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  • Vermeidung von SOA Anti-Patterns mittels AIA

    - by Hans Viehmann
    Gerade ist mir ein White Paper des Enterprise Architecture Teams in die Hände gefallen, das sich mit SOA Anti-Patterns befasst. Es ist zwar kein AIA Paper im eigentlichen Sinne, aber mit AIA hat man natürlich eine gute Unterstützung darin, die dort beschriebenen Fehler zu vermeiden. Das White Paper behandelt Themen wie: Vermeidung von SOA Silos SOA Reifegrad und Projekt-Management Ausuferndes Service Portfolio Umgang mit Referenz-Architekturen EAI 2.0 - Punkt-zu-Punkt Integration auf offenen Standards Ein Link auf das Dokument ist unten angefügt - viel Vergnügen bei der Lektüre ... Oracle White Paper: SOA Anti-Patterns.

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  • New Whitepaper: Best Practices for Gathering EBS Database Statistics

    - by Elke Phelps (Oracle Development)
    Most Oracle Applications DBAs and E-Business Suite users understand the importance of accurate database statistics.  Missing, stale or skewed statistics can adversely affect performance.  Oracle E-Business Suite statistics should only be gathered using FND_STATS or the Gather Statistics concurrent request. Gathering statistics with DBMS_STATS or the desupported ANALYZE command may result in suboptimal executions plans for E-Business Suite. Our E-Business Suite Performance Team has been busy implementing and testing new features for gathering statistics using FND_STATS in Oracle E-Business Suite databases.  The new features and guidelines for when and how to gather statistics are published in the following whitepaper: Best Practices for Gathering Statistics with Oracle E-Business Suite (Note 1586374.1) The new white paper details the following options for gathering statistics using FND_STATS and the Gather Statistics concurrent request:: History Mode - backup existing statistics prior to gather new statistics GATHER_AUTO Option - gather statistics for tables based upon % change Histograms - collect statistics for histograms AUTO Sampling - use the new FND_STATS feature that supports the AUTO option for using AUTO sample size Extended Statistics - use the new FND_STATS feature that supports the creation of column groups and automatic statistics collection on the column groups when table statistics are gathered Incremental Statistics - gather incremental statistics for partitioned tables The new white paper also includes examples and performance test cases for the following: Extended Optimizer Statistics Incremental Statistics Gathering Concurrent Statistics Gathering This white paper includes details about the standalone Oracle E-Business Suite Release 11i and 12 patches that are required to take advantage of this new functionality. Your feedback is welcome We would be very interested in hearing about your experiences with these new options for gathering statistics.  Please feel free to post your comments here or drop us a line privately.Related Oracle OpenWorld 2013 Session Getting Optimal Performance from Oracle E-Business Suite (CON8485) Related My Oracle Support Notes Collecting Statistics with Oracle EBS 11i and R12 (Note 368252.1) Non-EBS Related Blogs, White Papers and My Oracle Support Notes  Oracle Optimizer Blog Understanding Optimizer Statistic (white paper) Fixed Objects Statistics(GATHER_FIXED_OBJECTS_STATS) Considerations (Note 798257.1)

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  • XNA running slow when making a texture

    - by Anthony
    I'm using XNA to test an image analysis algorithm for a robot. I made a simple 3D world that has a grass, a robot, and white lines (that are represent the course). The image analysis algorithm is a modification of the Hough line detection algorithm. I have the game render 2 camera views to a render target in memory. One camera is a top down view of the robot going around the course, and the second camera is the view from the robot's perspective as it moves along. I take the rendertarget of the robot camera and convert it to a Color[,] so that I can do image analysis on it. private Color[,] TextureTo2DArray(Texture2D texture, Color[] colors1D, Color[,] colors2D) { texture.GetData(colors1D); for (int x = 0; x < texture.Width; x++) { for (int y = 0; y < texture.Height; y++) { colors2D[x, y] = colors1D[x + (y * texture.Width)]; } } return colors2D; } I want to overlay the results of the image analysis on the robot camera view. The first part of the image analysis is finding the white pixels. When I find the white pixels I create a bool[,] array showing which pixels were white and which were black. Then I want to convert it back into a texture so that I can overlay on the robot view. When I try to create the new texture showing which ones pixels were white, then the game goes super slow (around 10 hz). Can you give me some pointers as to what to do to make the game go faster. If I comment out this algorithm, then it goes back up to 60 hz. private Texture2D GenerateTexturesFromBoolArray(bool[,] boolArray,Color[] colorMap, Texture2D textureToModify) { for(int i =0;i < screenWidth;i++) { for(int j =0;j<screenHeight;j++) { if (boolArray[i, j] == true) { colorMap[i+(j*screenWidth)] = Color.Red; } else { colorMap[i + (j * screenWidth)] = Color.Transparent; } } } textureToModify.SetData<Color>(colorMap); return textureToModify; } Each Time I run draw, I must set the texture to null, so that I can modify it. public override void Draw(GameTime gameTime) { Vector2 topRightVector = ((SimulationMain)Game).spriteRectangleManager.topRightVector; Vector2 scaleFactor = ((SimulationMain)Game).config.scaleFactorScreenSizeToWindow; this.spriteBatch.Begin(); // Start the 2D drawing this.spriteBatch.Draw(this.textureFindWhite, topRightVector, null, Color.White, 0, Vector2.Zero, scaleFactor, SpriteEffects.None, 0); this.spriteBatch.End(); // Stop drawing. GraphicsDevice.Textures[0] = null; } Thanks for the help, Anthony G.

