Ralph E. Johnson. Frameworks = (components + patterns). Commun. ACM, 40(10):39--42, 1997. Like software libraries, software frameworks aid the software developer by containing source code that solves problems for a given domain and provides a simple API. However, while a code library acts like a servant to other programs, software frameworks reverse the master/servant relationship. This reversal, called inversion of control, expresses the essence of software frameworks.^[1]

Motivations

The designers of software frameworks aim to facilitate software development by allowing designers and programmers to spend more time on meeting software requirements rather than dealing with the more standard low-level details of providing a working system. For example, a team using Apache Struts to develop a banking web site can focus on the operations of account withdrawals rather than on how to control navigation between webpages in a bug-free manner. However, developers commonly complain that using frameworks adds to "code bloat", and that due to competing and complementary frameworks, one trades time spent on rote programming and design for time spent on learning frameworks.

Having a good framework in place allows developers to spend more time concentrating on the business-specific problem at hand rather than on the "plumbing" code behind it. Also a framework will limit choices during development, so it increases productivity, especially in large and complex systems.

Types of software frameworks

A software framework may focus on building graphical editors for different domains like artistic drawing, music composition, and mechanical CAD.^[2][3] Another software framework can help build compilers for different programming languages and target machines.^[4] Yet another might help build financial modeling applications.^[5] or decision support systems^[6] Frameworks exist for multimedia, web applications, and even communicating between different systems.

Architecture

According to Pree,^[7] software frameworks consist of frozen spots and hot spots. On the one hand, frozen spots define the overall architecture of a software system, that is to say its basic components and the relationships between them. These remain unchanged (frozen) in any instantiation of the application framework. On the other hand, hot spots represent those parts where the programmers using the framework add their own code to add the functionality specific to their own project.

Software frameworks define the places in the architecture where application programmers may make adaptations for specific functionality ? the hot spots.

In an object-oriented environment, a framework consists of abstract and concrete classes. Instantiation of such a framework consists of composing and subclassing the existing classes.^[8]

When developing a concrete software system with a software framework, developers utilize the hot spots according to the specific needs and requirements of the system. Software frameworks rely on the Hollywood Principle: "Don't call us, we'll call you."^[9] This means that the user-defined classes (for example, new subclasses), receive messages from the predefined framework classes. Developers usually handle this by implementing superclass abstract methods.

List of general-purpose frameworks

• BFC is a RAD framework for developing database-centric distributed computing applications in a .NET environment.
• CNI (Compiled Native Interface) is a software framework for the GNU GCJ compiler which allows Java code to call and be called by native applications (programs specific to a hardware and operating system platform) and libraries written in C++.
• Component-based Scalable Logical Architecture (CSLA) is a standard way to create robust object oriented programs using business objects, implemented using .NET.
• Java Native Interface (JNI) allows Java code running in the Java virtual machine (VM) to call and be called by native applications (programs specific to a hardware and operating system platform) and libraries written in other languages, such as C, C++ and assembly.
• Leonardi is an open source application framework for GUI applications
• Spring is an open source application framework for the Java platform.
• Symfony is a popular open source application framework for PHP Platform.
• CodeIgniter is a popular open source application framework for PHP Platform.
• Rails is a libre software application framework for the Ruby Platform.

See also

• Application framework
• Class (computer science)
• Don't repeat yourself
• Enterprise Architecture
• Implicit invocation
• Jini | Upnp | Salutation which have been called coordination frameworks.
• Object-oriented programming
• Web application framework

External links

• Annual frameworks conference
• Frameworks vs. Libraries
• RAS metadata repository for creating software assets and software reuse
• XAF application framework from DevExpress
• MX-Frame Business Application Framework

References

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