens when it is not used can be found under the Anemic Domain Model Anti-Pattern:

The basic symptom of an Anemic Domain Model is that at first blush it looks like the real thing. There are objects, many named after the nouns in the domain space, and these objects are connected with the rich relationships and structure that true domain models have. The catch comes when you look at the behavior, and you realize that there is very little behavior on these objects. Indeed often these models come with design rules that say that you are not to put any domain logic in the the domain objects. Instead there are a set of service objects which capture all the domain logic. These services live on top of the domain model and use the domain model for data.

The fundamental horror of this anti-pattern is that it’s so contrary to the basic idea of object-oriented design; which is to combine data and process together. The anemic domain model is really just a procedural style design…

In terms of Domain-Driven Design, this pattern is also known as Domain Layer.

Domain Models do a lot for encapsulating Business Rules, thus making them amenable to automated testing. This hinges on keeping the Domain Model independent of things related to Data Access.

It is therefore almost required to use some kind of Object/Relational Mapping tool to make it possible to persist objects belonging to the domain model to databases and other kinds of storage.

The use of DataSets in .NET is often a sign of the Anemic Domain Model Anti-Pattern.

One thing to keep in mind when working on a domain model is that you probably won’t get it “right” the first time, and will have re-work the division of responsibility a couple of times. Techniques like Test-Driven Development help out immensely for that.

Dataset – O/R mapping rumble at TechEd MVP Dinner

Thursday, November 9th, 2006

So, last night I was at the MVP dinner in TechEd and everything was nice. We had a nice meal, conversation was nice, weather was… nice. And then the volume started to rise, slowly at first, so as you don’t quite notice it. After a bit, you kind of stop talking and look around. And then I hear it…

<WWF announcer voice>
Are you ready… to RUMBLE !?!?
</WWF announcer voice>

It was Datasets vs. O/R mapping, a slight twist on the infamous datasets vs. custom objects debate, all over again. They pulled me in, kicking and screaming, I swear, I really do. The lines were drawn, maintainability, performance, all the things that architects like to philosophize about in terms of other people’s work.

Anyway, I won’t give you the play-by-play ‘cause we were there almost all night. I’ll just cut to the chase.

First things first – any comparison of solutions without the context of a problem leads nowhere, fast, and stays there. So the first question I asked (when I got the chance to speak) was “are we talking about querying/reporting here?” and the answer was something like “well, yeah, but a lot of other things too”. So my suggestion was that we discuss the solutions in terms of two contexts – querying/reporting and OLTP.

What I mean by OLTP is the data-updating kind of work that you do on certain items. Examples of this include “insert order”, “change customer address”, and “discount product”. Querying/reporting doesn’t change data, and often involves dealing with large sets of data pulled from different kinds of entities (in ERD terms).

Luckily, my suggestion to deal with them separately was accepted. Secondly, I proposed that an object model (specifically implementing the Domain Model pattern) designed for OLTP would perform poorly when used for querying/reporting – simply because it wasn’t designed for it. The structure of a domain model is such that it makes it possible to define / implement business rules in one place. That’s possible, not easy.

Well, the dataset people weren’t going to just hand me the OLTP side of the equation without a fight, so they mentioned how easy it was to just “AcceptChanges”, and that my way was much more complex. My rebuttal came in the form of a question (are you seeing a pattern here?): Do you just swallow DbConcurrencyExceptions are do you throw all the user’s changes away when it happens? I didn’t quite make out the answer since there was a lot of mumbling going on, but I’m pretty sure they had one. I mean, you can’t develop multi-user systems using datasets without running into this situation.

The example that clinched OLTP was this. Two users perform a change to the same entity at the same time – one updates the customer’s marital status, the other changes their address. At the business level, there is no concurrency problem here. Both changes should go through. When using datasets, and those changes are bundled up with a bunch of other changes, and the whole snapshot is sent together from each user, you get a DbConcurrencyException. Like I said, I’m sure there’s a solution to it, I just haven’t heard it yet.

Now, here’s where things get interesting. I didn’t say that using a domain model automatically solves this problem. Rather, I described how each client could send a specific message, one a ChangeMaritalStatusMessage, the other a ChangeAddressMessage, to the server – in essence, giving the server the context in which each bit of data is relevant. The server could just open a transaction, get the customer object based on its Id, call a method on the customer (ChangeMaritalStatus or ChangeAddress), and commit the transaction. If two of these messages got to the server at the same time, the transactions would just cause them to be performed serially, and both transactions would succeed. The important part here is not losing the context of the changes.