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  • PHP array taking up too much memory

    - by Dylan Taylor
    I have a multidimensional array. The array itself is fine. My problem is that the script takes up monster amounts of memory, and since I'm running this on my MAMP install on my iBook G4, my computer freezes up. Below is the full script. $query = "SELECT * FROM posts ORDER BY id DESC LIMIT 10"; $result = mysql_query($query); $posts = array(); while($row = mysql_fetch_array($result)){ $posts[$row["id"]]['post_id'] = $row["id"]; $posts[$row["id"]]['post_title'] = $row["title"]; $posts[$row["id"]]['post_text'] = $row["text"]; $posts[$row["id"]]['post_tags'] = $row["tags"]; $posts[$row["id"]]['post_category'] = $row["category"]; foreach ($posts as $post) { echo $post["post_id"]; } Is there a workaround that still achieves my goal (to export the MySQL query rows to an array)? -Dylan

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  • PHP array taking up to much memory

    - by Dylan Taylor
    I have a multidimensional array. The array itself is fine. My problem is that the script takes up monster amounts of memory, and since I'm running this on my MAMP install on my iBook G4, my computer freezes up. Below is the full script. $query = "SELECT * FROM posts ORDER BY id DESC LIMIT 10"; $result = mysql_query($query); $posts = array(); while($row = mysql_fetch_array($result)){ $posts[$row["id"]]['post_id'] = $row["id"]; $posts[$row["id"]]['post_title'] = $row["title"]; $posts[$row["id"]]['post_text'] = $row["text"]; $posts[$row["id"]]['post_tags'] = $row["tags"]; $posts[$row["id"]]['post_category'] = $row["category"]; foreach ($posts as $post) { echo $post["post_id"]; } Is there a workaround that still achieves my goal (to export the MySQL query rows to an array)? -Dylan

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  • Comparison of phrases containing the same word in Google Trends

    - by alisia123
    If I compare three phrases in google trends : house sale house white house I get the following numbers: house - 91 sale house - 3 white house - 2 The question is: Is "sale house" and "white house" already included in the number 91? It is an important question, because if it is true, than: house_except_sale_house + sale_house = 91 sale_house = 3 Which means I have to compare 88 and 3, if I compare "house" and "sale house"

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  • Onsite Interview : QA Engineer with more Emphasis on Java Skills

    - by coolrockers2007
    Hello I'm having a onsite interview for QA engineer with Startup. While phone interview the person said he would want to test my JAVA, JUnit and SQL skills on white board with more importance on Object-oriented skills, So what all can i questions can i expect ? One more important issue : How do i overcome the fear of White board interview ?. I'm very bad at White board sessions, i get fully tensed. Please suggest me tips to overcome my jinx

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  • Read SQL Server Reporting Services Overview

    - by Editor
    Read an excellent, 14-page, general overview of Microsoft SQL Server 2008 Reporting Services entitled White Paper: Reporting Services in SQL Server 2008. Download the White Paper. (360 KB Microsoft Word file) White Paper: Reporting Services in SQL Server 2008 Microsoft SQL Server 2008 Reporting Services provides a complete server-based platform that is designed to support a wide variety [...]

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  • How can I change my "Desktop bar"?

    - by d_Joke
    The problem: In Gnome 3.4 when I click the main menu, it's white. The text of the menu is also white. Original text: I have a problem. When I installed the new version of Gnome (3.4) the "Desktop bar" (I'm sorry, I don't know what's the real name of that bar, but is the bar on the top on Ubuntu 11.10) every time I click on the username icon, or the battery, etc., the menu comes on gray or white and the letters are white. I know maybe this is a stupid question but it annoys me. Besides, my username doest not appear on the login screen. I tried to reset my settings, I delete gnome, and check the Unsettings and CompizConfig but the problem is still there. Maybe I miss something on the process of looking on any configuration tool but I don't think so... Sorry if the question is something basic or even stupid but I'm new on Ubuntu and I'm experimenting whit it.

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  • WPF4 Unleashed - how does converting child elements work?

    - by Kapol
    In chapter 2 of the book WPF4 Unleashed the author shows an example of how XAML processes type conversion. He states that <SolidColorBrush>White</SolidColorBrush> is equivalent to <SolidColorBrush Color="White"/> , because a string can be converted into a SolidColorBrush object. But how is that enough? It doesn't make sense to me. How does XAML know to which property should the value White be assigned?

