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• Database Design Primay Key, ID vs String

  - by LnDCobra

  Hi, I am currently planning to develop a music streaming application. And i am wondering what would be better as a primary key in my tables on the server. An ID int or a Unique String. Methods 1: Songs Table: SongID(int), Title(string), Artist*(string), Length(int), Album*(string) Genre Table Genre(string), Name(string) SongGenre: SongID*(int), Genre*(string) Method 2 Songs Table: SongID(int), Title(string), ArtistID*(int), Length(int), AlbumID*(int) Genre Table GenreID(int), Name(string) SongGenre: SongID*(int), GenreID*(int) Key: Bold = Primary Key, Field* = Foreign Key I'm currently designing using method 2 as I believe it will speed up lookup performance and use less space as an int takes a lot less space then a string. Is there any reason this isn't a good idea? Is there anything I should be aware of?

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• Database design grouping contacts by lists and companies

  - by Serge

  Hi, I'm wondering what would be the best way to group contacts by their company. Right now a user can group their contacts by custom created lists but I'd like to be able to group contacts by their company as well as store the contact's position (i.e. Project Manager of XYZ company). Database wise this is what I have for grouping contacts into lists contact [id_contact] [int] PK NOT NULL, [lastName] [varchar] (128) NULL, [firstName] [varchar] (128) NULL, ...... contact_list [id_contact] [int] FK, [id_list] [int] FK, list [id_list] [int] PK [id_user] [int] FK [list_name] [varchar] (128) NOT NULL, [description] [TEXT] NULL Should I implement something similar for grouping contacts by company? If so how would I store the contact's position in that company and how can I prevent data corruption if a user modifies a contact's company name. For instance John Doe changed companies but the other co-workers are still in the old company. I doubt that will happen often (might not even happen at all) but better be safe than sorry. I'm also keeping an audit trail so in a way the contact would still need to be linked to the old company as well as the new one but without confusing what company he's actually working at the moment. I hope that made sense... Has anyone encountered such a problem? UPDATE Would something like this make sense contact_company [id_contact_company] [int] PK [id_contact] [int] FK [id_company] [int] FK [contact_title] [varchar] (128) company [id_company] [int] PK NOT NULL, [company_name] [varchar] (128) NULL, [company_description] [varchar] (300) NULL, [created_date] [datetime] NOT NULL This way a contact can work for more than one company and contacts can be grouped by companies

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• Learning OOP Design

  - by waiwai933

  I've read Head First Java, and I understand how OOP works. Here's my problem: I'm a PHP programmer, and while I've used OOP in PHP, I'm having trouble figuring out what should be an object and what methods to give it. For example, let's say I have a app that allows people to log in and edit a document. Why should the document be an object if there will ever only be one instance? Should I give the deleteDocument() method to the document object or the admin object? The document is the one being deleted, but the admin is the one performing the action. So my real question is, coming from a procedural background, how do I figure out what should be objects and what should have what methods?

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• Is an "infinite" iterator bad design?

  - by Adamski

  Is it generally considered bad practice to provide Iterator implementations that are "infinite"; i.e. where calls to hasNext() always(*) return true? Typically I'd say "yes" because the calling code could behave erratically, but in the below implementation hasNext() will return true unless the caller removes all elements from the List that the iterator was initialised with; i.e. there is a termination condition. Do you think this is a legitimate use of Iterator? It doesn't seem to violate the contract although I suppose one could argue it's unintuitive. public class CyclicIterator<T> implements Iterator<T> { private final List<T> l; private Iterator it; public CyclicIterator<T>(List<T> l) { this.l = l; this.it = l.iterator(); } public boolean hasNext() { return !l.isEmpty(); } public T next() { T ret; if (!hasNext()) { throw new NoSuchElementException(); } else if (it.hasNext()) { ret = it.next(); } else { it = l.iterator(); ret = it.next(); } return ret; } public void remove() { it.remove(); } }

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• MVC design question for forms

  - by kenny99

  Hi, I'm developing an app which has a large amount of related form data to be handled. I'm using a MVC structure and all of the related data is represented in my models, along with the handling of data validation from form submissions. I'm looking for some advice on a good way to approach laying out my controllers - basically I will have a huge form which will be broken down into manageable categories (similar to a credit card app) where the user progresses through each stage/category filling out the answers. All of these form categories are related to the main relation/object, but not to each other. Does it make more sense to have each subform/category as a method in the main controller class (which will make that one controller fairly massive), or would it be better to break each category into a subclass of the main controller? It may be just for neatness that the second approach is better, but I'm struggling to see much of a difference between either creating a new method for each category (which communicates with the model and outputs errors/success) or creating a new controller to handle the same functionality. Thanks in advance for any guidance!

