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Archive for the ‘Usability’ Category



Queries, Patterns, and Search – food for thought

Sunday, April 28th, 2013

fishWith all the talk of CQRS, the area that doesn’t get enough treatment (in my opinion) is that of queries. Many are already beginning to understand the importance of task-based UIs and how that aligns to the underlying commands being sent, validated, and processed in the system as well as the benefits of messaging-centric infrastructure (like NServiceBus) for handling those commands reliably. When it comes to queries, though, it isn’t nearly as well understood what it means for a query to be “task based”.

Starting with CRUD

Let’s start with a traditional CRUD application and work our way out from there.

In these environments, we often see users asking us to build “excel-like” screens that allow them to view a set of data as well as sort, filter, and group that data along various axes. While we might not get this requirement right away, after some time users begin to ask us to allow them to “save” a certain “query” that they have set up, providing it some kind of name.

That, right there, is a task-based query and it is the beginning of deeper domain insight.

Pattern matching

Any time a user is repeatedly running the same query (this can be once a day or some other unit of time) there is some scenario that the business is trying to identify and is using that user as a pattern-matching engine to see if the data indicates that that scenario has occurred.

It’s quite common for us to get a requirement to add some field (often a boolean or enum) to an entity which defaults to some value and then see that same field used in filtering other queries. These measures are sometimes instituted as a temporary stop-gap while a larger feature is being implemented, though (as the saying goes) there is nothing more permanent than a temporary solution.

Where we developers go wrong

The thing is, many developers don’t notice these sorts of things happening because we don’t actually look at the kinds of queries users are running.

One excellent technique to better understand a domain is to sit down with your users while they’re working and ask them, “what made you run that query just now?”, “why that specific set of filters?”.

What I’ve noticed over the years is that our users find very creative ways to achieve their business objectives despite the limitations of the system that they’re working with. We developers ultimately see these as requirements, but they are better interpreted as workarounds.

I’ll talk some more about how a software development organization should deal with these workarounds in a future post, but I want to focus back in on the queries for now.

Oh, and don’t get me started on caching or NoSQL, not that I think that those tools don’t provide value – they do, but they’re only relevant once you know which business problem you’re solving and why.

Not all queries are created equal

Even before bringing up the questions I described in the previous section, any time you get query-centric requirements the first question to ask is “how often will the user be running this specific query?”.

If the answer is that the specific query will be run periodically (every day, week, etc), then drill deeper to see what pattern the user will be looking for in the data. If the person you’re talking to doesn’t know to answer that question, then go find someone who does. Every periodic query I’ve seen has some pattern behind it – and in my conversations with thousands of other developers over the years, I’ve seen that this is not just my personal experience.

But there is a case where a query does get run repeatedly without there being a pattern behind it.

I know this sounds like I’m contradicting myself, but the distinction is the word “specific” that I emphasized above.

There are certain users who behave very differently from other users – these users are often doing what I call research, i.e. the “I don’t know what I’m looking for but I’ll know it when I see it” people.

These researchers tend to repeatedly query the data in the system however they tend to run different queries all the time. This is the reason why traditional data warehouse type solutions don’t tend to work well for them. Data warehouses are optimized for running specific queries repeatedly.

Keeping the Single-Responsibility Principle in mind – we should not try to create a single query mechanism that will address these two very different and independently evolving needs.

And now on to Search

Search is a feature that is needed in many systems and whose complexity is greatly underestimated.

While the developer community has taken some decent strides in understanding that search needs to be treated differently from other queries, the common Lucene/Solr solutions that are applied are often overwhelmed by the size of the data set on which the business operates.

The problem is compounded by our user population being spoiled by Google – that simple little text box and voila, exactly what you’re looking for magically appears instantaneously. They don’t understand (or care) how much engineering effort went into making that “just work”.

Lucene and Solr work well when your data set isn’t too large, and then they become pretty useless as the quality of their results degrades. The thing is that many of us in IT tend to work on projects where we have an unrealistically small data set that we use to test the system and, at these volumes, it looks like our solutions work great. But if you have 20 million customers, do you think a full text search on “Smith” is going to find just the right one?

Larger data sets require a relevance engine – something that feeds off of what users do AFTER the query to influence the results of future queries. Did the user page to the next screen? That needs to be fed back in. Did they click on one of the results? That needs to be fed back in too. Did they go back to the search and do another similar search right after looking at a result – that should possibly undo the previous feedback.

And that’s just relevance for beginners.

You know what makes Google, you know, Google? It’s that they have this absolutely massive data set of what users do after the query that informs which results they return when. You probably don’t have that. That and search is/was their main business for many years – I’m betting that it’s not your main business.

You should discuss this with your stakeholders the next time they ask for search functionality in your system.

In closing

I know that the common CQRS talking points tell you to keep your queries simple, but that doesn’t mean that simple is easy.

