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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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  • 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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  • IoC and Design Time

    - by benPearce
    I have a WPF application which I am using to learn MVVM and IoC. The problem is that the Model used by one of the Views expects to pull one of its dependancies in the constructor from an IoC container. When working on this View in the Visual Studio designer it cannot show the design because an exception is being raised in the model. Is there a way around this? Am I pulling my dependancies in the wrong place in code or is there a way I can pass in constructed dependancies, perhaps through Constructor injection. At present the IoC container is setup in code in App.xaml.cs. The IoC container is a roll-your-own taken from this article on MSDN - http://msdn.microsoft.com/en-us/magazine/cc337885.aspx

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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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  • A good design pattern for almost similar objects

    - by Sam
    Hello, I have two websites that have an almost identical database schema. the only difference is that some tables in one website have 1 or 2 extra fields that the other and vice versa. I wanted to the same Database Access layer classes to will manipulate both websites. What can be a good design pattern that can be used to handle that little difference. for example, I have a method createAccount(Account account) in my DAO class but the implementation will be slightly different between website A and website B. I know design patterns don't depend on the language but FYI i m working with Perl. Thanks

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  • Design pattern for cost calculator app?

    - by Anders Svensson
    Hi, I have a problem that I’ve tried to get help for before, but I wasn’t able to solve it then, so I’m trying to simplify the problem now to see if I can get some more concrete help with this because it is driving me crazy… Basically, I have a working (more complex) version of this application, which is a project cost calculator. But because I am at the same time trying to learn to design my applications better, I would like some input on how I could improve this design. Basically the main thing I want is input on the conditionals that (here) appear repeated in two places. The suggestions I got before was to use the strategy pattern or factory pattern. I also know about the Martin Fowler book with the suggestion to Refactor conditional with polymorphism. I understand that principle in his simpler example. But how can I do either of these things here (if any would be suitable)? The way I see it, the calculation is dependent on a couple of conditions: 1. What kind of service is it, writing or analysis? 2. Is the project small, medium or large? (Please note that there may be other parameters as well, equally different, such as “are the products new or previously existing?” So such parameters should be possible to add, but I tried to keep the example simple with only two parameters to be able to get concrete help) So refactoring with polymorphism would imply creating a number of subclasses, which I already have for the first condition (type of service), and should I really create more subclasses for the second condition as well (size)? What would that become, AnalysisSmall, AnalysisMedium, AnalysisLarge, WritingSmall, etc…??? No, I know that’s not good, I just don’t see how to work with that pattern anyway else? I see the same problem basically for the suggestions of using the strategy pattern (and the factory pattern as I see it would just be a helper to achieve the polymorphism above). So please, if anyone has concrete suggestions as to how to design these classes the best way I would be really grateful! Please also consider whether I have chosen the objects correctly too, or if they need to be redesigned. (Responses like "you should consider the factory pattern" will obviously not be helpful... I've already been down that road and I'm stumped at precisely how in this case) Regards, Anders The code (very simplified, don’t mind the fact that I’m using strings instead of enums, not using a config file for data etc, that will be done as necessary in the real application once I get the hang of these design problems): public abstract class Service { protected Dictionary<string, int> _hours; protected const int SMALL = 2; protected const int MEDIUM = 8; public int NumberOfProducts { get; set; } public abstract int GetHours(); } public class Writing : Service { public Writing(int numberOfProducts) { NumberOfProducts = numberOfProducts; _hours = new Dictionary<string, int> { { "small", 125 }, { "medium", 100 }, { "large", 60 } }; } public override int GetHours() { if (NumberOfProducts <= SMALL) return _hours["small"] * NumberOfProducts; if (NumberOfProducts <= MEDIUM) return (_hours["small"] * SMALL) + (_hours["medium"] * (NumberOfProducts - SMALL)); return (_hours["small"] * SMALL) + (_hours["medium"] * (MEDIUM - SMALL)) + (_hours["large"] * (NumberOfProducts - MEDIUM)); } } public class Analysis : Service { public Analysis(int numberOfProducts) { NumberOfProducts = numberOfProducts; _hours = new Dictionary<string, int> { { "small", 56 }, { "medium", 104 }, { "large", 200 } }; } public override int GetHours() { if (NumberOfProducts <= SMALL) return _hours["small"]; if (NumberOfProducts <= MEDIUM) return _hours["medium"]; return _hours["large"]; } } public partial class Form1 : Form { public Form1() { InitializeComponent(); List<int> quantities = new List<int>(); for (int i = 0; i < 100; i++) { quantities.Add(i); } comboBoxNumberOfProducts.DataSource = quantities; } private void comboBoxNumberOfProducts_SelectedIndexChanged(object sender, EventArgs e) { Service writing = new Writing((int) comboBoxNumberOfProducts.SelectedItem); Service analysis = new Analysis((int) comboBoxNumberOfProducts.SelectedItem); labelWriterHours.Text = writing.GetHours().ToString(); labelAnalysisHours.Text = analysis.GetHours().ToString(); } }