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• Database Design Composite Keys

  - by guazz

  I am going to use a contrived example: one headquarter has one-or-many contacts. A contact can only belong to one headquarter. TableName = Headquarter Column 0 = Id : Guid [PK] Column 1 = Name : nvarchar(100) Column 2 = IsAnotherAttribute: bool TableName = ContactInformation Column 0 = Id : Guid [PK] Column 1 = HeadquarterId: Guid [FK] Column 2 = AddressLine1 COlumn 3 = AddressLine2 Column 4 = AddressLine3 I would like some help setting the table primary keys and foreign keys here? How does the above look? Should I use a composite key for ContactInformation on [Column 0 and Column1]? Is it ok to use surrogate key all of the time?

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• Subroutine & GoTo design

  - by sub

  I have a strange question concerning subroutines: As I'm creating a minimal language and I don't want to add high-level loops like while or for I was planning on just adding gotos to keep it Turing-Complete. Now I thought, eww - gotos - I wouldn't want to program in that language if I had to use gotos so often. So I thought about adding subroutines instead. I see the difference as the following: gotos Go to (captain obvious) a previously defined point and continue executing the program from there. Leads to hardly understandable and buggy code, I think that's a fact. subroutines Similiar: You define their starting point somewhere, as you call them the program jumps there - but the subroutine can go back to the point it was called from with return. Okay. Why didn't I just add the more function-like, nice looking subroutines? Because: In order to make return work if I call subroutines from within subroutines from within other subroutines, I'd have to use a stack containing the point where the currently running subroutine came from at top. That would then mean that I would, if I create loops using the subroutines, end up with an extremely memory-eating, overflowing stack with return locations. Not good. Don't think of my subroutines as functions. They are just gotos that return to the point they were called from, they don't actually give back values like the return x; statement in nearly all today's languages. Now to my actual questions: How can I solve the above problem with the stack overflow on loops with subroutines? Do I have to add a separate goto language construct without the return option? Assembler doesn't have loops but as I have seen myJumpPoint:, jnz, jz, retn. That means to me that there must also be a stack containing all the return locations. Am I right with that? What about long running loops then? Don't they overflow the stack/eat memory then? Am I getting the retn symbol in assembler totally wrong? If yes, please explain it to me.

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• Flexible design - customizable entity model, UI and workflow

  - by Ngm

  Hi All, I want to achieve the following aspects in the software I am building: 1. Customizable entity model 2. Customizable UI 3. Customizable workflow I have thought about an approach to achieve this, I want you to review this and make suggestions: Entity objects should be plain objects and will hold just data Separate Entity model and DB Schema by using an framework (like NHibernate?). This will allow easy modification of entity objects. Business logic to fetch/modify entities has to be granular enough so that they can be invoked as part of the workflow. Business objects should not hold any state, and hence will contain only static methods The workflow will decide depending upon the "state" of an entity/entities which methods on business object/objects to invoke. The workflow should obtain the results of the processing and then pass on the business objects to the appropriate UI screen. The UI screen has to contain instructions about how to display a given entity/entites. Possibly the UI has to be generated dynamically based on a set of UI instructions. (like XUL) What do you think about this approach? Suggest which existing frameworks (like NHiberante, Window Workflow) fit into this model, so that I will not spend time on coding these frameworks Also suggest is there any asp.net framework that can generate dynamic asp.net ajax pages based on a set of UI instructions (like Mozilla XUL)? I have recently been exploring Apache Ofbiz and was impressed by its ability to customize most areas of the application: UI, workflow, entities. Is there any similar (not necessarily an ERP system) application developed in C#/.Net which offers a similar level of customization? I am looking for examples of applications developed in C# that are highly customizable in terms of UI, Workflow and Entity Model

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• using PHP for "Fluid" design(using viewport resolution)

  - by Jreeter

  I need some opinions on using PHP to make completely "scalable" websites.. For instance, using viewport resolution and resizing images, applying dynamic css styles..... In my mind doing this just add's to the complexity and should not be done, it should be fixed or fluid using strictly css and no server-side languages to generate layouts based on the device size.. I need some input and maybe some philosophy on why using this approach is not used at all..