It takes a fair bit of domain understanding to figure out what the queries in the system are supposed to be – what tasks users are trying to achieve through these queries. And even when you do reach this understanding, convincing various business stakeholders to change the design of the UI to reflect these insights is far from easy.

It often seems like the reasonable solution to give our users everything, to not limit them in any way, and then they’ll be able to do anything. What ends up happening is that our users end up drowning in a sea of data, unable to see the forest for the trees, ultimately resulting in the company not noticing important trends quickly enough (or at all) and therefore making poor business decisions.

Even if your company doesn’t believe itself to be in “Big Data” territory, I’d suggest talking with the people on the “front lines” just in case. Many of them will report feeling overwhelmed by the quantity of stuff (to use the correct scientific term) they need to deal with.

It’s not about Lucene, Solr, OData, SSRS, or any other technology.

It’s on you. Go get ’em.



Search and Messaging

Sunday, November 1st, 2009

search
One question that I get asked about quite a bit with relation to messaging is about search. Isn’t search inherently request/response? Doesn’t it have to return immediately? Wouldn’t messaging in this case hurt our performance?

While I tend to put search in the query camp in the when keeping the responsibility of commands and queries separate, and often recommend that those queries be done without messaging, there are certain types of search where messaging does make sense.

In this post, I’ll describe certain properties of the problem domain that make messaging a good candidate for a solution.

Searching is besides the point – Finding is what it’s all about

Remember that search is only a means to an end in the eyes of the user – they want to find something. One of the difficulties we users have is expressing what we want to find in ways that machines can understand.

In thinking about how we build systems to interact with users, we need to take this fuzziness into account. The more data that we have, the less homogeneous it is, the harder this problem becomes.

When talking about speed, while users are sensitive to the technical interactivity, the thing that matters most is the total time it takes for them to find what they want. If the result of each search screen pops up in 100ms, but the user hasn’t found what they’re looking for after clicking through 20 screens, the search function is ultimately broken.

Notice that the finding process isn’t perceived as “immediate” in the eyes of the user – the evaluation they do in their heads of the search results is as much a part of finding as the search itself.

Also, if the user needs to refine their search terms in order to find what they want, we’re now talking about a multi-request/multi-response process. There is nothing in the problem domain which indicates that finding is inherently request/response.

Relationships in the data

When bringing back data as the result of a search, what we’re saying is that there is a property which is the same across the result elements. But there may be more than one such property. For example, if we search for “blue” on Google Images, we get back pictures of the sky, birds, flowers, and more. Obvious so far – but let’s exploit the obvious a bit.

When the user sees that too many irrelevant results come back, they’ll want to refine their search. One way they can do that is to perform a new search and put in a more specific search phrase – like “blue sky”. Another way is for them to indicate this is by selecting an image and saying “not like this” or “more of these”. Then we can use the additional properties we know about those images to further refine the result group – either adding more images of one kind, or removing images of another.

Here’s something else that’s obvious:

Users often click or change their search before the entire result screen is shown.

It’s beginning to sound like users are already interacting with search in an asynchronous manner. What if we actually designed a system that played to that kind of interaction model?

Data-space partitioning

Once we accept the fact that the user is willing to have more results appear in increments, we can talk about having multiple servers processing the search in parallel. For large data spaces, it is unlikely for us to be able to store all the required meta data for search on one server anyway.

All we really need is a way to index these independent result-sets so that the user can access them. This can be done simply by allocating a GUID/UUID for the search request and storing the result-sets along with that ID.

Browser interaction

When the browser calls a server with the search request the first time, that server allocates an ID to that request, returns a URL containing that ID to the browser, and publishes an event containing the search term and the ID. Each of our processing nodes is subscribed to that event, performs the search on its part of the data-space, and writes its results (likely to a distributed cache) along with that ID.

The browser polls the above URL, which queries the cache (give me everything with this ID), and the browser sees which resources have been added since the last time it polled, and shows them to the user.

If the user clicks “more of these”, that initiates a new search request to the server, which follows the same pattern as before, just that the system is able to pull more relevant information. When implementing “not like this”, this performs a similar search but, instead of adding to the list of items shown, we’re removing items from the list shown based on the response from the server.

In this kind of user-system interaction model, having the user page through the result set doesn’t make very much sense as we’re not capturing the intent of the user, which is “you’re not showing me what I want”. By making it easy for the user to fine tune the result set, we get them closer to finding what they want. By performing work in parallel in a non-blocking manner on smaller sets of data, we greatly decrease the “time to first byte” as well as the time when the user can refine their search.

But Google doesn’t work like that

I know that this isn’t like the search UI we’ve all grown used to.