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  • Natural Search Engine Optimization - Don't "Game the System" Or You Will Get Banned!

    When focusing on natural search engine optimization, it is important that you keep the process "white hat." You see, when it comes to SEO, there are basically three schools of thought: White hat, Gray hat, and Black hat. As you can probably infer, white hat is following the rules, gray hat is a little in between, and black hat is going against parameters that Google and other major search engines have set for ethical SEO practices.

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  • Why is 1px sometimes 2px when specified in Android XML?

    - by Daniel Lew
    I've got a desire for a one-pixel divider line, just for looks. I thought I could accomplish this using a View of height 1px, with a defined background. However, I'm getting some very odd behavior on different devices - sometimes the 1px ends up as 2px. Take this sample layout for example: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <View android:layout_width="fill_parent" android:layout_height="1px" android:background="@android:color/white" android:layout_marginBottom="4dp" /> <View android:layout_width="fill_parent" android:layout_height="1px" android:background="@android:color/white" android:layout_marginBottom="4dp" /> <View android:layout_width="fill_parent" android:layout_height="1px" android:background="@android:color/white" android:layout_marginBottom="4dp" /> <View android:layout_width="fill_parent" android:layout_height="1px" android:background="@android:color/white" android:layout_marginBottom="4dp" /> <View android:layout_width="fill_parent" android:layout_height="1px" android:background="@android:color/white" android:layout_marginBottom="4dp" /> <View android:layout_width="fill_parent" android:layout_height="1px" android:background="@android:color/white" android:layout_marginBottom="4dp" /> <View android:layout_width="fill_parent" android:layout_height="1px" android:background="@android:color/white" android:layout_marginBottom="4dp" /> </LinearLayout> When run on my G1, this comes out fine. But on the Nexus One, it alternates between 1px lines and 2px lines. Does anyone know where this is going awry? Why does Android sometimes make 1px into 2px?

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  • What's a good AJAX Autocomplete Plugin for jQuery?

    - by Murat Ayfer
    I usually use jQuery as my JS library on my sites, and I would like to stick with it since I'm familiar with it. I need to implement an AJAX autocomplete, mainly for suggesting search results. Here are a few I have found: Dylan Verheul's version Jörn Zaefferer's version A modification of Dylan Verheul's version If you have tried any of these plugins, were you happy with them? Which one do you think is the most (and easily) customizable?

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  • Shortest Path algorithm of a different kind

    - by Ram Bhat
    Hey guys, Lets say you have a grid like this (made randomly) Now lets say you have a car starting randomly from one of the while boxes, what would be the shortest path to go through each one of the white boxes? you can visit each white box as many times as you want and cant Jump over the black boxes. The black boxes are like walls. In simple words you can move from white box to white box only.. You can move in any direction, even diagonally.

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  • Ajax Tabs implementation problem .