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• Design a GUI browser to view a tree

  - by iamrohitbanga

  I have a large tree. I want to be able to visualize it using a GUI tool. I want the ability to pan and zoom the tree image so that i can focus on part of the tree. Is there an existing tool to achieve this? If not i would like to write a small tool for myself to be able to do this. what is the simplest way of doing this? what computer language should i use? the image should look something like http://upload.wikimedia.org/wikipedia/commons/d/df/Binary_tree.png I should be able to zoom and pan the image.

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• Buddy List: Relational Database Table Design

  - by huntaub

  So, the modern concept of the buddy list: Let's say we have a table called Person. Now, that Person needs to have many buddies (of which each buddy is also in the person class). The most obvious way to construct a relationship would be through a join table. i.e. buddyID person1_id person2_id 0 1 2 1 3 6 But, when a user wants to see their buddy list, the program would have to check the column 'person1_id' and 'person2_id' to find all of their buddies. Is this the appropriate way to implement this kind of table, or would it be better to add the record twice.. i.e. buddyID person1_id person2_id 0 1 2 1 2 1 So that only one column has to be searched. Thanks in advance.

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• Does this inheritance design belong in the database?

  - by Berryl

  === CLARIFICATION ==== The 'answers' older than March are not answers to the question in this post! Hello In my domain I need to track allocations of time spent on Activities by resources. There are two general types of Activities of interest - ones base on a Project and ones based on an Account. The notion of Project and Account have other features totally unrelated to both each other and capturing allocations of time, and each is modeled as a table in the database. For a given Allocation of time however, it makes sense to not care whether the allocation was made to either a Project or an Account, so an ActivityBase class abstracts away the difference. An ActivityBase is either a ProjectActivity or an AccountingActivity (object model is below). Back to the database though, there is no direct value in having tables for ProjectActivity and AccountingActivity. BUT the Allocation table needs to store something in the column for it's ActivityBase. Should that something be the Id of the Project / Account or a reference to tables for ProjectActivity / Accounting? How would the mapping look? === Current Db Mapping (Fluent) ==== Below is how the mapping currently looks: public class ActivityBaseMap : IAutoMappingOverride<ActivityBase> { public void Override(AutoMapping<ActivityBase> mapping) { //mapping.IgnoreProperty(x => x.BusinessId); //mapping.IgnoreProperty(x => x.Description); //mapping.IgnoreProperty(x => x.TotalTime); mapping.IgnoreProperty(x => x.UniqueId); } } public class AccountingActivityMap : SubclassMap<AccountingActivity> { public void Override(AutoMapping<AccountingActivity> mapping) { mapping.References(x => x.Account); } } public class ProjectActivityMap : SubclassMap<ProjectActivity> { public void Override(AutoMapping<ProjectActivity> mapping) { mapping.References(x => x.Project); } } There are two odd smells here. Firstly, the inheritance chain adds nothing in the way of properties - it simply adapts Projects and Accounts into a common interface so that either can be used in an Allocation. Secondly, the properties in the ActivityBase interface are redundant to keep in the db, since that information is available in Projects and Accounts. Cheers, Berryl ==== Domain ===== public class Allocation : Entity { ... public virtual ActivityBase Activity { get; private set; } ... } public abstract class ActivityBase : Entity { public virtual string BusinessId { get; protected set; } public virtual string Description { get; protected set; } public virtual ICollection<Allocation> Allocations { get { return _allocations.Values; } } public virtual TimeQuantity TotalTime { get { return TimeQuantity.Hours(Allocations.Sum(x => x.TimeSpent.Amount)); } } } public class ProjectActivity : ActivityBase { public virtual Project Project { get; private set; } public ProjectActivity(Project project) { BusinessId = project.Code.ToString(); Description = project.Description; Project = project; } }

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• Following Domain Driven Design with MVVM/WPF

  - by msfanboy

  Hello, I have plain POCOs here and as INotifyPropertyChanged is a Interface for the Views need its implemented in the ViewModel not the Model. Now I want to show validation errors in the View beside every textbox the user typed in data. I do not want to implemented the IDataErrorInfo interface in my Models because lets assume I am not allowed to touch them as they come from another Service/Supplier. I do not want to put my IsCustomerFirstNameLenthValid Method into the Model because I could not have access to it or I just dont want to pollute my Models with interface`s having nothing to do there! How can I validate my naked POCO`s in the ViewModel and forward the results to the View by showing validation errors ?

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• Is factory method proper design for my problem?

  - by metdos

  Hello Everyone, here is my problem and I'm considering to use factory method in C++, what are your opinions ? There are a Base Class and a lot of Subclasses. I need to transfer objects on network via TCP. I will create objects in first side, and using this object I will create a byte array TCP message, and send it to other side. On the other side I will decompose TCP message, I will create object and I will add this object to a polymorphic queue.