But then again, the search that you’re providing your users is more specific – not just pages on the web. If you’re a retailer allowing your users to search for a gift, this kind of “more like this, less like that” model is how users would interact with a real sales-person when shopping in a store. Why not model your system after the ways that people behave in the real world?

In closing

If we were to try to make use of messaging underneath “classical” search interaction models, it probably wouldn’t have been the greatest fit. If all we’re doing at a logical level is blocking RPC, then messaging would probably make the system slower. The real power that you get from messaging is being able to technically do things in parallel – that’s how it makes things faster. If you can find ways to see that parallelism in your problem domain, not only will messaging make sense technically – it will really be the only way to build that kind of system.

Learning how to disconnect from seeing the world through the RPC-tinted glasses of our technical past takes time. Focusing on the problem domain, seeing it from the user’s perspective without any technical constraints – that’s the key to finding elegant solutions. More often than not, you’ll see that the real world is non-blocking and parallel, and then you’ll be able to make the best use of messaging and other related patterns.

What are your thought? Post a comment and let me know.



Object/Relational Mapping and Scalability

Saturday, April 21st, 2007

“How come there is no talk about scaling these ORMs?”.

The answer is simple.

You don’t have to.

Or, if you think you do, you’re probably using them wrong.

An O/R mapper should NOT live in its own tier.

Object/Relational Mappers never stand alone. They are used to provide persistence for something else – either for the Domain Model Pattern or for the Active Record pattern.

In terms of scalability, again these patterns usually don’t stand by themselves, but rather are hosted by something else. When used on the client side, say in a smart client application, then scalability isn’t often considered. There are some kinds of smart clients where hitting the database on most user interactions will bring the system to its knees, but that’s again an issue of database scalability. The common solution is some kind of client-side caching.

Anyway, the two main parameters you need to look at for your common and high-load scenarios when using an O/R mapper are these:

  • How many times do you hit the DB per business action.
  • How many objects/records/rows/columns do you bring into memory per business action.

You should be looking at appropriate uses of Lazy Loading for both of them.

Finally, keep in mind that O/R mappers are only part of your solution. Measure and optimize wisely.



Thoughts about usability

Tuesday, January 16th, 2007

After reading “What about Usability”, Jeremy’s latest installment of his “Better Software Development” series (my words, not his) I got flooded with a bunch of thoughts. Mostly things that I’ve wanted to blog about before but didn’t. So please pardon the disjointed nature of the following notes.
 

Since I’m writing this while on the plane to the Software Architecture Workshop in Switzerland, I’m reminded of a discussion I had with Arjen Poutsma at this same workshop last year. I think that the original topic had to do with Web Services, but it meandered around quite a bit. I think it started by me saying that services should not expose CRUD style operations. Arjen countered by mentioning that most user interfaces in line-of-business applications exposed the same model to the user by having them fill out data in grids. My retort to that was that while humans can get used to almost anything as long as its consistent, that doesn’t mean that it is a good solution. In the systems that I work on there is usually an HCI (human-computer interaction) person on the project who designs the UI, mostly around the tasks they perform. These tasks often corresponded very well to the coarse-grained messages we employed in terms of SOA. We finally agreed that the successor of SOA would be TOA (Task-Oriented Architecture) in its aggregation of client-side aspects to the already server-centric principles of SOA.
 

A different topic that came up in a recent meeting in one of the projects I’m consulting was how long users expect to wait for a response from the system. What made the HCI person rethink his design was my suggestion that certain algorithms could be deployed client-side and since their performance for the kinds of work the user would do most of the time was on the order of a couple of hundered millis, we could run them “interactively” – as in, on every mouse-click. This input eventually brought about a greatly simplified and much more interactive experience for these expert users. I’m no HCI expert, but I’ve learned a thing or two over the years, and one of the important ones was the need for synergy between architecture and HCI design.
 

Finally, code that supports highly interactive user interfaces is non-trivial to say the least. Jeremy brought this point up and suggested using design patterns like MVP with a healthy dose of unit tests. I couldn’t agree more, well, yes I could. Even if you use the next generation patterns of Passive View and Supervising Controller, the Dependency Injection development style, and the Command Object pattern, it will not be enough! I’m seeing, in real time, what happens to a project that utilizes all the appropriate patterns, manage their dependencies well, decouple fervently with events, and keep their code clean at all times but doesn’t require/encourage developers to write unit tests. It is a stability nightmare. If you have a complex system to build with intricate logic as to what can be activated when, or any long list of detailed requirements in terms of user interaction, ignore unit tests at your peril. Having a testable design is a great first step, but if you don’t go and test, you’ve negated quite a lot of its benefits.
 

I hope that that didn’t amount to just a bunch of over-tired, jet-lagged, incoherent babbling, but I’ve been waiting to get it off my chest and now seemed like just the time to do so.

More information:


Usability is Timeless, and things that are still broken with usability today.



   


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“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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