    - by SmartDev
    Hi , I have Implement ajax tabs and i have four tabs in it . In the four tabs i have four grid views with paging and sorting .The tabs are looking good i can see the grid ,but the problem is my first tab sorting works fine, where if i click on any other tab and click on the grid it goes to my first tab again . One more thing i want to change the background color of each tab. Can anyone help please here is my source code: <asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server"> <asp:ScriptManager ID="ScMMyTabs" runat="server"> </asp:ScriptManager> <cc1:TabContainer ID="TCMytabs" ActiveTabIndex="0" runat="server"> <cc1:TabPanel ID="TpMyreq" runat="server" CssClass="TabBackground" HeaderText="My request"> <ContentTemplate> <table> <tr> <td> <asp:Button ID="btnexportMyRequestCsu" runat="server" Text="Export To Excel" CssClass="LabelDisplay" OnClick="btnexportMyRequestCsu_Click" /> </td> </tr> <tr> <td> <asp:GridView ID="GdvMyrequest" runat="server" CssClass="Mytabs" BackColor="White" BorderColor="White" BorderStyle="Ridge" BorderWidth="2px" CellPadding="3" CellSpacing="1" GridLines="None" OnPageIndexChanging="GdvMyrequest_PageIndexChanging" OnSorting="GdvMyrequest_Sorting" EmptyDataText="No request found for this user"> <RowStyle BackColor="#DEDFDE" ForeColor="Black" /> <FooterStyle BackColor="#C6C3C6" ForeColor="Black" /> <PagerStyle BackColor="Control" ForeColor="Gray" HorizontalAlign="Left" /> <SelectedRowStyle BackColor="#9471DE" Font-Bold="True" ForeColor="White" /> <HeaderStyle BackColor="#4A3C8C" Font-Bold="True" ForeColor="#E7E7FF" /> <PagerSettings Position="TopAndBottom" /> <Columns> <asp:TemplateField> <HeaderTemplate> Row No </HeaderTemplate> <ItemTemplate> <%# Container.DataItemIndex + 1 %> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> </td> </tr> <tr> <td> <asp:Label ID="lblmessmyrequestAhk" runat="server" CssClass="labelmess"></asp:Label> </td> </tr> </table> </ContentTemplate> </cc1:TabPanel> <cc1:TabPanel ID="TpMyPaymentCc" runat="server" HeaderText="Payments Credit Card" > <ContentTemplate> <table> <tr> <td> <asp:GridView ID="GdvmypaymentsCc" runat="server" CssClass="Mytabs" BackColor="White" BorderColor="White" BorderStyle="Ridge" BorderWidth="2px" CellPadding="3" CellSpacing="1" GridLines="None" OnPageIndexChanging="GdvmypaymentsCc_PageIndexChanging" OnSorting="GdvmypaymentsCc_Sorting" EmptyDataText="No Data"> <RowStyle BackColor="#DEDFDE" ForeColor="Black" /> <FooterStyle BackColor="#C6C3C6" ForeColor="Black" /> <PagerStyle BackColor="Control" ForeColor="Gray" HorizontalAlign="Left" /> <SelectedRowStyle BackColor="#9471DE" Font-Bold="True" ForeColor="White" /> <HeaderStyle BackColor="#4A3C8C" Font-Bold="True" ForeColor="#E7E7FF" /> <PagerSettings Position="TopAndBottom" /> </asp:GridView> </td> </tr> <tr> <td> <asp:Label ID="lblmessmypaymentsCsu" runat="server" CssClass="labelmess"></asp:Label> </td> </tr> </table> </ContentTemplate> </cc1:TabPanel> <cc1:TabPanel ID="TpMyPaymentsCk" runat="server" HeaderText="Payments Check" > <ContentTemplate> <asp:GridView ID="GdvmypaymentsCk" runat="server" CssClass="Mytabs" BackColor="White" BorderColor="White" BorderStyle="Ridge" BorderWidth="2px" CellPadding="3" CellSpacing="1" GridLines="None" OnPageIndexChanging="GdvmypaymentsCk_PageIndexChanging" OnSorting="GdvmypaymentsCk_Sorting" EmptyDataText="No Data"> <RowStyle BackColor="#DEDFDE" ForeColor="Black" /> <FooterStyle BackColor="#C6C3C6" ForeColor="Black" /> <PagerStyle BackColor="Control" ForeColor="Gray" HorizontalAlign="Left" /> <SelectedRowStyle BackColor="#9471DE" Font-Bold="True" ForeColor="White" /> <HeaderStyle BackColor="#4A3C8C" Font-Bold="True" ForeColor="#E7E7FF" /> <PagerSettings Position="TopAndBottom" /> </asp:GridView> </ContentTemplate> </cc1:TabPanel> <cc1:TabPanel ID="TpMyCalls" runat="server" HeaderText="Calls" > <ContentTemplate> <table> <tr> <td> <asp:GridView ID="GdvSelectcallsP" runat="server" CssClass="Mytabs" BackColor="White" BorderColor="White" BorderStyle="Ridge" BorderWidth="2px" CellPadding="3" CellSpacing="1" GridLines="None" OnPageIndexChanging="GdvSelectcallsP_PageIndexChanging" OnRowDataBound="GdvSelectcallsP_RowDataBound" OnSorting="GdvSelectcallsP_Sorting" > <RowStyle BackColor="#DEDFDE" ForeColor="Black" /> <FooterStyle BackColor="#C6C3C6" ForeColor="Black" /> <PagerStyle BackColor="#C6C3C6" ForeColor="Black" HorizontalAlign="Right" /> <SelectedRowStyle BackColor="#9471DE" Font-Bold="True" ForeColor="White" /> <HeaderStyle BackColor="#4A3C8C" Font-Bold="True" ForeColor="#E7E7FF" /> <Columns> <asp:TemplateField> <HeaderTemplate> Row No </HeaderTemplate> <ItemTemplate> <%# Container.DataItemIndex + 1 %> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> </td> </tr> <tr> <td> <asp:Label ID="lblmessselectcallsAhkP" runat="server" CssClass="labelmess"></asp:Label> </td> </tr> </table> </ContentTemplate> </cc1:TabPanel> </cc1:TabContainer> </asp:Content>

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  • CQRS &ndash; Questions and Concerns