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• Database design for heavy timed data logging

  - by user293995

  Hi, I have an application where I receive each data 40.000 rows. I have 5 million rows to handle (500 Mb MySQL 5.0 database). Actually, thoses rows are stored in the same table = slow to update, hard to backup, ... Which king of scheme is used in such application to allow long term accessibility to the datas without problems with too big tables, easy backup, fast read / write ? Is postgresql better than mysql for such purpose ? Thanks in advance BEst regards

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• Tag, comment, rating, etc. database design

  - by Efe Kaptan

  I want to implement modules such as comment, rating, tag, etc. to my entities. What I thought was: comments_table - comment_id, comment_text entity1 - entitity1_id, entity1_text entity2 - entitity2_id, entity2_text entity1_comments - entity1_id, comment_id entity2_comments - entity2_id, comment_id .... Is this approach correct?

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• DB Design Question

  - by hazimdikenli

  I am designing an Org Chart, model is almost ready and simplified a bit for clarity here. OrgUnit (OrgUnitId, Name, ReportsToOrgUnitId, ...) OrgUnitJobs (OrgUnitJobId, OrgUnitId, JobName, ReportsToOrgUnitJobId, ... ,IsJobGroup) Employee (EmployeeId, ........) OrgUnitJobEmployee (OrgUnitJobId, EmployeeId, AssignedDate, .....,) so I want to know every OrgUnit's ManagerEmployee (should have one), and Employees can have more than one job, but one of them has to be the main job, so I know whats his manager and other stuff. This is going to support a little workflow behind the scnese, so that is why it is not a very simple Org chart Model. so what would you do, would you add properties like (IsManager property to OrgUnitJobs model) or add ManagerOrgUnitJobId to OrgUnitModel. and why? Likewise, for employees would you add IsPrimaryJob property to OrgUnitJobEmployee model, or add PrimaryJobId to Employee Model.

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• Facebook database design?

  - by Marin

  I have always wondered how Facebook designed the friend <- user relation. I figure the user table is something like this: user_email PK user_id PK password I figure the table with user's data (sex, age etc connected via user email I would assume). How does it connect all the friends to this user? Something like this? user_id friend_id_1 friend_id_2 friend_id_3 friend_id_N Probably not. Because the number of users is unknown and will expand.

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• MongoDB Schema Design - Real-time Chat

  - by Nick

  I'm starting a project which I think will be particularly suited to MongoDB due to the speed and scalability it affords. The module I'm currently interested in is to do with real-time chat. If I was to do this in a traditional RDBMS I'd split it out into: Channel (A channel has many users) User (A user has one channel but many messages) Message (A message has a user) The the purpose of this use case, I'd like to assume that there will be typically 5 channels active at one time, each handling at most 5 messages per second. Specific queries that need to be fast: Fetch new messages (based on an bookmark, time stamp maybe, or an incrementing counter?) Post a message to a channel Verify that a user can post in a channel Bearing in mind that the document limit with MongoDB is 4mb, how would you go about designing the schema? What would yours look like? Are there any gotchas I should watch out for?

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• UI Design, incase of numerous situations

  - by The King

  Hi... I'm creating a web form, where in there are around 12-15 Input Fields... You can have a look at the screen and The request is such that depending on the data the user selects in the Gridview and the DropDown list, the appropriate Textboxes and CheckBoxes needs to be displayed. Some times the conditions are very direct, like when the DDL value is "ABC", get only paid amount from the user. Sometime they are so complex like... IF DDL is "DEF" and Selected GPMS value is between 1000-2000, calculate the values of allowed, paid etc (using some formula) and the focus should be directed to Page No Field, leaving the other fields open incase user wants to edit... There are around 10-15 conditions like this. As this was done through agile, conditions were being added as and when, and wherever it feels appropriate (DDL on change Event, GridView on selecting change event etc... etc..) After completion, now I see the code has become a big chuck, is growing unmanageably... Now, I'm planning to clear this... From you experience, what you think is the best way to handle this. There is a possibility to add more conditions like this in future... Please let me know, incase you need more information. I'm currently developing this app in C# .Net WindowsForms Edit: Currently there are only three items (The Datagrid, the DDL, the OverrideAmt CheckBox) that change the way other fields behave... Almost all of the conditions will fall between the two situations I mentioned... Mostly they belong to "Enabling/Disabling".. "Setting of Values"... and "Changing Focus" or any combination of these.

