I originally published this article to ProgrammableWeb.com on December 10, 2012

The purpose of a content API is to make the content available to its audience in the most useful and efficient way possible. To be a useful API, it needs to help the developers make their jobs easier. This could mean a wide range of things, including making it easier to dig into the API, allowing for greater flexibility in the responses, improved performance and efficiency for both the API and its consumer. Below are seven development techniques (all of which are part of the NPR API) that can help content providers improve the usefulness and efficiency of their APIs on both sides of the track. These techniques played a critical role in the success of the API which now delivers over 700 million stories per month to its users (more stats on the NPR API coming soon on our Inside NPR.org blog).

Be Flexible: Support Multiple Output Formats
Making the API as available and accessible as possible is very important in drawing developers to use it. So providing the content in a range of formats will increase the likelihood that the developer can rely on existing libraries and make as few changes to the code as possible.

The NPR API offers eight different output formats in an effort to improve efficiency for the developers. Above is a graph demonstrating the distribution of requests for each of the formats in July of 2009. As you can see, the majority of requests are to our proprietary XML markup (NPRML). That also means that almost 50% of the requests, or about 20M requests per month, use the other seven formats. In offering offering these other non-proprietary XML formats, the API is able to support developers that may have existing applications that pull in content in one of these standardized format, such as MediaRSS or Atom.

To make it even easier for people to use the API, NPR also launched with JavaScript and HTML “widgets”. The other six formats require more sophistication in order to put the content in an application or website. The widgets, however, are pre-designed feeds of NPR content (based on the developer’s selections) that can be easily dropped into a page.

Be Efficient: Handle Partial Response
This concept is now starting to get some more traction, now that Google announced partial response handling for some of their APIs. NPR’s API also makes extensive us of this feature because it really is tremendously valuable to the provider and the consumer of the API. For example, NPR stories contain a wide variety of fields and assets in the API. If the consumer is forced to handle the complete document, even if they only want a few fields, they have to endure all of the latency issues from the API itself as well as the additional processing power needed to handle the undesired fields.

As a result, NPR incorporated a “fields” parameter (the same parameter name used by Google) that can be used in the query string to limit the resulting document to only the fields of interest. This approach creates documents that are smaller and much more efficient. Overwhelmingly, more requests to the NPR API contain the fields parameter than those that do not (in fact, it isn’t even close).

Here are a few examples of how the same query to the NPR API, returning the same stories, delivers different documents based on the fields parameter (you will need to register for your own NPR API key to execute these queries):

http://api.npr.org/query?id=1001&apiKey=your_api_key

http://api.npr.org/query?id=1001&fields=title&apiKey=your_api_key

http://api.npr.org/query?id=1001&fields=title,teaser,text,image,audio&apiKey=your_api_key

An extension of partial response is to allow the developer to specify the number of items they would like in return. Some APIs return a fixed number of results, which can bloat the document just like the extra fields can. The NPR API, to counter this, allows the developer to pass in the number of results desired (with a fixed ceiling for any given request). To dig deeper in the results, we incorporated a “pagination” feature in the API. Here are some examples of how to control the number of stories:

http://api.npr.org/query?id=1001&numResults=5&apiKey=your_api_key

http://api.npr.org/query?id=1001&numResults=5&startNum=6&apiKey=your_api_key

Give Them Control: Allow for Customizable Output Markup (“Remapping Fields”)
As mentioned in the transform section, if the API can easily serve existing applications that expect specific markup, it potentially increases adoption and improves developer efficiency. To extend that functionality, the NPR API offers a function that we call “Remap” which essentially lets the developer modify the name of one or more XML elements or attributes in the output at request time. This is done in the query string and the API transforms the markup accordingly in real-time. Here are a few examples:

In this example, the remap parameter changes the story title to < specialTitle >:

http://api.npr.org/query?id=1001&remap=list.story.title:specialTitle&apiKey=your_api_key

In this example, the remap parameter changes the story title to < specialTitle > and it changes the image caption to < imageCaption >:

http://api.npr.org/query?id=1001&remap=list.story.title:specialTitle,list.story.image.caption:imageCaption&apiKey=your_api_key

In this example, the remap parameter changes the audio element’s id attribute to be named audioId:

http://api.npr.org/query?id=1001&remap=list.story.audio~id:audioId&apiKey=your_api_key

Another benefit to remap (which we have fortunately not had to use) is that it can be used to handle backward compatibility as the API grows and changes. NPR’s philosophy is to make sure that upgrades do not adversely affect existing functionality. That said, if an element or attribute does need to change, we could execute apache rewrites for all old API calls and have the remap function applied to have the output match that of the old markup. Alternatively, the developer could simply modify their API call instead of having to change their codebase to match the markup changes. (Although we do not intend to change existing markup, if we do, we would advise developers to upgrade their code accordingly. That said, rather than having the applications fail during the transition, remap could be used to temporarily handle requests until the full codebase can be upgraded).