    - by Dylan Smith
    I’ve been doing a lot of learning on CQRS and Event Sourcing over the last little while and I have a number of questions that I haven’t been able to answer. 1. What is the benefit of CQRS when compared to a typical DDD architecture that uses Event Sourcing and properly captures intent and behavior via verb-based commands? (other than Scalability) 2. When using CQRS what do you do with complex query-based logic? I’m going to elaborate on #1 in this blog post and I’ll do a follow-up post on #2. I watched through Greg Young’s video on the business benefits of CQRS + Event Sourcing and first let me say that I thought it was an excellent presentation that really drives home a lot of the benefits to this approach to architecture (I watched it twice in a row I enjoyed it so much!). But it didn’t answer some of my questions fully (I wish I had been there to ask these of Greg in person!). So let me pick apart some of the points he makes and how they relate to my first question above. I’m completely sold on the idea of event sourcing and have a clear understanding of the benefits that it brings to the table, so I’m not going to question that. But you can use event sourcing without going to a CQRS architecture, so my main question is around the benefits of CQRS + Event Sourcing vs Event Sourcing + Typical DDD architecture Architecture with Event Sourcing + Commands on Left, CQRS on Right Greg talks about how the stereotypical architecture doesn’t support DDD, but is that only because his diagram shows DTO’s coming up from the client. If we use the same diagram but allow the client to send commands doesn’t that remove a lot of the arguments that Greg makes against the stereotypical architecture? We can now introduce verbs into the system. We can capture intent now (storing it still requires event sourcing, but you can implement event sourcing without doing CQRS) We can create a rich domain model (as opposed to an anemic domain model) Scalability is obviously a benefit that CQRS brings to the table, but like Greg says, very few of the systems we create truly need significant scalability Greg talks about the ability to scale your development efforts. He says CQRS allows you to split the system into 3 parts (Client, Domain/Commands, Reads) and assign 3 teams of developers to work on them in parallel; letting you scale your development efforts by 3x with nearly linear gains. But in the stereotypical architecture don’t you already have 2 separate modules that you can split your dev efforts between: The client that sends commands/queries and receives DTO’s, and the Domain which accepts commands/queries, and generates events/DTO’s. If this is true it’s not really a 3x scaling you achieve with CQRS but merely a 1.5x scaling which while great doesn’t sound nearly as dramatic (“I can do it with 10 devs in 12 months – let me hire 5 more and we can have it done in 8 months”). Making the Query side “stupid simple” such that you can assign junior developers (or even outsource it) sounds like a valid benefit, but I have some concerns over what you do with complex query-based logic/behavior. I’m going to go into more detail on this in a follow-up blog post shortly. He also seemed to focus on how “stupid-simple” it is doing queries against the de-normalized data store, but I imagine there is still significant complexity in the event handlers that interpret the events and apply them to the de-normalized tables. It sounds like Greg suggests that because we’re doing CQRS that allows us to apply Event Sourcing when we otherwise wouldn’t be able to (~33:30 in the video). I don’t believe this is true. I don’t see why you wouldn’t be able to apply Event Sourcing without separating out the Commands and Queries. The queries would just operate against the domain model instead of the database. But you’d still get the benefits of Event Sourcing. Without CQRS the queries would only be able to operate against the current state rather than the event history, but even in CQRS the domain behaviors can only operate against the current state and I don’t see that being a big limiting factor. If some query needs to operate against something that is not captured by the current state you would just have to update the domain model to capture that information (no different than if that statement were made about a Command under CQRS). Some of the benefits I do see being applicable are that your domain model might end up being simpler/smaller since it only needs to represent the state needed to process commands and not worry about the reads (like the Deactivate Inventory Item and associated comment example that Greg provides). And also commands that can be handled in a Transaction Script style manner by the command handler simply generating events and not touching the domain model. It also makes it easier for your senior developers to focus on the command behavior and ignore the queries, which is usually going to be a better use of their time. And of course scalability. If anybody out there has any thoughts on this and can help educate me further, please either leave a comment or feel free to get in touch with me via email:

