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InfoQ Homepage Presentations Command-Query Responsibility Segregation

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Command-Query Responsibility Segregation

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Bio

Udi Dahan is The Software Simplist, an expert on software architecture and design. A Solutions Architecture and Connected Systems MVP 4 years in a row, Mr. Dahan is also one of 33 experts in Europe recognized by the International .NET Association, an author and trainer for the International Association of Software Architects, and an SOA/Web Services/XML Guru recommended by Dr. Dobbs Journal (DDJ).

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Recorded at:

Sep 01, 2010

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Community comments

  • Your message is awaiting moderation. Thank you for participating in the discussion.

    How to change the system if requirements changed for a particular view? For example we need additional data for a particular view that is already exists and the data is already somewhere in other views and core domain, but it is quite complex to retrieve it?

    And the same question about lack of data in domain entities if we already store it in the views. Again we have to do some complex migration from query source to core data storage.

  • View database updates?

    by Dandik M /

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    I really like the concept. We’ve been pushing a lighter version of it in one of our projects.

    None the less, the thirst question that came from almost anyone who we presented the concept to was:

    What about users editing theyr own account information? Let’s say user changes his address, closes browser and then remembers he forgot to change house number. It’s going to be frustrating if he opens his account information and bum – the information he just entered is not there (just because the view database is not yet up to date)!

    Yes this might be a rear use case, but the frustration level as I can imagine might be … well let’s say high.

    What I want to say, the concept is good as long as there are no data updates going on in the system. I can hardly imagine let’s say ERP system without updates, that needs to be reviewed right away after they are done. What is your solution to this scenario?

  • Your message is awaiting moderation. Thank you for participating in the discussion.

    InfoQ should really start uploading the slides separately along with the vids. Even something embedded like scribd if not raw PDFs would be nice. Who has the time to watch every vid?

  • Annoying tone

    by Wouter Vos /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    This guys sounds like he's talking to small children. Very annoying.
    He may have interesting observations on current processes, but we're not stupid, it's not like he's unveiling a big secret here.

  • Thanks a lot.

    by Tobias Juderjahn /

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    Great!

  • Good stuff

    by Dmitry Novoselov /

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    We use pre-calculated views, but very restrictedly. We only do that when we just can't prepare what is needed to be shown to a user in reasonable amount of time. Then we say something like "Oh God, they want it to show in just 10 seconds. We have no choice but to pre-calculate the screen and store it in the database." And we try to avoid pre-calculation doing a lot of caching and other technical tweaks. But it really seems like it should be a default option.

    And if we changed our minds and built another architecture, we wouldn't have to do all those tweaks. I'll definitely try to use more of this approach in my next project.

  • Udi Dahan is not a good researcher

    by Pedro Gonzalez /

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    Udi Dahan is not a good researcher and as other commenters say he does not know what he is talking about.
    He presents many incoherent topics without delivering any value.

  • boring

    by Mohamed Ramadan /

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    man you're boring like F*** !

  • OMG...shoot me!

    by Everett Fitzgibbons /

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    Way to talkative and I fell asleep listening to the presentation. Just get to the points...yawn, yawn

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