When we talked about querying/reporting, things seemed quite a bit clearer. Datasets, or rather datatables seemed like a fine solution – most 3rd party controls support them out of the box. One guy mentioned that datasets performed poorly for large sets of data and that by designing custom entities for the result set, he could improve performance and memory utilization by, like, 70%. To tell you the truth, I think that if you need the performance, do it, if not, just use datasets. There isn’t much of an issue of correctness.

Just as an ending comment, in response to something someone said about scalability, I asked if they were reporting against the live OLTP data. The response was “yes”. Well, there’s a database scalability problem if I ever saw one. OLTP works most correctly when employing transactions that have an isolation level of serializable. The problem with them is that they lock up the whole table, or get blocked when a table scan is going on. Querying often results in a table scan. You can see the problem. Anyway, a common solution to this problem is to just reduce the isolation level, a quick fix that improves performance almost immediately. You take one hit in that your reports may be showing incorrect data, especially if they do aggregate type work. You might take another hit if your OLTP transactions need to do aggregate type work themselves. That second hit is pretty much unacceptable. A different solution is to accept the fact that the heaviest querying can usually show data that isn’t up to date up to the second.

In such a solution, you would have another database for reporting. It wouldn’t be just a replica of the OLTP database, but rather a lot more denormalized – which is a really not nice way of saying designed for reporting. You could then move the data from your OLTP database to the reporting database in some way (more to come on this topic) and you increase the scalability of your database. Just to define that a bit better – your OLTP database will be able to handle more transactions per unit of time, and reports will run faster, meaning that you will both improve their latency and the number of queries that can be handled per unit of time.

Anyway, I was pretty tired after all that, but if I had to sum it up I’d say something like this: before debating solutions, define the problem, you get a lot more insight into the solutions and you get it faster. That’s just win-win all around.

DDD – why bother?

Saturday, October 7th, 2006

Domain Driven Design (DDD), alongside its growing popularity, is experiencing some growing pains. The Domain Model pattern, documented in the Patterns of Enterprise Application Architecture book, is at the heart of DDD yet the division of responsibility between it and other DDD patterns like Service Layer isn’t quite clear. To make matters worse, the value of the Domain Model pattern relative to simpler code-generation techniques remains vague. The one thing that has reached a wide consensus is that it requires a higher level of skill to employ these techniques than continue using the widespread procedural programming practices. There is one overwhelming reason to do it anyway, though, and that is that it is the cheapest way to get a system up and running right. The reasoning behind this has to do with business rules.

An exceedingly large number of systems are being built and modified today in order to support business rules. Beyond just computerizing the management of data in the enterprise, today’s systems are required to computerize the business processes that use that data, and these processes are built upon business rules.

A rule is composed of two main elements, a clause and an action. The clause defines under what circumstances the action is to be activated. An example of a rule employed in the business environment might be “if the customer is a preferred customer, then give them a 5% discount on all orders”. The rich behavior of an enterprise is governed by these interacting rules. Consider the result of adding another business rule like “if the customer has ordered $100,000 or more in the last year, then they are to be considered a preferred customer”. If a customer is not preferred, but then sends in a new order that puts them over the limit, how is the system to behave? Conversely, what if a preferred customer cancels an order bringing them under the limit?

I’ve seen too many projects that have been tasked with implementing these kinds of behaviors yet were unable to get the system running right. Customers that should have gotten discounts didn’t in some cases, and those that should not have enjoyed a discount did at times. After much time was spent trying to track down what part of the code was wrong, changing some code, testing, over and over again, an executive decision was made to put the system into production as is. The harm to the business was deemed cheaper in this case then not putting the system in production. Is it any wonder that business is skeptical of IT’s ability to handle the agile enterprise of the future where, not only will the business rules be more complex, they will be changing all the time.

The Domain Model pattern encapsulates these business rules in such a way that they will be run even when not directly invoked. This is especially critical when one rule triggers another. Intelligent use of OO principles when designing the domain can help you altogether avoid the jump in complexity found in Business Rules Engines.

