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• Functional/nonfunctional requirements VS design ideas

  - by Nicholas Chow

  Problem domain Functional requirements defines what a system does. Non-Functional requirements defines quality attributes of what the system does as a whole.(performance, security, reliability, volume, useability, etc.) Constraints limits the design space, they restrict designers to certain types of solutions. Solution domain Design ideas , defines how the system does it. For example a stakeholder need might be we want to increase our sales, therefore we must improve the usability of our webshop so more customers will purchase, a requirement can be written for this. (problem domain) Design takes this further into the solution domain by saying "therefore we want to offer credit card payments in addition to the current prepayment option". My problem is that the transition phase from requirement to design seems really vague, therefore when writing requirements I am often confused whether or not I incorporated design ideas in my requirements, that would make my requirement wrong. Another problem is that I often write functional requirements as what a system does, and then I also specify in what timeframe it must be done. But is this correct? Is it then a still a functional requirement or a non functional one? Is it better to seperate it into two distinct requirements? Here are a few requirements I wrote: FR1 Registration of Organizer FR1 describes the registration of an Organizer on CrowdFundum FR1.1 The system shall display a registration form on the website. FR1.2 The system shall require a Name, Username, Document number passport/ID card, Address, Zip code, City, Email address, Telephone number, Bank account, Captcha code on the registration form when a user registers. FR1.4 The system shall display an error message containing: “Registration could not be completed” to the subscriber within 1 seconds after the system check of the registration form was unsuccessful. FR1.5 The system shall send a verification email containing a verification link to the subscriber within 30 seconds after the system check of the registration form was successful. FR1.6 The system shall add the newly registered Organizer to the user base within 5 seconds after the verification link was accessed. FR2 Organizer submits a Project FR2 describes the submission of a Project by an Organizer on CrowdFundum - FR2 The system shall display a submit Project form to the Organizer accounts on the website.< - FR2.3 The system shall check for completeness the Name of the Project, 1-3 Photo’s, Keywords of the Project, Punch line, Minimum and maximum amount of people, Funding threshold, One or more reward tiers, Schedule of when what will be organized, Budget plan, 300-800 Words of additional information about the Project, Contact details within 1 secondin after an Organizer submits the submit Project form. - FR2.8 The system shall add to the homepage in the new Projects category the Project link within 30 seconds after the system made a Project webpage - FR2.9 The system shall include in the Project link for the homepage : Name of the Project, 1 Photo, Punch line within 30 seconds after the system made a Project webpage. Questions: FR 1.1 : Have I incorporated a design idea here, would " the system shall have a registration form" be a better functional requirement? F1.2 ,2.3 : Is this not singular? Would the conditions be better written for each its own separate requirement FR 1.4: Is this a design idea? Is this a correct functional requirement or have I incorporated non functional(performance) in it? Would it be better if I written it like this: FR1 The system shall display an error message when check is unsuccessful. NFR: The system will respond to unsuccesful registration form checks within 1 seconds. Same question with FR 2.8 and 2.9. FR2.3: The system shall check for "completeness", is completeness here used ambigiously? Should I rephrase it? FR1.2: I added that the system shall require a "Captcha code" is this a functional requirement or does it belong to the "security aspect" of a non functional requirement. I am eagerly waiting for your response. Thanks!

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• Good resources for language design

  - by Aaron Digulla

  There are lots of books about good web design, UI design, etc. With the advent of Xtext, it's very simple to write your own language. What are good books and resources about language design? I'm not looking for a book about compiler building (like the dragon book) but something that answers: How to create a grammar that is forgiving (like adding optional trailing commas)? Which grammar patterns cause problems for users of a language? How create a compact grammar without introducing ambiguities

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• Design Patterns and their most common uses for them [closed]

  - by cable729

  Possible Duplicate: What are some programming design patterns that are useful in game development? As I'm returning to game dev, I've realized that I've lost a lot of the knowledge I had before. So now I'm looking at design patterns that I can use for my next project. One design pattern that I've seen a lot is the 'composition method,' which uses actors and components. Is that the right name for it? I'd like to look more at this and see what the advantages/pitfalls are. So what design patterns are out there, and what are the advantages/disadvantages to them?

