Application Programming Interface API stands for Application Programming Interface
Programming Instructions An application-programming interface (API) is a set of programming instructions and standards for accessing a Web-based software application or Web tool .
Released publicly A software company releases its API to the public so that other software developers can design products that are powered by its service.
Software interface An API is a software-to-software interface, not a user interface. With APIs, applications talk to each other without any user knowledge or intervention.
Seamless Integration The user never notices when software functions are handed from one application to another. This type of integration is called seamless.
Resembles SaaS An API resembles Software as a Service (SaaS), since software developers don't have to start from scratch every time they write a program. Instead of building one core application that tries to do everything -- e-mail, billing, tracking, etcetera -- the same application can contract out certain responsibilities to remote software that does it better.
Example When you buy movie tickets online and enter your credit card information, the movie ticket Web site uses an API to send your credit card information to a remote application that verifies whether your information is correct. Once payment is confirmed, the remote application sends a response back to the movie ticket Web site saying it's OK to issue the tickets.
Series of Calls An API allows a software application to communicate with a remote application over the Internet through a series of calls
Web Services With APIs, the calls back and forth between applications are managed through something called Web services .
XML Web services are a collection of technological standards and protocols, including XML (Extensible Markup Language) , the programming language by which applications communicate over the Internet.
XML Messages The API itself is a chunk of software code written as a series of XML messages . Each XML message corresponds to a different function of the remote service.
SDK Companies who release their API often do so as part of a larger software development kit (SDK) that includes the API, programming tools and other instructional documents to make the developer's job easier.
Invisible to user APIs and Web services are completely invisible to Web site surfers and software users. Their job is to run silently in the background, providing a way for applications to work with each other to get the user the information or functionality he needs.
Acronymns Standards, protocols and programming languages that make Web services work: SOAP (Simple Object Access Protocol) UDDI (Universal Description, Discovery and Integration) WSDL (Web Services Description Language)
SOAP SOAP (Simple Object Access Protocol) : responsible for encoding XML messages so they can be received and understood by any operating system over any type of network protocol.
UDDI UDDI (Universal Description, Discovery and Integration) : Described as a "yellow pages for the Internet," UDDI is an XML-based directory that allows businesses to list themselves, find each other and collaborate using Web services.
WSDL WSDL (Web Services Description Language) : WDSL is the SOAP of the UDDI (enough acronyms for you?). Basically, WDSL is the XML-based language that businesses use to describe their services in the UDDI.
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