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  • CQRS - Benefits

    - by Dylan Smith
    Thanks to all the comments and feedback from the last post I think I have a better understanding now of the benefits of CQRS (separate from the benefits of Event Sourcing). I’m going to try and sum it up here, and point out some areas where I could still use some advice: CQRS Benefits Sounds like the primary benefit of CQRS as an architecture is it allows you to create a simpler domain model by sucking out everything related to queries. I can definitely see the benefit to this, in general the domain logic related to commands is the high-value behavior in the software, but the logic required to service the queries would add a lot of low-value “noise” to the domain model that would dilute the high-value (command) behavior – sorting, paging, filtering, pre-fetch paths, etc. Also the most appropriate domain structure for implementing commands might not be the most optimal for implementing queries. To paraphrase Greg, this usually results in a domain model that is mediocre at both, piss-poor at one, or more likely piss-poor at both commands and queries. Not only will you be able to simplify your domain model by pulling out all the query logic, but at least a handful of commands in most systems will probably be “pass-though” type commands with little to no logic that just generate events. If these can be implemented directly in the command-handler and never touch the domain model, this allows you to slim down the domain model even more. Also, if you were to do event sourcing without CQRS, you no longer have a database containing the current state (only the domain model would) which makes it difficult (or impossible) to support ad-hoc querying and/or reporting that is common in most business software. Of course CQRS provides some great scalability benefits, not only scalability but I have to assume that it provides extremely low latency for most operations, especially if you have an asynchronous event bus. I know Greg says that you get a 3x scaling (Commands, Queries, Client) of your ability to perform parallel development, but IMHO, it seems like it only provides 1.5x scaling since even without CQRS you’re going to have your client loosely coupled to your domain - which is still a great benefit to be able to realize. Questions / Concerns If all the queries against an aggregate get pulled out to the Query layer, what if the only commands for that aggregate can be handled in a “pass-through” manner with the command handler directly generating events. Is it possible to have an aggregate that isn’t modeled in the domain model? Are there any issues or downsides to this? I know in the feedback from my previous posts it was suggested that having one domain model handling both commands and queries requires implementing a lot of traversals between objects that wouldn’t be necessary if it was only servicing commands. My question is, do you include traversals in your domain model based on the needs of the code, or based on the conceptual domain model? If none of my Commands require a Customer.Orders traversal, but the conceptual domain includes the concept of a set of orders belonging to a customer – should I model that in my domain model or not? I like the idea of using the Query side of the architecture as a place to put junior devs where the risk of them screwing something up has minimal impact. But I’m not sold on the idea that you can actually outsource it. Like I said in one of my comments on my previous post, the code to handle a query and generate DTO’s is going to be dead simple, but the code to process events and apply them to the tables on the query side is going to require a significant amount of domain knowledge to know which events to listen for to update each of the de-normalized tables (and what changes need to be made when each event is processed). I don’t know about everybody else, but having Indian/Russian/whatever outsourced developers have to do anything that requires significant domain knowledge has never been successful in my experience. And if you need to spec out for each new query which events to listen to and what to do with each one, well that’s probably going to be just as much work to document as it would be to just implement it. Greg made the point in a comment that doing an aggregate query like “Total Sales By Customer” is going to be inefficient if you use event sourcing but not CQRS. I don’t understand why that would be the case. I imagine in that case you’d simply have a method/property on the Customer object that calculated total sales for that customer by enumerating over the Orders collection. Then the application services layer would generate DTO’s off of the Customers collection that included say the CustomerID, CustomerName, TotalSales, or whatever the case may be. As long as you use a snapshotting implementation, I don’t see why that would be anymore inefficient in a DDD+Event Sourcing implementation than in a typical DDD implementation. Like I mentioned in my last post I still have some questions about query logic that haven’t been answered yet, but before I start asking those I want to make sure I have a strong grasp on what benefits CQRS provides.  My main concern with the query logic was that I know I could just toss it all into the query side, but I was concerned that I would be losing the benefits of using CQRS in the first place if I did that.  I want to elaborate more on this though with some example situations in an upcoming post.

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  • Software Engineering Practices &ndash; Different Projects should have different maturity levels