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• How to explain why design choices are good?

  - by Telastyn

  As I've become a better developer, I find that much of my design skill comes more from intuition than mechanical analysis. This is great. It lets me read code and get a feel for it quicker. It lets me translate designs between languages and abstractions much easier. And it let's me get stuff done faster. The downside is that I find it harder to explain to teammates (and worse, management) why a particular design is advantageous; especially teammates that are behind the times on best practices. "This design is more testable!" or "You should favor composition over inheritance." go right over their heads, and lead into the rabbit hole of me trying to clue everyone in to the last decade of software engineering advances. I'll get better at it with practice of course, but in the mean time it involves a lot of wasted time and/or bad design (that will lead to wasted time fixing it later). How can I better explain why a certain design is superior, when the benefits aren't completely obvious to the audience?

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• Help with MVC design pattern?

  - by user3681240

  I am trying to build a java program for user login but I am not sure if my MVC design is accurate. I have the following classes: LoginControl - servlet LoginBean - data holder java class with private variables getters and setters LoginDAO - concrete java class where I am running my SQL queries and doing rest of the logical work. Connection class - java class just to connect to the database view - jsp to display the results html - used for form Is this how you design a java program based on MVC design pattern? Please provide some suggestions?

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• New to Java and Spring. What are some good design principles for an inexperienced java developer like me?

  - by Imtiaz Ahmad

  I am learning Java and have written a few small useful programs. I am new to spring but have managed to understand the concept of dependency injection for decoupling. I'm trying to applying that in my development work in an enterprise setting. What are the 3 most important design patterns I should master (not for interview purposes but ones that I will use every day in as a good java developer)? Also what are some good java design considerations and practices in coding specifically in Java? My goal is write good decoupled and coherent programs that are easy to maintain that don't make me standout as a java rookie. Stuff like not beginning my package names with com. have already made me precariously visible in my team. But they know I have 2 years of coding experience and its not in java.

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• Is this kind of design - a class for Operations On Object - correct?

  - by Mithir

  In our system we have many complex operations which involve many validations and DB activities. One of the main Business functionality could have been designed better. In short, there were no separation of layers, and the code would only work from the scenario in which it was first designed at, and now there were more scenarios (like requests from an API or from other devices) So I had to redesign. I found myself moving all the DB code to objects which acts like Business to DB objects, and I've put all the business logic in an Operator kind of a class, which I've implemented like this: First, I created an object which will hold all the information needed for the operation let's call it InformationObject. Then I created an OperatorObject which will take the InformationObject as a parameter and act on it. The OperatorObject should activate different objects and validate or check for existence or any scenario in which the business logic is compromised and then make the operation according to the information on the InformationObject. So my question is - Is this kind of implementation correct? PS, this Operator only works on a single Business-wise Operation.

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• Recommended design pattern for object with optional and modifiable attributtes? [on hold]

  - by Ikuzen

  I've been using the Builder pattern to create objects with a large number of attributes, where most of them are optional. But up until now, I've defined them as final, as recommended by Joshua Block and other authors, and haven't needed to change their values. I am wondering what should I do though if I need a class with a substantial number of optional but non-final (mutable) attributes? My Builder pattern code looks like this: public class Example { //All possible parameters (optional or not) private final int param1; private final int param2; //Builder class public static class Builder { private final int param1; //Required parameters private int param2 = 0; //Optional parameters - initialized to default //Builder constructor public Builder (int param1) { this.param1 = param1; } //Setter-like methods for optional parameters public Builder param2(int value) { param2 = value; return this; } //build() method public Example build() { return new Example(this); } } //Private constructor private Example(Builder builder) { param1 = builder.param1; param2 = builder.param2; } } Can I just remove the final keyword from the declaration to be able to access the attributes externally (through normal setters, for example)? Or is there a creational pattern that allows optional but non-final attributes that would be better suited in this case?

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• Why can't we capture the design of software more effectively?