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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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  • Where is the iPhone's Date & Time getting it's time zone list

    - by johnbdh
    I can get a list of time zones with [NSTimeZone knownTimeZoneNames], but that only gives the time zone IDs which include one or 2 cities in each time zone. The Date & Time settings has a great list of cities and I have seen a few other apps that have the same if not similar lookup lists. Where do these lists come from?? I do need to relate a picked city to it's time zone like Date & Time does. Thanks, John

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  • Custom Providers & Design Patterns

    - by Code Sherpa
    Hi. I am using ASP.NET 2.0 and its various providers. I have overridden most of the methods I need and have the following custom providers: ProjectMembershipProvider ProjectProfileProvider ProjectRoleProvider In the design of my project, my intention was to wrap the custom providers in a facade - style design - mixing and matching profiling, membership, and roles in API methods to simplify things for developers. But, I am finding that a lot of the methods in my custom providers don't need to change, really. And, it seems silly to wrap a stand-alone method in another method that does exactly the same thing. So - is my approach wrong? Or, should I allow end - users to instantiate the custom providers when needed and the mix/match api when needed? This seems a bit redundant to me but I can't see another way. Advice appreciated. Thanks.

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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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  • Adding controls dynamically at design time vb.net

    - by chris
    I have been developing some custom smart tags. I am using a DesignerActionMethodItem which gets me to a fired method in code. When I try to hit the controls.Add the control is added but it seems the designer is unaware of it. It is never serialized and it goes away when the form is refreshed in the designer. Any help would be greatly appreciated. I am sort of stuck and google hasn't helped me. Please don't send me anything about smart tags that has nothing to do with adding controls dynamically at design time, I have already read so many looking for this.

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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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  • 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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  • design using a readonly class in c#

    - by edosoft
    Hi Small design question here. I'm trying to develop a calculation app in C#. I have a class, let's call it InputRecord, which holds 100s of fields (multi dimensional arrays) This InputRecordclass will be used in a number of CalculationEngines. Each CalculcationEngine can make changes to a number of fields in the InputRecord. These changes are steps needed for it's calculation. Now I don't want the local changes made to the InputRecord to be used in other CalculcationEngine's classes. The first solution that comes to mind is using a struct: these are value types. However I'd like to use inheritance: each CalculationEngine needs a few fields only relevant to that engine: it's has it's own InputRecord, based on BaseInputRecord. Can anyone point me to a design that will help me accomplish this?

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  • How should I handle "real time" events in an online strategy game?

    - by Hojat Taheri
    Some online strategy games have real time events. For example when you send troops to attack somewhere, the attack happens at the right time in the future. Checking the database again and again to get the list of attacks happening each second would cause heavy load. Is there any technique to achieve this goal? Another example: You want to attack a village 3 hours away, you send troops and the attack occurs 3 hours later. Should there be an script to check the database at each second to run the query at the specified time?

