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An overview of open APIs and their benefits (part 1)
By Thadpong Pongthawornkamol, Senior Visionary Architect - KBTG

An API (Application Programming Interface) specifies a way for a computer process (e.g., desktop program, mobile application, device firmware) to communicate and use service provided by another computer process, thereby allowing multiple computing entities to interact with each other without human intervention. API is not a new concept, but has existed since the inception of computer programming. However, traditional APIs are in the form of closed APIs. In closed APIs (a.k.a. private APIs), an interaction between computing entities usually takes place within the same organization for the purpose of modularity, code reusability, and system manageability. On the other hand, a new form of APIs called open APIs have recently started to gain popularity and widespread adoption. In open APIs (a.k.a. public APIs), an interaction between processes usually happens across organization boundary for the purpose of outsourcing, interoperability, and economy of scale. For example, a running / jogging application may need to track and display a user's location on the map so that the user knows where she is. Instead of building its own map database from scratch, the running application team can use existing mapping service APIs (e.g., Google Maps, Microsoft Bing Maps) to do all the mapping works while focusing its effort on developing core app functionalities such as step counting and calorie estimation.

Over the past few years, there has been a significant increase in the number of open API providers and open API usage level. According, there are currently over 17,000 open APIs available across various categories (e.g., search, social, finance, content)[1]. In this article and more forthcoming articles, we give an overview of open APIs in some selected categories as well as describe a few notable examples in such categories in order to demonstrate the benefits of open APIs. In this article, we will start with one of the most prominent open API categories: E-commerce.

Online shopping is one of the most common reasons people use Internet for. However, instead of human users searching or browsing the products on page manually, a computer program can use Amazon's product advertising API[2] to programmatically access's product selection and its various information (e.g., product descriptions and customer reviews) as well as add products to a user's cart.

While Amazon provides buy-side functionalities through its APIs,'s Buy and Sell APIs[3] provides both buy-side and sell-side services in order to complete the whole e-commerce cycle. Product buyers (or their application agents) can use Ebay Buy APIs to obtain / search product information, receive product recommendations, make the purchase, and track shipping orders. On the other side, product sellers (or their application agents) can use Ebay Sell APIs to create product catalogs, manage inventory, advertise products, fulfill orders, as well as handle post-sale customer relationship management.

In addition to generic e-commerce websites such as Amazon and Ebay, many specialty e-commerce businesses also provide their services in the form of open APIs as well., a leading online marketplace for handmade products, provides an API set that encapsulates both buy-side and sell-side functionalities such as Shop, Listing, Payment, Cart, and Feedback[4]. iTunes, a popular online store for mobile apps and music, provides iTunes Search API to search its products' information based on keywords (e.g., title, authors, artists, regions)[5]. 

Through open APIs, many e-commerce businesses do not limit their services to be used by just human users, but instead allow other applications to be built on top of their services in order to add more values and variety into the ecosystem. For example, a social network application can assess its user profile and preferences and then use e-commerce search APIs to recommend products to the user. A small business management application can use sell side APIs to list products on various marketplaces so that a shop owner does not need to post her products on each marketplace manually. The possibility is limitless - there are many more ideas and business opportunities to be discovered.

In the next article, we will visit a few more open API categories as well as their representative examples. 

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