Implementation is the realization of an application, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy.

In computer science, an implementation is a realization of a technical specification or algorithm as a program, software component, or other computer system through computer programming and deployment. Many implementations may exist for a given specification or standard. For example, web browsers contain implementations of World Wide Web Consortium-recommended specifications, and software development tools contain implementations of programming languages.

A special case occurs in object-oriented programming, when a concrete class implements an interface; in this case the concrete class is an implementation of the interface and it includes methods which are implementations of those methods specified by the interface.

Information technology

In the information technology during industry, implementation refers to post-sales process of guiding a client from purchase to use of the software or hardware that was purchased. This includes requirements analysis, scope analysis, customizations, systems integrations, user policies, user training and delivery. These steps are often overseen by a project manager using project management methodologies. Software Implementations involve several professionals that are relatively new to the knowledge based economy such as business analysts, technical analysts, solutions architects, and project managers.

To implement a system successfully, many inter-related tasks need to be carried out in an appropriate sequence. Utilising a well-proven implementation methodology and enlisting professional advice can help but often it is the number of tasks, poor planning and inadequate resourcing that causes problems with an implementation project, rather than any of the tasks being particularly difficult. Similarly with the cultural issues it is often the lack of adequate consultation and two-way communication that inhibits achievement of the desired results.

Political science
In political science, implementation refers to the carrying out of public policy. Legislatures pass laws that are then carried out by public servants working in bureaucratic agencies. This process consists of rule-making, rule-administration and rule-adjudication. Factors impacting implementation include the legislative intent, the administrative capacity of the implementing bureaucracy, interest group activity and opposition, and presidential or executive support.

In international relations, implementation refers to a stage of international treaty-making. It represents the stage when international provisions are enacted domestically through legislation and regulation. The implementation stage is different from the ratification of an international treaty.

Social and health sciences

Implementation is defined as a specified set ofactivities designed to put into practice an activity or program of known dimensions. According to this definition, implementation processes are purposeful and are described in sufficient detail such that independent observers can detect the presence and strength of the “specific set of activities” related to implementation. In addition, the activity or program being implemented is described in sufficient detail so that independent observers can detect its presence and strength.”[1]

Water and natural resources

In water and natural resources, implementation refers to the actualization of best management practices with the ultimate goals of conserving natural resources and improving the quality of water bodies.