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• How should I design my MYSQL table/s?

  - by yaya3

  I built a really basic php/mysql site for an architect that uses one 'projects' table. The website showcases various projects that he has worked on. Each project contained one piece of text and one series of images. Original projects table (create syntax): CREATE TABLE `projects` ( `project_id` int(11) NOT NULL auto_increment, `project_name` text, `project_text` text, `image_filenames` text, `image_folder` text, `project_pdf` text, PRIMARY KEY (`project_id`) ) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=latin1; The client now requires the following, and I'm not sure how to handle the expansions in my DB. My suspicion is that I will need an additional table. Each project now have 'pages'. Pages either contain... One image One "piece" of text One image and one piece of text. Each page could use one of three layouts. As each project does not currently have more than 4 pieces of text (a very risky assumption) I have expanded the original table to accommodate everything. New projects table attempt (create syntax): CREATE TABLE `projects` ( `project_id` int(11) NOT NULL AUTO_INCREMENT, `project_name` text, `project_pdf` text, `project_image_folder` text, `project_img_filenames` text, `pages_with_text` text, `pages_without_img` text, `pages_layout_type` text, `pages_title` text, `page_text_a` text, `page_text_b` text, `page_text_c` text, `page_text_d` text, PRIMARY KEY (`project_id`) ) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=latin1; In trying to learn more about MYSQL table structuring I have just read an intro to normalization and A Simple Guide to Five Normal Forms in Relational Database Theory. I'm going to keep reading! Thanks in advance

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• Partial Classes - are they bad design?

  - by dferraro

  Hello, I'm wondering why the 'partial class' concept even exists in .NET. I'm working on an application and we are reading a (actually very good) book relavant to the development platform we are implementing at work. In the book he provides a large code base /wrapper around the platform API and explains how he developed it as he teaches different topics about the platform development. Anyway, long story short - he uses partial classes, all over the place, as a way to fake multiple inheritence in C# (IMO). Why he didnt just split the classes up into multiple ones and use composition is beyond me. He will have 3 'partial class' files to make up his base class, each w/ 3-500 lines of code... And does this several times in his API. Do you find this justifiable? If it were me, I'd have followed the S.R.P. and created multiple classes to handle different required behaviors, then create a base class that has instances of these classes as members (e.g. composition). Why did MS even put partial class into the framework?? They removed the ability to expand/collapse all code at each scope level in C# (this was allowed in C++) because it was obviously just allowing bad habits - partial class is IMO the same thing. I guess my quetion is: Can you explain to me when there would be a legitimate reason to ever use a partial class? I do not mean this to be a rant / war thread. I'm honeslty looking to learn something here. Thanks

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• How do I normalise this database design?

  - by Ian Roke

  I am creating a rowing reporting and statistics system for a client where I have a structure at the moment similar to the following: ----------------------------------------------------------------------------- | ID | Team | Coaches | Rowers | Event | Position | Time | ----------------------------------------------------------------------------- | 18 | TeamName | CoachName1 | RowerName1 | EventName | 1 | 01:32:34 | | | | CoachName2 | RowerName2 | | | | | | | | RowerName3 | | | | | | | | RowerName4 | | | | ----------------------------------------------------------------------------- This is an example row of data but I would like to expand this out to a Rowers table and Coaches table and so on but I don't know how best to then link that back to the Entries table which is what this is. Has anybody got any words of wisdom they could share with me? Update A Team can have any number of Coaches and Rowers, a Rower can be in many Teams (Team A, B, C etc) and a Team can have many Coaches.

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• website design - graphics files

  - by mb08

  Hi Friends, I have a website to be designed and have most of the material ready with me. I have shortlisted a designer who is ready to start. The question I have is, should I hand over the original .psd graphics files of logo etc to the designer. Is it ok to hand over the .psds or is there any risk in doing so that I should be aware of and cover with an agreement... thanks in advance.. mb

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• alt-tab sort of web design

  - by sureshgl

  I am thinking of designing a web site having multiple related services. For every action of the user in a service there will be some computation going on in each of the other services. I want to display the service in action (chosen by the user) in the middle of the page in enlarged mode and rest of the services as small sized (shrunk) versions around the enlarged mode. The services which are shown in the shrunk version, should actually show what is happening in that service, at run time as if that was the chosen service. A close match to this sort of behavior I know is in Reliance BigTV, where all the small images of all the channels will be going on, and we can choose the one that we want to watch. After choosing that one image will become big and occupy the screen. Please, let me know if I can do some thing like this using css, html, ajax & php.

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