Finally, we need to understand that supporting techniques like Object/Relational (O/R) mapping are but a means, and not the end. The discussions around DDD often get mired down in the relative costs of O/R mapping and procedural code generation. Persistence is a solved problem, a technical problem that has no meaning to business. Is it not time to raise the discussion to the level of business? If the only problem you are trying to solve is the manipulation of data in a database, then don’t bother with DDD and its descendents. It won’t make your life any easier. If, on the other hand, business has gotten sick of IT deciding for them how to run their business; if you are the one tasked with building the right system, you just won’t be able to do it unless you build the system right – DDD won’t be a bother, but a necessity.

SOA Meets Business Rules

Tuesday, September 5th, 2006

After 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 🙂

To map, or not to map?

Saturday, March 11th, 2006

I had this discussion with Clemens when he was last here in Israel – his position, as was so eloquently stated here, was against, while I was pro. The question he raised “To map, or not to map?” he himself answered, “to map”. The question remaining was how to map; write the sql yourself, or let some tool write/generate it for you.

The overarching question is: what do you REALLY gain by O/R mapping?

(As an aside, among the comments of his post are those using the acronym ORM. Please stop – that acronym is already taken by Object Role Modeling.)

I’ve been using O/R mapping techniques on mission critical projects for some time now, and if I wanted to compare it to what I did before, it would not be to writing all the sql by hand. I don’t remember ever doing that – there was always code generation involved. Because, let’s face it – there’s a lot of drudgery involved for things that aren’t performance critical. No reason to do THAT by hand.

So, for me, the ONE THING that O/R mapping gives me better than what I did before is this:

O/R mapping gets me better object-oriented business logic.

That’s it.

Like Clemens said, if you “don’t know SQL and RDBMS technology in any reasonable depth”, don’t expect to get good performance. Obviously this is true for any technique. But I guess that empirically speaking, the percentage of people without said knowledge is larger in the group where you don’t HAVE to write sql.

So, I’ll bet you’re asking yourself, “if that’s all Udi gets from O/R mapping, why does he keep doing it?” Or maybe you’re asking yourself “should I get a beer? This is getting long…”

The fact of the matter is that I don’t know a better way to write business logic than by using OO techniques. I grant that data is important, but the reason that many applications are built is business logic – there’s something that this new system can/should do, that the old systems couldn’t (often using the same data).

If I could sum up my understanding of Clemens position, it would be this:

A lot of developers probably aren’t experienced, or knowledgeable enough the use O/R mapping well. Therefore writing the sql yourself is better.

While I agree with the first statement, and I think that the same could be said about communication, threading, .net and many other things, I don’t think that the conclusion logically follows.

So, I guess I would sum up my position like this:

If you would like to develop a persistent domain model, O/R mapping techniques will probably help you. If you would like your solution to perform well, you should probably learn how databases work, as well as what the O/R mapping tool does under the covers.

SOA, mediation, and the holy code

Tuesday, September 27th, 2005

Ronan Bradley of www.WebServices.org predicts the failure of SOA solutions based on “coded frameworks”. To say I disagree would be an understatement. There is one section in particular that disturbs me:

“My aversion to code is not based an abstract principle. Rather, each line of code the organization develops is custom for that organization and (unfortunately) sometimes for that project. As a consequence it must be maintained and evolved over time. Furthermore, the knowledge about what that code does must be maintained in the organization and evolved over time. This is a potentially huge cost and distraction for IT organizations, which need to focus on solving business problems rather than maintaining integration code.”

1. Custom code is not necessarily integration code.
2. Some business problems are about getting access to legacy data stuck in some proprietary format.
3. IT maintains and develops code. That’s why it exists.

I worry that people will start thinking of SOA as “buy product from vendor, drag and drop, done”. Developers will always be writing code.

Let’s go back to the pipe-dreams of business-rule systems. You know, those hyper-flexible monstrosities that end-users (of all people) would define the rules.

Why don’t we, as an industry, JUST GET OVER IT.

There will always be code, as in custom code. Code without a solid design is a maintainence nightmare. Design without architecture is the right solution to the wrong problem. Architecture without requirements is answering the right question asked by the wrong person.

Nothing has changed.

Developing software will continue to be hard.

And no matter how many three letter acronyms you throw at it, software development will continue to be hard. If you don’t look at the whole lifecycle, you’re bound to optimize the small, and ruin the large.

Are we done with the hype yet?

Can we all just get back to work?

Architecture, Business Rules, and Aspects, oh my !

