How should UI layer pass user input to BL layer?

I’m building an n-tier application, I have UI, BL, DAL & Entities (built from POCO) projects. (All projects have a reference to the Entities).

Is it a good idea to design an architecture thinking that the User Interface classes can be replaced by a command line interface?

In Code Complete page 25, it’s said that it’s a good idea to be able to easily replace the regular user interface classes by a command line one.

The limit of Int32 for Identity Column

This is just a consideration for a site am creating and for other big sites out there.

When designing an enterprise API, what level is appropriate for separating libraries?

Assume we are developing a REST system for an enterprise company to expose the companies resources in a Java based application. Ultimately you have one web application, and domain libraries. My question is to where components and services should live in these domain libraries and what should exist in the application itself.

Inventory management system design problem

What are the conventions for item batch identifiers in inventory management systems?

Should I prefer instance methods over class methods in Ruby?

I’m working on a rails application, and I’ve been pulling functionality out of my rails code and into pure ruby classes in lib/. I’ve found myself often writing classes like this:

How to unit test a function that is refactored to strategy pattern?

If I have a function in my code that goes like:

Is it possible to migrate struts/spring based application to GWT?

I am using the combination of spring, spring-security, struts and iBatis in my application. Now I am looking to migrate the struts UI to GWT.

When should code favour optimization over readability and ease-of-use?

I am in the process of designing a small library, where one of my design goals is that the API should be as close to the domain language as possible. While working on the design, I’ve noticed that there are some cases in the code where a more intuitive, readable attribute/method call requires some functionally unnecessary encapsulation. Since the final product will not necessarily require high performance, I am unconcerned about making the decision to favour ease-of-use in my current project over the most efficient implementation of the code in question.

Design documents as part of Agile

At my workplace, we face a challenge in that “agile” too often has meant “vague requirements, bad acceptance criteria, good luck!” We’re trying to address that, as a general improvement effort.