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• Opinions on sensor / reading / alert database design

  - by Mark

  I've asked a few questions lately regarding database design, probably too many ;-) However I beleive I'm slowly getting to the heart of the matter with my design and am slowly boiling it down. I'm still wrestling with a couple of decisions regarding how "alerts" are stored in the database. In this system, an alert is an entity that must be acknowledged, acted upon, etc. Initially I related readings to alerts like this (very cut down) : - [Location] LocationId [Sensor] SensorId LocationId UpperLimitValue LowerLimitValue [SensorReading] SensorReadingId Value Status Timestamp [SensorAlert] SensorAlertId [SensorAlertReading] SensorAlertId SensorReadingId The last table is associating readings with the alert, because it is the reading that dictate that the sensor is in alert or not. The problem with this design is that it allows readings from many sensors to be associated with a single alert - whereas each alert is for a single sensor only and should only have readings for that sensor associated with it (should I be bothered that the DB allows this though?). I thought to simplify things, why even bother with the SensorAlertReading table? Instead I could do this: [Location] LocationId [Sensor] SensorId LocationId [SensorReading] SensorReadingId SensorId Value Status Timestamp [SensorAlert] SensorAlertId SensorId Timestamp [SensorAlertEnd] SensorAlertId Timestamp Basically I'm not associating readings with the alert now - instead I just know that an alert was active between a start and end time for a particular sensor, and if I want to look up the readings for that alert I can do. Obviously the downside is I no longer have any constraint stopping me deleting readings that occurred during the alert, but I'm not sure that the constraint is neccessary. Now looking in from the outside as a developer / DBA, would that make you want to be sick or does it seem reasonable? Is there perhaps another way of doing this that I may be missing? Thanks. EDIT: Here's another idea - it works in a different way. It stores each sensor state change, going from normal to alert in a table, and then readings are simply associated with a particular state. This seems to solve all the problems - what d'ya think? (the only thing I'm not sure about is calling the table "SensorState", I can't help think there's a better name (maybe SensorReadingGroup?) : - [Location] LocationId [Sensor] SensorId LocationId [SensorState] SensorStateId SensorId Timestamp Status IsInAlert [SensorReading] SensorReadingId SensorStateId Value Timestamp There must be an elegant solution to this!

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• Using Moq at Blend design time

  - by adrian hara

  This might be a bit out there, but suppose I want to use Moq in a ViewModel to create some design time data, like so: public class SomeViewModel { public SomeViewModel(ISomeDependency dependency) { if (IsInDesignMode) { var mock = new Mock<ISomeDependency>(); dependency = mock.Object; // this throws! } } } The mock could be set up to do some stuff, but you get the idea. My problem is that at design-time in Blend, this code throws an InvalidCastException, with the message along the lines of "Unable to cast object of type 'Castle.Proxies.ISomeDependencyProxy2b3a8f3188284ff0b1129bdf3d50d3fc' to type 'ISomeDependency'." While this doesn't necessarily look to be Moq related but Castle related, I hope the Moq example helps ;) Any idea why that is? Thanks!

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• Where did System.Design go?

  - by Nilbert

  I am making a C# project in which I am using ScintillaNet, and it says: The referenced assembly "ScintillaNet" could not be resolved because it has a dependency on "System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" which is not in the currently targeted framework ".NETFramework,Version=v4.0,Profile=Client". Please remove references to assemblies not in the targeted framework or consider retargeting your project. I tried adding a reference to System.Design, but it doesn't exist in my list. Do I need to download it somewhere? I have MS Visual Studio 10.

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• OOP Design for an Economy

  - by waiwai933

  Not sure where to start, so I'm just going to plow in. Let's say I'm trying to represent an economy in OOP. A basic design I've come up with is: class Person{ int $money; // Money someone has in wallet/purse int $bank_account_id; function getAmountOfMoney() function addMoney($amountToAdd) function subtractMoney($amountToSubtract) } class BankAccount{ int $money; // Money in Bank Account int $interest_per_year; function giveInterest() function depositMoney() // Calls $person->subtractMoney() function withdrawMoney() // Calls $person->addMoney() } Are there any design flaws here?

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• C# Language Design: explicit interface implementation of an event

  - by ControlFlow

  Small question about C# language design :)) If I had an interface like this: interface IFoo { int Value { get; set; } } It's possible to explicitly implement such interface using C# 3.0 auto-implemented properties: sealed class Foo : IFoo { int IFoo.Value { get; set; } } But if I had an event in the interface: interface IFoo { event EventHandler Event; } And trying to explicitly implement it using field-like event: sealed class Foo : IFoo { event EventHandler IFoo.Event; } I will get the following compiler error: error CS0071: An explicit interface implementation of an event must use event accessor syntax I think that field-like events is the some kind of dualism for auto-implemented properties. So my question is: what is the design reason for such restriction done?