Friday, November 14th, 2003

I’ve been reading a lot from the agile management blog lately, and I came upon this entry about implementing business rules with aspects. If you haven’t yet read this previous entry about the division of the system architecture not only along system lines, but also along “risk of change” lines, then I suggest you read it first.

First of all, I would like both developers and managers to read the previous entry because of its profound meaning. We CAN and should separate different parts of the system having differing levels of risk. Once again, “3-tier architectures” don’t address these issues. So, if we are dividing the architecture along risk lines as well, then obviously the UI would be the riskiest – having the highest probability to change – over the life of the project.

However, business rules are often considered quite stable. Why ? Because their time-line of change is often stretched out over many project life-times – rather obvious really, business rules deal with the business, not the project. During development of the project we are often given the requirements in such a way that it is difficult to know what is domain knowledge and what is a business rule. It takes effort to separate out what are the business rules – what has changed in the past, and what will change in the future.

For example, in an academic project I performed some time ago, I was given a set of requirements including: 1. A student can register to a given course once in a semester. 2. A student can register to a project in a semester. Which is the business rule, which is the domain ? In this case (1) is the domain, and (2) is the rule – “a project” meaning “only one project” as I later found out. This rule changed sometime after my second alpha to “A student can register to only one project alone in a semester, but several projects in the same semester as long as they have a partner for each of those projects.”

As it is apparent, I, as a developer, have to take into account these risk/change factors and change my architecture accordingly. Ever since that project I have always created a business rules layer separate from the infamous “BL” ( Business Logic ).

Now, getting to the issue of implemeting using aspects. I am a big proponent of AOP, however I often find alternative implementations to be more desirable. Most of the examples given for the use of AOP including logging, transactions, security and others that can be made part of a framework, as .Net has done in many cases. Many have pushed Java’s superiority because of AspectJ, and although .Net doesn’t have an Aspect.Net yet ( although various developments are under way ), I have yet to miss it. Clemens Vasters has done some truly incredible stuff in the use of attributes in .Net for implementing AOP stuff. I’ve always thought that attributes should be used that way. I find that there is one basic flaw in the conclusion to using aspects for connecting business rules to systems. The entire white paper is here. ( Yes, its a pdf unfortunately – only good for print really, Jakob Nielsen thinks so too. ) The basic premise is that I’m building an entire system in an OO manner, which I’ve stopped doing some time ago for these reasons. Clemens has great insights on this as well, see them here.

When using an SOA, your UI, or any other system needing services for that matter, will be sending messages to the guts of your system – the “BL” for you hardcore 3-tier-guys. Let’s call the thing receiving messages in this case the Gateway. All the gateway does is receive messages ( like “Register student number 12 to course number 15 in semester 21” ) and pass them on to the appropriate handler. The word “handler” hear is used like in the term “event handler” for a reason: The receipt of a message is an event. In the white-paper the authors refer to these events as a problem that has to be dealt with. Why ? Because when working in an object oriented fashion, you would have to intercept the call to: new Student(12).RegisterToProject(93); in order to handle the event, ie check/activate a business rule. Aspects are great for this sort of thing. However, when working in a service-oriented fashion, you would send a message of type “RegisterStudentToProject” with the parameters StudentID and ProjectID as above. No need to intercept any call since it has to first go through the gateway. The gateway would then pass the message to the business rules engine which would then find and activate the appropriate rules before and after the actual call to register the student.

The rules engine does something like this:

If ( ActivateBusinessRulesForMessageAndReturnTrueIfCanMakeCall(myMessage) )

The business rules themeselves are implemented in a separate layer than the engine. The mapping between rules and messages is also done in a layer separate from both the engine and the rules. Once we have a layer for each of these, we have architecturally separated the parts that change more often in the system from the rest of it. One can also move to a more dynamic model. One in which you define a language for defining rules, and the mapping to messages as well. Thus, changes could be made by changing a configuration file instead of recompiling any part of the system.

Note that when you have lots of rules and the order for activating them matters, you should move to a commercial rule engine instead of implementing your own. You’ll see that performance becomes an issue as the number of rules increases.

I hope that I’ve managed to introduce yet another strength of the SOA over the pure OO paradigm. Tell me what you think ! Where does the SOA fall short ? Where does the OOA beat the SOA ? Am I full of it ?


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“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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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
Chapter: Introduction to SOA    Article: The Enterprise Service Bus and Your SOA

97 Things Every Software Architect Should Know

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