Layer (or abstraction level, or a layer of abstraction) is a way of hiding the implementation details of a particular set of functionality.

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Refactoring to avoid circular references

I'm working on an ASP.NET MVC solution that has two projects, WebUI and DAL. WebUI references DAL. DAL has the repository and context, while WebUI contains Authentication and Authorization classes. ...
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87 views

Where should business logic go in a layered architecture?

First of all, i'm not talking about validation in the sense of the nullability or length of a field like in this and this questions where we can use isValid() methods in business classes or an ...
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2answers
88 views

Abstracton layer to control services access to denormalized db entity

Our db is optimized for minimum join count (partially denormalized). E.g. our User entity contains account data (nickname, facebook id, etc), user numerical statistics (total games played, total wins, ...
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20 views

Abstracting AutoLayout sensibly - why is this so conceptually tough and where should I begin?

Below are some babbling, probably incoherent thoughts, but I am so stuck on this problem and I feel like an elegant solution is possible. Though it is indisputably awesome, and makes programatic view ...
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1answer
288 views

OOP - How to refactor a “pyramid architecture”

Unbeknownst to me while I was building it, I built a "pyramid" architecture. I did not realize this until I laid it out in my new Visual Studio 2013 Layer Diagrammer. Each layer depends on the layer ...
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2answers
102 views

Do web applications use HTTP as a transport layer, or do they count as an integral part of the HTTP server?

Given an HTTP server (e.g. Apache, IIS) and a web application (user code running in the server using PHP, ASP.NET and the likes), which of those can decide which HTTP status code to return for any ...
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3answers
748 views

DDD, modularizing the application and domain layers without breaking the DIP

Quoting DDD theory: The application layer is thin in terms of domain logic - it merely coordinates the domain layer objects to perform the actual work. When it comes to modularization, and ...
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4answers
224 views

N-Layer architecture

I am attempting to structure my solution projects in such a manner as to improve testing, reuseability, separation of concerns and all that good stuff. Whilst I understand these concepts in theory, I ...
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4answers
422 views

Domain Model, validation, and pushing errors to the model

Looking into DDD and something I noticed is that business logic should be in the model, otherwise you just have property bags. That said how do you handle pieces of validation that require a trip to ...
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2answers
107 views

What layers reference each other in a multi layer design? [duplicate]

I'm creating a project and I'm having difficulty and contrasting opinions on how to do things when it comes down to separating layers. I'm not fully sure what layers should reference each other. I ...
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2answers
177 views

Where should the “not empty field” validation code be written on a 3-layer application?

When working with the 3-layer model, where should the validation code be placed? for: not empty fields, unchecked options, null values, wrong-written dates, etc. To keep total isolation between a ...
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3answers
719 views

Business Logic vs Presentation/View Logic

I often question myself of where to put the logic that organize the data to a view that is not necessarily a business logic in a 3-layered architecture (DAO, Business, View). I'll put an example to ...
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1answer
176 views

Confused about layered application development

So, for the first big project that I'm getting paid for, I decided I'd do things right. To that end, I've created several projects in my Solution. Some of these projects are generic and handle common ...
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2answers
179 views

Can a layer consist of multiple projects / dlls?

I am working on the architecture for a new web application and I am pretty much a complete newbie when it comes to architecture. Working my way through .NET Application Architecture Guide, 2nd Edition ...
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1answer
97 views

How to handle errors best addressed in a higher abstraction layer and dependent on state inferred in current layer?

I have a use-case that can be repaired, but the logic for repairing it is best done in a higher level of abstraction. Just throwing exception/failure is ugly because it's hard to pass back up through ...
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1answer
176 views

Where do utility libraries fit in a layered architecture?

Consider this mock-up of a software stack designed with layered architecture in mind : Every application layer is decoupled through API calls, but a memory handling library is used throughout. All ...
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1answer
249 views

Lazy Loading, DAL and BLL abstraction

I'm asking myself a question to code the right way on a new fresh project. I have a designed database and I mapped tables to equivalent POCO classes using Entity Framework 6 Code First. Then, I ...
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2answers
276 views

What are the advantages of strictly maintaining separate data | algorithm | interface layers?

I always separate the user interface from other functionality in my programs - its the way I have been taught, and it has obvious advantages since you can change the interface but keep the same ...
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2answers
167 views

Best practice for security checks, in surface or deep layer? [closed]

Let's take a server-side WebServices app, we need to make sure that all function applies every security rules, and keep the code clean. In such a case, I usually prefer to place my security checks on ...
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1answer
107 views

Data Access Layer for application

I am working on a retail application where currently I'm using raw SQL like insert into some_table values (Textbox1.Text, Textbox2.Text, ...) and update some_table set some_column = value for ...
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1answer
287 views

Where does non-MVVM code belong in an MVVM app?

By non-MVVM code, I mean things like highly generalized components, like one with common extension methods for CLR types, and other 'homeless' helper classes etc? I have a Core project that most ...
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3answers
1k views

What is an “abstraction layer”?

I need a very simple explanation because I'm not a professional programmer. I found the terminology "abstraction layer" reading the documentation of mysqli extension where is described the difference ...
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3answers
766 views

DAL vs BLL functions' return types

Here is how I see the main differences between the DAL and the BLL: The DAL directly query the database. The DAL doesn't create new information. It may execute complex sql requests, joining several ...
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1answer
238 views

How to avoid dragging arguments from function to function

When I do my code layout, I like to start with a rather high level view, and then start to delegate actual computation to class or functions that have a bit more detail. Then in these classes of ...
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11answers
33k views

How accurate is “Business logic should be in a service, not in a model”?