  - by Ira Baxter

  As engineers, we all "design" artifacts (buildings, programs, circuits, molecules...). That's an activity (design-the-verb) that produces some kind of result (design-the-noun). I think we all agree that design-the-noun is a different entity than the artifact itself. A key activity in the software business (indeed, in any business where the resulting product artifact needs to be enhanced) is to understand the "design (the-noun)". Yet we seem, as a community, to be pretty much complete failures at recording it, as evidenced by the amount of effort people put into rediscovering facts about their code base. Ask somebody to show you the design of their code and see what you get. I think of a design for software as having: An explicit specification for what the software is supposed to do and how well it does it An explicit version of the code (this part is easy, everybody has it) An explanation for how each part of the code serves to achieve the specification A rationale as to why the code is the way it is (e.g., why a particualr choice rather than another) What is NOT a design is a particular perspective on the code. For example [not to pick specifically on] UML diagrams are not designs. Rather, they are properties you can derive from the code, or arguably, properties you wish you could derive from the code. But as a general rule, you can't derive the code from UML. Why is it that after 50+ years of building software, why don't we have regular ways to express this? My personal opinion is that we don't have good ways to express this. Even if we do, most of the community seems so focused on getting "code" that design-the-noun gets lost anyway. (IMHO, until design becomes the purpose of engineering, with the artifact extracted from the design, we're not going to get around this). What have you seen as means for recording designs (in the sense I have described it)? Explicit references to papers would be good. Why do you think specific and general means have not been succesful? How can we change this?

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• (Database Design - products attributes): What is better option for product attribute database design

  - by meyosef

  Hi, I new in database design. What is better option for product attribute database design for cms?(Please suggest other options also). option 1: 1 table products{ id product_name color price attribute_name1 attribute_value1 attribute_name2 attribute_value2 attribute_name3 attribute_value3 } option 2: 3 tables products{ id product_name color price } attribute{ id name value } products_attribute{ products_id attribute_id } Thanks, Yosef

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• What are the software design essentials? [closed]

  - by Craig Schwarze

  I've decided to create a 1 page "cheat sheet" of essential software design principles for my programmers. It doesn't explain the principles in any great depth, but is simply there as a reference and a reminder. Here's what I've come up with - I would welcome your comments. What have I left out? What have I explained poorly? What is there that shouldn't be? Basic Design Principles The Principle of Least Surprise – your solution should be obvious, predictable and consistent. Keep It Simple Stupid (KISS) - the simplest solution is usually the best one. You Ain’t Gonna Need It (YAGNI) - create a solution for the current problem rather than what might happen in the future. Don’t Repeat Yourself (DRY) - rigorously remove duplication from your design and code. Advanced Design Principles Program to an interface, not an implementation – Don’t declare variables to be of a particular concrete class. Rather, declare them to an interface, and instantiate them using a creational pattern. Favour composition over inheritance – Don’t overuse inheritance. In most cases, rich behaviour is best added by instantiating objects, rather than inheriting from classes. Strive for loosely coupled designs – Minimise the interdependencies between objects. They should be able to interact with minimal knowledge of each other via small, tightly defined interfaces. Principle of Least Knowledge – Also called the “Law of Demeter”, and is colloquially summarised as “Only talk to your friends”. Specifically, a method in an object should only invoke methods on the object itself, objects passed as a parameter to the method, any object the method creates, any components of the object. SOLID Design Principles Single Responsibility Principle – Each class should have one well defined purpose, and only one reason to change. This reduces the fragility of your code, and makes it much more maintainable. Open/Close Principle – A class should be open to extension, but closed to modification. In practice, this means extracting the code that is most likely to change to another class, and then injecting it as required via an appropriate pattern. Liskov Substitution Principle – Subtypes must be substitutable for their base types. Essentially, get your inheritance right. In the classic example, type square should not inherit from type rectangle, as they have different properties (you can independently set the sides of a rectangle). Instead, both should inherit from type shape. Interface Segregation Principle – Clients should not be forced to depend upon methods they do not use. Don’t have fat interfaces, rather split them up into smaller, behaviour centric interfaces. Dependency Inversion Principle – There are two parts to this principle: High-level modules should not depend on low-level modules. Both should depend on abstractions. Abstractions should not depend on details. Details should depend on abstractions. In modern development, this is often handled by an IoC (Inversion of Control) container.