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  • Design patterns and interview question

    - by user160758
    When I was learning to code, I read up on the design patterns like a good boy. Long after this, I started to actually understand them. Design discussions such as those on this site constantly try to make the rules more and more general, which is good. But there is a line, over which it becomes over-analysis starts to feed off itself and as such I think begins to obfuscate the original point - for example the "What's Alternative to Singleton" post and the links contained therein. http://stackoverflow.com/questions/1300655/whats-alternative-to-singleton I say this having been asked in both interviews I’ve had over the last 2 weeks what a singleton is and what criticisms I have of it. I have used it a few times for items such as user data (simple key-value eg. last file opened by this user) and logging (very common i'm sure). I've never ever used it just to have what is essentially global application data, as this is clearly stupid. In the first interview, I reply that I have no criticisms of it. He seemed disappointed by this but as the job wasn’t really for me, I forgot about it. In the next one, I was asked again and, as I wanted this job, I thought about it on the spot and made some objections, similar to those contained in the post linked to above (I suggested use of a factory or dependency injection instead). He seemed happy with this. But my problem is that I have used the singleton without ever using it in this kind of stupid way, which I had to describe on the spot. Using it for global data and the like isn’t something I did then realised was stupid, or read was stupid so didn’t do, it was just something I knew was stupid from the start. Essentially I’m supposed to be able to think of ways of how to misuse a pattern in the interview? Which class of programmers can best answer this question? The best ones? The medium ones? I'm not sure.... And these were both bright guys. I read more than enough to get better at my job but had never actually bothered to seek out criticisms of the most simple of the design patterns like this one. Do people think such questions are valid and that I ought to know the objections off by heart? Or that it is reasonable to be able to work out what other people who are missing the point would do on the fly? Or do you think I’m at least partially right that the question is too unsubtle and that the questions ought to be better thought out in order to make sure only good candidates can answer. PS. Please don’t think I’m saying that I’m just so clever that I know everything automatically - I’ve learnt the hard way like everyone else. But avoiding global data is hardly revolutionary.

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  • Magento Design Patterns

    - by JonB
    Magento, IMHO, represents a PHP system that is built on well thought-out coding principles - reuseable design patterns being one of them. In terms of an example of a PHP system, I think it can be considered pretty cutting edge and therefore worth considering from an architectural point of view. As I understand it, there are many design patterns that are available to the OOP developer. Seeing such patterns being put to use in an open-source system such as Magento allows a developer to view examples of such patterns in real use and in situ, rather than in examples that can sometimes be rather achedemic, and even a little misleading. As such, I am wondering what patterns, other than the ones I have listed below, Magento programmers have used when developing for Magento. As a note, I understand that some of these patterns are in place as a consequence of being built on the Zend Framework, MVC / Front Controller being a couple of them, The obvious ones are: Factory: $product = Mage::getModel('catalog/product'); Singleton: $category = Mage::getSingleton('catalog/session'); Registry: $currentCategory = Mage::registry('current_category');

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  • Subtracting Delphi Time Ranges from a Date Range, Calculate Remaining Time

    - by Anagoge
    I'm looking for an algorithm that will help calculate a workday working time length. It would have an input date range and then allow subtracting partially or completely intersecting time range slices from that date range and the result would be the number of minutes (or the fraction/multiple of a day) left in the original date range, after subtracting out the various non-working time slices. For Example: Input date range: 1/4/2010 11:21 am - 1/5/2010 3:00 pm Subtract out any partially or completely intersecting slices like this: Remove all day Sunday Non-Sundays remove 11:00 - 12:00 Non-Sundays remove time after 5:00 pm Non-Sundays remove time before 8:00 am Non-Sundays remove time 9:15 - 9:30 am Output: # of minutes left in the input date range I don't need anything overly-general. I could hardcode the rules to simplify the code. If anyone knows of sample code or a library/function somewhere, or has some pseudo-code ideas, I'd love something to start with. I didn't see anything in DateUtils, for example. Even a basic function that calculates the number of minutes of overlap in two date ranges to subtract out would be a good start.

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  • Singletons and other design issues

    - by Ahmed Saleh
    I have worked using different languages like C++/Java and currently AS3. Most applications were computer vision, and small 2D computer games. Most companies that I have worked for, they use Singletons in a language like AS3, to retrieve elements or classes in an easy way. Their problem is basically they needs some variables or to call other functions from other classes. In a language like AS3, there is no private constructor, and they write a hacky code to prevent new instances. In Java and C++ I also faced the situation that I need to use other classe's members or to call their functions in different classes. The question is, is there a better or another design, to let other classes interact with each others without using singletons? I feel that composition is the answer, but I need more detailed solutions or design suggestions.

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