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• Capitalizing on JavaScript's prototypal inheritance

  - by keithjgrant

  JavaScript has a class-free object system in which objects inherit properties directly from other objects. This is really powerful, but it is unfamiliar to classically trained programmers. If you attempt to apply classical design patterns directly to JavaScript, you will be frustrated. But if you learn to work with JavaScript's prototypal nature, your efforts will be rewarded. ... It is Lisp in C's clothing. -Douglas Crockford What does this mean for a game developer working with canvas and HTML5? I've been looking over this question on useful design patterns in gaming, but prototypal inheritance is very different than classical inheritance, and there are surely differences in the best way to apply some of these common patterns. For example, classical inheritance allows us to create a moveableEntity class, and extend that with any classes that move in our game world (player, monster, bullet, etc.). Sure, you can strongarm JavaScript to work that way, but in doing so, you are kind of fighting against its nature. Is there a better approach to this sort of problem when we have prototypal inheritance at our fingertips?

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• Domain-driven design with Zend

  - by mik

  This question is a continuation of my previous question here http://stackoverflow.com/questions/2122850/zend-models-architecture (big thanks to Bill Karwin). I've made some reading including this article http://weierophinney.net/matthew/archives/202-Model-Infrastructure.html and this question http://stackoverflow.com/questions/373054/how-to-properly-create-domain-using-zend-framework Now I understand, what domain driven design is. But examples are still very simple and poor. They are based on one table and one model. Now, my question is: do they use Domain Model Design in real-world PHP projects? I've been looking for some good documentation about this, but I haven't found anything good enough, that explains how to manage several tables and transfer them to Domain Objects. As long as I know, there is Hibernate library, that has this features in Java, but what should I use in PHP (Zend Framework)?

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• Design from scratch - building classes

  - by Tony

  Hi All, I've started a new project where I'm writing a WPF business application, but I'm having trouble with the design. The database was easy to put together, but I'm not sure how I have to go about the designing the application itself. The main thing that I find hard is the code design. I've decided that the MVVM pattern is very applicable for this application, but how do I go about deciding what classes to build and how things go from there? Does anyone have some guidelines I could use? This is a standard business application that just stores and retrieves data. Some data queries will also need to be performed.

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• Service design or access to another process

  - by hotyi

  I have a cache service,it's works as .net remoting, i want to create another windows service to clean up the that cache service by transfer the objects from cache to files. because they are in separate process, is their any way i could access that cache service or do i have to expose a method from the cache service to do that clean up work? the "clean up" means i want to serialize the object from Cache to file and these saved file will be used for further process. let me explain this application more detail. the application is mainly a log service to log all the coming request and these request will be saved to db for further data mining. we have 2 design for this log system 1) use MSMQ, but seems it's performance is not good enough, we don't use it. 2) we design a cache service, each request will be saved into the cache, and we need another function to clean up the cache by serialize the object to file.

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• Domain Specific Languages (DSL) and Domain Driven Design (DDD)

  - by bovium

  What is the differences and similarities between Domain Specific Languages (DSL) and Domain Driven Design (DDD)?

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• Web design process with CSS - during or after?

  - by SyaZ

  Which is the better practice? Add CSS during web designing you can see the result (or close) as early as possible and make required changes. You also know how many divs or spans you might need (eg to make curved cross-browser hover background). But as you add more and more components to the page sometimes things get hack-ish as you need to patch here and there to get the exact design required. Add CSS after finishing page design you can see the page overall structure as it is well, without styles. You get to see how accessible your site is, and modify it right away if it's not good enough (unlike the former case where you may break multiple CSS rules). Plus after you finished it, you only need to spend most of the time to alter only the CSS file, which is good to get the momentum going. Granted I have never tried the latter approach, but am seriously considering it for my next project if I can see convincing reasons -- or if it's no good at all. Thanks.

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• UI Design Choices and How to Implement Them

  - by AKRamkumar

  I am making an application that is a dashboard/widget host. I am using MEF to load the plugins and I have a ui Concept Idea like this: http://i42.tinypic.com/scb6nd.png Is this a good design choice? How would I implement the Navigation? Is there any Design Patter you would reccomend for this? Note: My contract interface is this. public interface IDashboardPlugin { public string Name{get;} public string Description{get;} public string Author{get;} public UIElement UI{get;} }

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• Name for Osherove's modified singleton pattern?