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• Are factors such as Intellisense support and strong typing enough to justify the use of an 'Anaemic Domain Model'?

  - by David Osborne

  It's easy to accept that objects should be used in all layers except a layer nominated as a data layer. However, it's just as easy to end-up with an 'anaemic domain model' that is just an object representation of data with no real functionality ( http://martinfowler.com/bliki/AnemicDomainModel.html ). However, using objects in this fashion brings the benefit of factors such as Intellisense support, strong typing, readability, discoverability, etc. Are these factors strong arguments for an otherwise, anaemic domain model?

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• Design patterns for Agent / Actor based concurrent design.

  - by nso1

  Recently i have been getting into alternative languages that support an actor/agent/shared nothing architecture - ie. scala, clojure etc (clojure also supports shared state). So far most of the documentation that I have read focus around the intro level. What I am looking for is more advanced documentation along the gang of four but instead shared nothing based. Why ? It helps to grok the change in design thinking. Simple examples are easy, but in a real world java application (single threaded) you can have object graphs with 1000's of members with complex relationships. But with agent based concurrency development it introduces a whole new set of ideas to comprehend when designing large systems. ie. Agent granularity - how much state should one agent manage - implications on performance etc or are their good patterns for mapping shared state object graphs to agent based system. tips on mapping domain models to design. Discussions not on the technology but more on how to BEST use the technology in design (real world "complex" examples would be great).

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• N-Tiered application design tool

  - by Ben V

  I'm beginning the design of a medium-sized web application. I usually like to design from the top down, i.e., start at the highest level and design my way down. I am planning to have the following layers: Presentation (PHP/Ajax) Business Logic Data Access Database Now I'd like to start sketching out the major objects in each layer and the interaction between layers. Is there a tool more specific to this purpose than just using a graphics/diagramming tool like Visio?

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• Good design of mapping Java Domain objects to Tables (using Hibernate)

  - by M. McKenzie

  Hey guys, I have a question that is more in the realm of design, than implementation. I'm also happy for anyone to point out resources for the answer and I'll gladly, research for myself. Highly simplified Java and SQL: Say I have a business domain POJO called 'Picture' with three attributes. class Picture int idPicture String fileName long size Say I have another business domain POJO called "Item" with 3 attributes Class Item int idItem String itemName ArrayList itemPictures These would be a normal simple relationship. You could say that 'Picture' object, will never exist outside an 'Item' object. Assume a picture belongs only to a specific item, but that an item can have multiple pictures Now - using good database design (3rd Normal Form), we know that we should put items and pictures in their own tables. Here is what I assume would be correct. table Item int idItem (primary key) String itemName table Picture int idPicture (primary key) varchar(45) fileName long size int idItem (foreign key) Here is my question: If you are making Hibernate mapping files for these objects. In the data design, your Picture table needs a column to refer to the Item, so that a foreign key relation can be maintained. However,in your business domain objects - your Picture does not hold a reference/attribute to the idItem - and does not need to know it. A java Picture instance is always instantiated inside an Item instance. If you want to know the Item that the Picture belongs to you are already in the correct scope. Call myItem.getIdItem() and myItem.getItemPictures(),and you have the two pieces of information you need. I know that Hibernate tools have a generator that can auto make your POJO's from looking at your database. My problem stems from the fact that I planned out the data design for this experiment/project first. Then when I went to make the domain java objects, I realized that good design dictated that the objects hold other objects in a nested way. This is obviously different from the way that a database schema is - where all objects(tables) are flat and hold no other complex types within them. What is a good way to reconcile this? Would you: (A) Make the hibernate mapping files so that Picture.hbm.xml has a mapping to the POJO parent's idItem Field (if it's even possible) (B) Add an int attribute in the Picture class to refer to the idItem and set it at instantiation, thus simplifying the hbm.xml mapping file by having all table fields as local attributes in the class (C) Fix the database design because it is wrong, dork. I'd truly appreciate any feedback

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• General Overview of Design Pattern Types