Situation Earlier this evening I gave an answer to a question on StackOverflow. The question: Editing of an existing object should be done in repository layer or in service? For example ...
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2answers
672 views

Is programming in layers real? [duplicate]

I am fairly new in product development and I am trying to work over a product. The problem that I have realized is that people draw diagrams and charts showing different modules and layers. But as I ...
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1answer
129 views

Layer style applied, but intuition is different

Currently, I'm developing an architecture for a system of the following kind: There are a couple of existing applications (front end) with which one can define UML profiles capturing some specific ...
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3answers
452 views

How do I create a simple yet complex business layer?

I'm working with a fairly complex web application. It's split up into the following layers: Presentation - HTML Service layer - A REST and SOAP API communicating with the business layer Business ...
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68 views

Layer Encapsulation without Model Overload?

I'm starting a new project, so it's time to re-evaluate how I do things. In the recent past I have created a 3 layer/tier project (UI, Domain, Data) with each tier with it's own separate model. The ...
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3answers
125 views

Efficiently “moving” data upward through a communication stack

I have implemented an application protocol stack that moves an incoming stream of data upward through several layers, as follows: copies a TCP segment from an OS buffer to my_buffer. after ...
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3answers
699 views

Which layer does async code belong?

I am developing an application that consumes data from an external service. The application is being implemented following a typical layered architecture with UI, Presentation, Domain and Data ...
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1answer
740 views

Trying to understand 3 layer programming [closed]

I am confused to understand the structure of a 3 layer programm. Where is good place for exceptions, entity and etc.? If I use MVC, in my UI model, how to transfer entity class to model class and ...
61
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13answers
6k views

Why is it a good idea for “lower” application layers not to be aware of “higher” ones?

In a typical (well-designed) MVC web app, the database is not aware of the model code, the model code is not aware of the controller code, and the controller code is not aware of the view code. (I ...
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1answer
306 views

Why doesn't layered architecture translate easily to tiered architecture?

Basically, I'm trying to understand why layered and tiered are that different, and why they don't translate easily to each other. I understand that layered could be 3 separate class files for UI, BL ...
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248 views

Large teams with layered application

I work in a fairly large team (~15 developers) which is currently discussing our working methodology. The software we work on is quite feature-rich and expanding rapidly in terms of scope so the ...
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2answers
3k views

How do the Application and Database Interface Layers interact at their boundary?

I was watching one of Uncle Bob's videos and he brought up the Database Interface Layer. He had this diagram showing it: These arrows show that the DB Interface Layer is aware of and calls the ...
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3answers
798 views

Good practices to implement mappers in a multi-tier application

When you are working with a multi-tier application very often you run into task of converting objects in one layer to objects in another layer. This could be converting database objects into domain ...
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3answers
2k views

Presentation VS Application layer in DDD

I have trouble drawing a clear line between Presentation and Application layer in Domain Driven Design. Where should Controllers, Views, Layouts, Javascript and CSS files go? Is it in the ...
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1answer
177 views

When do domain concepts become application constructs?

I recently posted a question regarding recovering a DDD architecture that became an anemic domain model into a multitier architecture and this question is a follow-on of sorts. My question is when ...
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5answers
5k views

Do stored procedures violate three-tier separation?

Some colleagues of mine have told me that having business logic in stored procedures in the database violates the three-tier separation, since the database belongs to the data layer whereas stored ...
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3answers
4k views

PHP - Data Access Layer

I am currently reviewing a code base and noticed that a majority of the calls (along with DB connections) are just buried inside the PHP scripts. I would have assumed that like other languages they ...
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4answers
286 views

Processing a stream. Must layers be violated?

Theoretical situation: One trillion foobars are stored in a text file (no fancy databases). Each foobar must have some business logic executed on it. A set of 1 trillion will not fit in memory so the ...
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6answers
3k views

When to use the 3 layers model?

I was recently exposed to the three layer model (DAL,BL,UI). Someone told me I should ALWAYS work with this model. I have a medium project that I'm starting and I have doubts whether I should build ...
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2answers
9k views

Does it make sense to use ORM in Android development?

Does it make sense to use an ORM in Android development or is the framework optimized for a tighter coupling between the UI and the DB layer? Background: I've just started with Android development, ...
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3answers
691 views

Event driven design and separation of core/UI logic

I am new to event driven development, and I feel lost when I try to implement events that should pass the core/UI boundary. In my program I have the following (example in c#): UI.RuleForm ...
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1answer
932 views

Effective programming of data layer management/access

Short Version: What is the term/concept which describes the efficient design of programming the data layer for efficient data access and what are some sources/books/articles/website which discuss this ...
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3answers
3k views

Validation and authorization in layered architecture

I know you are thinking (or maybe yelling), "not another question asking where validation belongs in a layered architecture?!?" Well, yes, but hopefully this will be a little bit of a different take ...
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3answers
267 views

What are the pros and cons of implementing this requirement in different layers?

I have a CRUD app for <DomainObject>s. They are persisted in a database. There is a new requirement: keep track of the <DomainObject>s that have been created since the app was opened, ...
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4answers
1k views

n-layers architecture design, really worth the effort?

I was building an application in .Net for almost a year (almost alone), I took the decision to build it with a 3-layer design. Recently when finished the project, I analyzed if the effort of creating ...
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942 views

Entity Framework and “ViewModel”

Earlier I asked a question about "Entity Framework and layer seperation" and found out that some people use a ViewModel to show their data in the UI. For example if we got a "Person" table and an ...