    - by Dylan Smith
    I’ve had a lot of discussions at the office lately about the drastically different sets of software engineering practices used on our various projects, if what we are doing is appropriate, and what factors should you be considering when determining what practices are most appropriate in a given context. I wanted to write up my thoughts in a little more detail on this subject, so here we go: If you compare any two software projects (specifically comparing their codebases) you’ll often see very different levels of maturity in the software engineering practices employed. By software engineering practices, I’m specifically referring to the quality of the code and the amount of technical debt present in the project. Things such as Test Driven Development, Domain Driven Design, Behavior Driven Development, proper adherence to the SOLID principles, etc. are all practices that you would expect at the mature end of the spectrum. At the other end of the spectrum would be the quick-and-dirty solutions that are done using something like an Access Database, Excel Spreadsheet, or maybe some quick “drag-and-drop coding”. For this blog post I’m going to refer to this as the Software Engineering Maturity Spectrum (SEMS). I believe there is a time and a place for projects at every part of that SEMS. The risks and costs associated with under-engineering solutions have been written about a million times over so I won’t bother going into them again here, but there are also (unnecessary) costs with over-engineering a solution. Sometimes putting multiple layers, and IoC containers, and abstracting out the persistence, etc is complete overkill if a one-time use Access database could solve the problem perfectly well. A lot of software developers I talk to seem to automatically jump to the very right-hand side of this SEMS in everything they do. A common rationalization I hear is that it may seem like a small trivial application today, but these things always grow and stick around for many years, then you’re stuck maintaining a big ball of mud. I think this is a cop-out. Sure you can’t always anticipate how an application will be used or grow over its lifetime (can you ever??), but that doesn’t mean you can’t manage it and evolve the underlying software architecture as necessary (even if that means having to toss the code out and re-write it at some point…maybe even multiple times). My thoughts are that we should be making a conscious decision around the start of each project approximately where on the SEMS we want the project to exist. I believe this decision should be based on 3 factors: 1. Importance - How important to the business is this application? What is the impact if the application were to suddenly stop working? 2. Complexity - How complex is the application functionality? 3. Life-Expectancy - How long is this application expected to be in use? Is this a one-time use application, does it fill a short-term need, or is it more strategic and is expected to be in-use for many years to come? Of course this isn’t an exact science. You can’t say that Project X should be at the 73% mark on the SEMS and expect that to be helpful. My point is not that you need to precisely figure out what point on the SEMS the project should be at then translate that into some prescriptive set of practices and techniques you should be using. Rather my point is that we need to be aware that there is a spectrum, and that not everything is going to be (or should be) at the edges of that spectrum, indeed a large number of projects should probably fall somewhere within the middle; and different projects should adopt a different level of software engineering practices and maturity levels based on the needs of that project. To give an example of this way of thinking from my day job: Every couple of years my company plans and hosts a large event where ~400 of our customers all fly in to one location for a multi-day event with various activities. We have some staff whose job it is to organize the logistics of this event, which includes tracking which flights everybody is booked on, arranging for transportation to/from airports, arranging for hotel rooms, name tags, etc The last time we arranged this event all these various pieces of data were tracked in separate spreadsheets and reconciliation and cross-referencing of all the data was literally done by hand using printed copies of the spreadsheets and several people sitting around a table going down each list row by row. Obviously there is some room for improvement in how we are using software to manage the event’s logistics. The next time this event occurs we plan to provide the event planning staff with a more intelligent tool (either an Excel spreadsheet or probably an Access database) that can track all the information in one location and make sure that the various pieces of data are properly linked together (so for example if a person cancels you only need to delete them from one place, and not a dozen separate lists). This solution would fall at or near the very left end of the SEMS meaning that we will just quickly create something with very little attention paid to using mature software engineering practices. If we examine this project against the 3 criteria I listed above for determining it’s place within the SEMS we can see why: Importance – If this application were to stop working the business doesn’t grind to a halt, revenue doesn’t stop, and in fact our customers wouldn’t even notice since it isn’t a customer facing application. The impact would simply be more work for our event planning staff as they revert back to the previous way of doing things (assuming we don’t have any data loss). Complexity – The use cases for this project are pretty straightforward. It simply needs to manage several lists of data, and link them together appropriately. Precisely the task that access (and/or Excel) can do with minimal custom development required. Life-Expectancy – For this specific project we’re only planning to create something to be used for the one event (we only hold these events every 2 years). If it works well this may change (see below). Let’s assume we hack something out quickly and it works great when we plan the next event. We may decide that we want to make some tweaks to the tool and adopt it for planning all future events of this nature. In that case we should examine where the current application is on the SEMS, and make a conscious decision whether something needs to be done to move it further to the right based on the new objectives and goals for this application. This may mean scrapping the access database and re-writing it as an actual web or windows application. In this case, the life-expectancy changed, but let’s assume the importance and complexity didn’t change all that much. We can still probably get away with not adopting a lot of the so-called “best practices”. For example, we can probably still use some of the RAD tooling available and might have an Autonomous View style design that connects directly to the database and binds to typed datasets (we might even choose to simply leave it as an access database and continue using it; this is a decision that needs to be made on a case-by-case basis). At Anvil Digital we have aspirations to become a primarily product-based company. So let’s say we use this tool to plan a handful of events internally, and everybody loves it. Maybe a couple years down the road we decide we want to package the tool up and sell it as a product to some of our customers. In this case the project objectives/goals change quite drastically. Now the tool becomes a source of revenue, and the impact of it suddenly stopping working is significantly less acceptable. Also as we hold focus groups, and gather feedback from customers and potential customers there’s a pretty good chance the feature-set and complexity will have to grow considerably from when we were using it only internally for planning a small handful of events for one company. In this fictional scenario I would expect the target on the SEMS to jump to the far right. Depending on how we implemented the previous release we may be able to refactor and evolve the existing codebase to introduce a more layered architecture, a robust set of automated tests, introduce a proper ORM and IoC container, etc. More likely in this example the jump along the SEMS would be so large we’d probably end up scrapping the current code and re-writing. Although, if it was a slow phased roll-out to only a handful of customers, where we collected feedback, made some tweaks, and then rolled out to a couple more customers, we may be able to slowly refactor and evolve the code over time rather than tossing it out and starting from scratch. The key point I’m trying to get across is not that you should be throwing out your code and starting from scratch all the time. But rather that you should be aware of when and how the context and objectives around a project changes and periodically re-assess where the project currently falls on the SEMS and whether that needs to be adjusted based on changing needs. Note: There is also the idea of “spectrum decay”. Since our industry is rapidly evolving, what we currently accept as mature software engineering practices (the right end of the SEMS) probably won’t be the same 3 years from now. If you have a project that you were to assess at somewhere around the 80% mark on the SEMS today, but don’t touch the code for 3 years and come back and re-assess its position, it will almost certainly have changed since the right end of the SEMS will have moved farther out (maybe the project is now only around 60% due to decay). Developer Skills Another important aspect to this whole discussion is around the skill sets of your architects and lead developers. When talking about the progression of a developers skills from junior->intermediate->senior->… they generally start by only being able to write code that belongs on the left side of the SEMS and as they gain more knowledge and skill they become capable of working at a higher and higher level along the SEMS. We all realize that the learning never stops, but eventually you’ll get to the point where you can comfortably develop at the right-end of the SEMS (the exact practices and techniques that translates to is constantly changing, but that’s not the point here). A critical skill that I’d love to see more evidence of in our industry is the most senior guys not only being able to work at the right-end of the SEMS, but more importantly be able to consciously work at any point along the SEMS as project needs dictate. An even more valuable skill would be if you could make the conscious decision to move a projects code further right on the SEMS (based on changing needs) and do so in an incremental manner without having to start from scratch. An exercise that I’m planning to go through with all of our projects here at Anvil in the near future is to map out where I believe each project currently falls within this SEMS, where I believe the project *should* be on the SEMS based on the business needs, and for those that don’t match up (i.e. most of them) come up with a plan to improve the situation.