  Typically most software engineering design patterns fall into one of three categories in regards to types. Three types of software design patterns include: Creational Type Patterns Structural Type Patterns Behavioral Type Patterns The Creational Pattern type is geared toward defining the preferred methods for creating new instances of objects. An example of this type is the Singleton Pattern. The Singleton Pattern can be used if an application only needs one instance of a class. In addition, this singular instance also needs to be accessible across an application. The benefit of the Singleton Pattern is that you control both instantiation and access using this pattern. The Structural Pattern type is a way to describe the hierarchy of objects and classes so that they can be consolidated into a larger structure. An example of this type is the Façade Pattern.  The Façade Pattern is used to define a base interface so that all other interfaces inherit from the parent interface. This can be used to simplify a number of similar object interactions into one single standard interface. The Behavioral Pattern Type deals with communication between objects. An example of this type is the State Design Pattern. The State Design Pattern enables objects to alter functionality and processing based on the internal state of the object at a given time.

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• CIC 2010 - Ghost Stories and Model Based Design

  - by warren.baird

  I was lucky enough to attend the collaboration and interoperability congress recently. The location was very beautiful and interesting, it was held in the mountains about two hours outside Denver, at the Stanley hotel, famous both for inspiring Steven King's novel "The Shining" and for attracting a lot of attention from the "Ghost Hunters" TV show. My visit was prosaic - I didn't get to experience the ghosts the locals promised - but interesting, with some very informative sessions. I noticed one main theme - a lot of people were talking about Model Based Design (MBD), which is moving design and manufacturing away from 2d drawings and towards 3d models. 2d has some pretty deep roots in industrial manufacturing and there have been a lot of challenges encountered in making the leap to 3d. One of the challenges discussed in several sessions was how to get model information out to the non-engineers in the company, which is a topic near and dear to my heart. In the 2D space, people without access to CAD software (for example, people assembling a product on the shop floor) can be given printouts of the design - it's not particularly efficient, and it definitely isn't very green, but it tends to work. There's no direct equivalent in the 3D space. One of the ways that AutoVue is used in industrial manufacturing is to provide non-CAD users with an easy to use, interactive 3D view of their products - in some cases it's directly used by people on the shop floor, but in cases where paper is really ingrained in the process, AutoVue can be used by a technical publications person to create illustrative 2D views that can be printed that show all of the details necessary to complete the work. Are you making the move to model based design? Is AutoVue helping you with your challenges? Let us know in the comments below.

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• Design for XML mapping scenarios between two different systems [on hold]

  - by deepak_prn

  Mapping XML fields between two systems is a mundane routine in integration scenarios. I am trying to make the design documents look better and provide clear understanding to the developers especially when we do not use XSLT or any other IDE such as jDeveloper or eclipse plugins. I want it to be a high level design but at the same time talk in developer's language. So that there is no requirements that slip under the crack. For example, one of the scenarios goes: the store cashier sells an item, the transaction data is sent to Data management system. Now, I am writing a functional design for the scenario which deals with mapping XML fields between our system and the data management system. Question : I was wondering if some one had to deal with mapping XML fields between two systems? (without XSLT being involved) and if you used a table to represent the fields mapping (example is below) or any other visualization tool which does not break the bank ? I am trying to find out if there is a better way to represent XML mapping in your design documents. The widely accepted and used method seems to be using a simple table such as in the picture to illustrate the mapping. I am wondering if there are alternate ways/ tools to represent such as in Altova:

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• How to design good & continuous tiles

  - by Mikalichov

  I have trouble designing tiles so that when assembled, they don't look like tiles, but look like an homogeneous thing. For example on the image below: even though the main part of the grass is only one tile, you don't "see" the grid; you know where it is if you look a bit carefully, but it is not obvious. Whereas when I design tiles, you can only see "oh, jeez, 64 times the same tile". A bit like on that image: (taken from a gamedev.stackexchange question, sorry; no critic about the game, but it proves my point, and actually has better tile design that what I manage) I think the main problem is that I design them so they are independent, there is no junction between two tiles if put closed to each other. I think having the tiles more "continuous" would have a smoother effect, but can't manage to do it, it seems overly complex to me. I think it is probably simpler than I think once you know how to do it, but couldn't find a tutorial on that specific point. Is there a known method to design continuous / homogeneous tiles? (my terminology might be totally wrong, don't hesitate to correct me)

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• How can I design good continuous (seamless) tiles?