  - by Kazark

  I'm pretty well sold on the "singletons are evil" line of thought. Nevertheless, there are limited occurrences when you want to limit the creation of an object. Roy Osherove advises, If you're planning to use a singleton in your design, separate the logic of the singleton class and the logic that makes it a singleton (the part that initializes a static variables, for example) into two separate classes. That way, you can keep the single responsibility principle (SRP) and also have a way to override singleton logic. (The Art of Unit Testing 261-262) This pattern still perpetuates the global state. However, it does result in a testable design, so it seems to me to be a good pattern for mitigating the damage of a singleton. However, Osherove does not give a name to this pattern; but naming a pattern, according to the Gang of Four, is important: Naming a pattern immediately increases our design vocabulary. It lets us design at a higher level of abstraction. (3) Is there a standard name for this pattern? It seems different enough from a standard singleton to deserve a separate name. Decoupled Singleton, perhaps?

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• Ecommerce database design looking for good book

  - by meyosef

  Hi I looking for good book about E-commerce database design. Thanks

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• Java: design problem with private-final-int-value and empty constructor

  - by HH

  $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; //DUE to new Klowledge: Design Problem //I think having an empty constructor like this // is an design problem, shall I remove it? What do you think? // When to use an empty constructor? InitInt(){} public static void main(String[] args) { InitInt test = new InitInt(); System.out.println(test.getRight()); } public int getRight(){return right;} } Initialization problem with Constructor InitInt{ // Still the error, "may not be initialized" // How to initialise it? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } }

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• Looking for some Feedback on a DB Design

  - by zSysop

  I'm currently working on a ticketing system which allows our users to submit tickets based on their own needs. i.e. if Department "A" is submitting a ticket they can have certain types of problem categories (such as "Supplies" or "Printer") along with details pertaining to the chosen category. I have laid out a partial db design and i was looking for some feedback on it. I've never built a system from the ground up by myself so i'm a little bit nervous. here's my a draft version of my db design Issues Table Id | CreatedBy | CreateDate | Status | Owner | AssignedTo | AssignmentDate | ----------------------------------------------------------------------------- EquipmentIssueDetails Table Id | IssueId | Serial # | Make | Model | .... --------------------------------------------- SupplyIssueDetails Table Id | IssueId | SupplyId | ItemId | QTY | UnitOfMeasurement ------------------------------------------------------------- NetworkIssueDetails Table Id | IssueId | Supervisor | Details | ------------------------------------------------------------- Notes Table Id | IssueId | Note | CreatedBy | CreateDate ------------------------------------------------------------- Thanks in advance

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• User control attributes at design-time

  - by ciscoheat

  I'm testing a simple User Control in Visual Studio 2008: A Panel named Wrapper with some controls inside. Can Visual Studio handle this at design time? public partial class TestControl : System.Web.UI.UserControl { [Description("Css class of the div around the control.")] [CssClassProperty] public string CssClass { get { return Wrapper.CssClass; } set { Wrapper.CssClass = value; } } } When setting the CssClass property, it doesn't update the css of the Panel at design time. Am I hoping for too much?

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• Must all AI states be able to react to any event?

  - by Prog

  FSMs implemented with the State design pattern are a common way to design AI agents. I am familiar with the State design pattern and know how to implement it. How is this used in games to design AI agents? Consider a simplified class Monster, representing an AI agent: class Monster { State state; // other fields omitted public void update(){ // called every game-loop cycle state.execute(this); } public void setState(State state){ this.state = state; } // irrelevant stuff omitted } There are several State subclasses implementing execute() differently. So far, classic State pattern. AI agents are subject to environmental effects and other objects communicating with them. For example, an AI agent might tell another AI agent to attack (i.e. agent.attack()). Or a fireball might tell an AI agent to fall down. This means that the agent must have methods such as attack() and fallDown(), or commonly some message receiving mechanism to understand such messages. With an FSM, the current State of the agent should be the one taking care of such method calls - i.e. the agent delegates to the current state upon every event. Is this correct? If correct, how is this done? Are all states obligated by their superclass to implement methods such as attack(), fallDown() etc., so the agent can always delegate to them on almost every event? Or is it done in some other way?