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  • Meta package / quick reference for string manipulation commands?

    - by Dylan McCall
    The latest version of the Scribes text editor lets us select some text, hit Alt+X, and then run an arbitrary command. For example, I can run the sort command and the selected text is replaced appropriately. This is quite useful but I am also not very well-versed in awk and the like. Is there something I can grab that will provide more of these commands like sort? Maybe a package with a whole bunch of handy, task-specific string manipulation commands?

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  • Running Unity 2d - Does not work on actual system but works fine in VM

    - by Dylan
    So I'm running Ubuntu 10.10 and I cannot get Unity 2d to work with my system. This is particularly frustrating as it works just fine in all the VMs I've tested it on. I actually really like Unity and I want to get to know it (in part) before Ubuntu 11.04. I checked Synaptic and it looks like everything's there. The only thing not installed are dev libs and so on. Should I install those as well? Obviously the difference between my system and a VM is that the VM is running off a basically brand new OS. I only use VMs to test new stuff out and remake them often, so my only guess is that I have something installed on my system that is preventing Unity from running. Any thoughts?

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  • PrairieDevCon &ndash; Slide Decks

    - by Dylan Smith
    PrairieDevCon 2010 was an awesome time.  Learned a lot, and had some amazing conversations.  You guys even managed to convince me that NoSQL databases might actually be useful after all.   For those interested here’s my slide decks from my two sessions: Agile In Action Database Change Management With Visual Studio

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  • How can I get something like Nautilus's "spatial" behaviour in 11.10 and later?

    - by Dylan McCall
    Until recently, Nautilus had an optional "spatial" mode as an alternative to its usual browser mode. Users could enable it by opening Nautilus's preferences and selecting "Open each folder in its own window." Choosing this option resulted in a stripped down interface, and folders would always open in the same place on the screen. It looked something like this: That checkbox is still there, but it doesn't do the same thing: while every folder opens in a new window, those windows are all the same size and positioned the same way. Nautilus doesn't restore the size and position of each folder, which is what spatial mode was all about. This difference really shows if someone opens a folder in a new window, and then opens the same folder again. Nautilus will create another window instead of focusing the existing window. I help someone who is currently using Ubuntu 10.04, and he will be upgrading to 12.04 in the future. He is very comfortable with Nautilus's spatial behaviour and I think he would be disappointed to lose it. Is there an alternative file manager, or perhaps some less obvious option, that will give him an interface similar to the one he is comfortable with?

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  • Rawr Code Clone Analysis&ndash;Part 0

    - by Dylan Smith
    Code Clone Analysis is a cool new feature in Visual Studio 11 (vNext).  It analyzes all the code in your solution and attempts to identify blocks of code that are similar, and thus candidates for refactoring to eliminate the duplication.  The power lies in the fact that the blocks of code don't need to be identical for Code Clone to identify them, it will report Exact, Strong, Medium and Weak matches indicating how similar the blocks of code in question are.   People that know me know that I'm anal enthusiastic about both writing clean code, and taking old crappy code and making it suck less. So the possibilities for this feature have me pretty excited if it works well - and thats a big if that I'm hoping to explore over the next few blog posts. I'm going to grab the Rawr source code from CodePlex (a World Of Warcraft gear calculator engine program), run Code Clone Analysis against it, then go through the results one-by-one and refactor where appropriate blogging along the way.  My goals with this blog series are twofold: Evaluate and demonstrate Code Clone Analysis Provide some concrete examples of refactoring code to eliminate duplication and improve the code-base Here are the initial results:   Code Clone Analysis has found: 129 Exact Matches 201 Strong Matches 300 Medium Matches 193 Weak Matches Also indicated is that there was a total of 45,181 potentially duplicated lines of code that could be eliminated through refactoring.  Considering the entire solution only has 109,763 lines of code, if true, the duplicates lines of code number is pretty significant. In the next post we’ll start examining some of the individual results and determine if they really do indicate a potential refactoring.

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