  - by Mikalichov

  I have trouble designing tiles so that when assembled, they don't look like tiles, but look like a homogeneous thing. For example, see the image below: Even though the main part of the grass is only one tile, you don't "see" the grid; you know where it is if you look a bit carefully, but it is not obvious. Whereas when I design tiles, you can only see "oh, jeez, 64 times the same tile," like in this image: (I took this from another GDSE question, sorry; not be critical of the game, but it proves my point. And actually has better tile design that what I manage, anyway.) I think the main problem is that I design them so they are independent, there is no junction between two tiles if put closed to each other. I think having the tiles more "continuous" would have a smoother effect, but can't manage to do it, it seems overly complex to me. I think it is probably simpler than I think once you know how to do it, but couldn't find a tutorial on that specific point. Is there a known method to design continuous / homogeneous tiles? (My terminology might be totally wrong, don't hesitate to correct me.)

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• Learning good OOP design & unlearning some bad habits

  - by Nick

  I have been mostly a C programmer so far in my career with knowledge of C++. I rely on C++ mostly for the convenience STL provides and I hardly ever focus on good design practices. As I have started to look for a new job position, this bad habit of mine has come back to haunt me. During the interviews, I have been asked to design a problem (like chess, or some other scenario) using OOP and I doing really badly at that (I came to know this through feedback from one interview). I tried to google stuff and came up with so many opinions and related books that I don't know where to begin. I need a good through introduction to OOP design with which I can learn practical design, not just theory. Can you point me to any book which meets my requirements ? I prefer C++, but any other language is fine as long as I can pick-up good practices. Also, I know that books can only go so far. I would also appreciate any good practice project ideas that helped you learn and improve your OOP concepts. Thanks.

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• Level Design V.S. Modeler

  - by Ecurbed

  From what I understand being a level designer and a character/environment/object/etc Modeler are two different jobs, yet sometimes it feels like a Modeler can also do the job of the level designer. I know this also depends on the scale of the game. For small games maybe they are one and the same, but for bigger games they become two different jobs. I understand a background in some modeling could not hurt when it comes to level design, but the question I have is: Do jobs prefer people who can model for level designing? This way they can kill two birds with one stone and have someone to create the assets and design the level. What is your opinion of the training? Does level design contain skill sets that make them completely different from what a modeler can do, or is this an easy transition for a modeler to become a level designer? Can you be a bad level designer but a good modeler and vice versa?

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• How to design network protocols

  - by dandroid

  As a programmer, you work on your software design skills. You learn about things such as modularity and reusability and how you can achieve them in code. There's plenty of literature on the subject and engineers talk about it all the time. What about if you want to design network protocols? How do you judge that protocol X is badly designed while Y is well designed? (eg. in programming you are often pointed out to a well-written piece of code in order to learn from it - what is the equivalent for network protocols?) For example, suppose I want to design a P2P protocol similar to BitTorrent or I want to make a better version of the Socks protocol. How would I go about doing a good job on this? Thanks!

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• Green Website Design

  - by Christofian

  This is kindove a strange question, but... There was a site called Blackle ( http://www.blackle.com/) which "claimed" to save energy by using a black background (it doesn't: see here: http://skeptics.stackexchange.com/questions/4373/how-much-energy-does-displaying-a-webpage-with-a-black-background-actually-save). However, blackle and it's idea of "green website design" interested me, and I was wondering if there are any ways to design an energy saving website that actually save energy. If anyone knows of any, please post them here. If nobody has any, then I guess there isn't a way to save energy through website design...

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• Advice about a website design [closed]

  - by Dimitri

  I am web developer newbie. It doesn't mean that I don't know html/css/javascript but I am not good for web design. I am making a website for friend about a barber shop but I am not totally happy of my work due to lack of design. I would like to have some advice about the website and how can I improve the design? The website is in french because i am french. Here is the website : http://afrostyle92.fr/.

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