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• Should I think about switching to another platform as a .Net developer? [closed]

  - by A. Karimi

  I’ve been a developer for about 10 years and I’ve almost worked on Microsoft stack. At the last several years I’ve been introduced to some good practices such as IoC and other primary design patterns. Now I feel so much comfortable using these patterns and concepts and I’m very angry why we didn’t do that earlier! They exist and used by many developers since more than 5 years ago but why I and many of my colleagues began using them a little later. As you may know Java developers are more ahead in these fields (concepts, patterns and …) than .Net developers. Am I right? Now the question is, “Why we (as .NET developers) weren’t ahead so much? Isn’t it because we are using Microsoft stack?”. I know ALT.NET but why we are trying make a closed ecosystem open and finding alternatives for Microsoft Echo Chamber, while there are natively open ecosystems like Java!? I've always liked most of the Microsoft works very much but I’m worried about this issue. I am even ask myself should I move to another platform?

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• Database design efficiency with 1 to many relationships limited 1 to 3

  - by Joe

  This is in mysql, but its a database design issue. If you have a one to many relationship, like a bank customer to bank-accounts, typically you would have the table that records the bank-account information have a foreign key that keeps track of the relationship between account and customer. Now this follows the 3rd normal form thing and is a widely accepted way of doing it. Now lets say that you are going to limit a user to only having 3 accounts. The current database implementation will support this and nothing would need to change. But another way to do this would have 3 coloms in the account table that have the id of the 3 respective accounts in them. By the way this violates 1st normal form of db design. The question is what would be the advantage and disadvantages of having the user account relationship recored in this way over the traditional?

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• What is the best design to this class?

  - by HPT

  assume this class: public class Logger { static TextWriter fs = null; public Logger(string path) { fs = File.CreateText(path); } public static void Log(Exception ex) { ///do logging } public static void Log(string text) { ///do logging } } and I have to use this like: Logger log = new Logger(path); and then use Logger.Log() to log what I want. the question is: is this a good design? to instantiate a class and then always call it's static method? any suggestion yield in better design is appreciated.

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• Resources for dashboard app backend design

  - by Nix

  I am looking for examples of code/data/infrastructure design for a dashboard-style webapp. I am designing an interface for staff and faculty at a university to access departmental resources and be alerted of cyclical processes, events, deadlines, etc. Technologies I am working with: apache tomcat 6 and a mySQL database, JSP (including JSTL), bootstrap 3, and javascript/jquery. I have basic experience most of these technologies building smaller web apps but was hoping someone could direct me towards a book or other resource that discusses how to design the db architecture (and maybe how to template) for a dashboard, esp. for something like a notification systems. Any suggestions?

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• Design Documents for Python/Django?

  - by british_trader

  After working on a Django project for a while, I now have to do some design documents for it (UML type stuff). However the code doesn't have classes, but instead uses views.py with modules in it... What would be the best way to show the design of my application from the initial __init__.py, to the urls.py where the HTML requests are then filtered to the specific urls.py in each of the packages and then handled by the views.py? i.e. django-app urls.py views.py settings.py manager.py __init__.py django-package urls.py views.py

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• Inventory Management OOP design

  - by rgamber

  This was an OOP design and implementation interview question, which I came across on glassdoor.com. Design and implement a inventory management system to minimize the number of missed delivery dates while keeping costs to the company low. Of course there is no right answer to this, but I am not sure I understand the question correctly and am wondering what would be a good answer. Is this as simple as creating an undirected graph with nodes as the delivery points, and edges having weights as the cost of the delivery, and then use a single-source-shortest-path algorithm (like Dijkstras, or Bellman-Ford) on the graph? Not sure if this type of question should be asked here,so let me know and I will delete it.

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• What do I need to know to design a language and write a interpreter for it?

  - by alFReD NSH

  I know this question has been asked and even there are thousands of books and articles about it. But the problem is that there are too many, and I don't know are they good enough, I have to design a language and write a interpreter for it. The base language is javascript (using nodejs) but it's ok if the compiler was written in another language that I can use from node. I had done a research about compiler compilers in JS, there is jison (Bison implementaion in JS), waxeye, peg.js. I decided to give jison a try, due to the popularity and its being used by coffee script, so it should be able to cover my language too. The grammar definition syntax is similar to bison. But when I tried read the bison manual it seemed very hard to understand for me. And I think it's because I don't know a lot of things about what I'm doing. Like I don't what is formal language theory. I am experienced in Javascript (I'm more talented in JS than most average programmers). And also know basic C and C++ (not much experience but can write a working code for basic things). I haven't had any formal education, so I may not be familiar with some software engineering and computer science principles. Though everyday I try to grasp a lot of articles and improve. So I'm asking if you know any good book or article that can help me. Please also write why the resource you're suggesting is good. --update-- The language I'm trying to create, is not really complicated. All it has is expressions (with or without units), comparisons and logical operators. There are no functions, loops, ... The goal is to create a language that non-programmers can easily learn. And to write customized validations and calculations.

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