Be Fast: Set Up a Comprehensive Caching Architecture
Performance is another critical aspect of APIs when it comes to enticing developers to use them. After all, if the API is sluggish, developers may not want to depend their application on it.

Smart caching of queries and results can really improve the speed of the system. NPR has implemented several layers of caching for the API, as follows:

• Base XML – Caching the full document for each item is important to prevent the system from executing disk I/O before doing any transform. We cache the Base XML first in memory and secondarily as XML files to eliminate the need to access our content database.
• Full Query Results – When compiling the list of items to be returned for any given story, it is important to cache the full list because popular applications that have many concurrent users (such as NPR Addict) are very likely to execute the same queries and expect the same results. The cached result is a single document containing the full list of all items and the full base XML for each.
• Transformed Query Results – The calling application, such as NPR Addict, expects the document to be transformed to fit the application’s needs. So, the results that get cached in Full Query Results may get transformed to MediaRSS while simultaneously removing extraneous fields. Caching the final results that get returned to the calling application enable fastest performance without compromising the system’s ability to use the other caching layers to produce different versions of the document.

Give Them Tools: Provide a Query UI with the Documentation
There are two truths about developers and documentation: the former always expects the latter, but seldom uses it. Of course, you cannot have an API without providing comprehensive documentation. That said, offering a simple user interface that helps developers get what they need from the API wil increase adoption and make life easier for them.

NPR’s API launched with a tool that we call the Query Generator. This tool exposes more than 6500 query-able IDs, methods for controlling the output format, fields to be returned, date and search restrictions, pagination, and more. Using the interface, the developer can select their options and have the tool create the query string for their API request. The developer can also see the results of that query inline before commiting it to their application. Almost exclusively, developers (including the NPR staff) use this tool to create queries, rather than reading the documentation.

Be Open: Eliminate Rate Limiting
Throttling or limiting access to APIs is an inherent disincentive for developers. Moreover, it is actually a detriment to the API provider. After all, the purpose of the API is to grant access to the content. If a given developer can only call the API 5000 times a day, and that developer creates a hugely popular application, the rate-limiting will inherently stifle the developer and the viral nature of the API.

Granted, most APIs use rate-limiting or tiered access levels to allow business people to control the graduation of API users. This seems counter-productive to me though. The better approach is to open access completely, identify those incredibly successful usages, then work with the developer accordingly on a mutually beneficial relationship. This way, applications are given full ability to grow and mature without arbitrary constraints.

Other APIs implement rate-limiting to protect the servers from unexpectedly high load. This is a legitimate risk which, if encountered, can adversely affect the performance of all users. That said, building complicated features into the system, such as rate-limiting, can be much more costly than configuring a scalable server architecture. Moreover, each request to the API will see slight latency increases as a result of the rate-limiting analysis. I know that latency is marginal, but why introduce any additional latency, especially when creating disincentives for developers?

Be Agile: Practice Iterative Development
Building your API over time has several benefits. First, it signals to the developer community that this API is meaningful to the provider and will continue to grow and get supported over time. This sounds trivial, but it is a very important part of the relationship with the community. If developers are not sure about your commitment to the API, are they likely to spend their own time building an application around it?

Another benefit of iterative development is that you do not have to get the API perfect the first time. I will qualify that by saying that, as a matter of principle, any release for an API should be done with the expectation that it will be supported for a long time. This is important because changes to existing API features will break the applications of those that use them. When I say the API doesn’t have to be perfect, I mean it does not have to be complete. New features can (and should) be added over time, extending its capability and making it more attractive for potential developers.

To put it another way, you will not have every detail of the API solved at the initial launch. It is much better to go live with the features that you know well while deferring those that you do not. Trying to cram in tenuous requirements will create headaches for you and for the community down the road. Spend the time necessary on figuring out the features, the supporting markup, the access and error methods, etc. before you commit to an API feature.

Below are the slides from my presentation to the engineering team at PayPal. This presentation discusses the history and future of the Netflix API. It also goes into API design principles as well as concepts behind system scalability and resiliency.

This is link to the video and slides from a presentation that I gave at QCon in San Francisco on April 30, 2012

Daniel Jacobson covers the history of Netflix’s APIs, adaptation for the cloud, development and testing, resiliency, and the future of their APIs.

This article first appeared on Forbes on February 12, 2012

APIs: A Strategy Guide

For most of the past year, I have worked with two brilliant experts on APIs, Daniel Jacobson, at Netflix and Greg Brail, CTO of Apigee, to create a book that clearly explains the value of APIs. In researching the book, APIs: A Strategy Guide, we talked to dozens of other smart people who had led the creation of APIs for both internal and external use.

One of the most striking findings was how often API programs were started in secret, nurtured by the true believers in a clandestine way, slipped into production, and then brought to the awareness of senior management after the API was shown to be a success.

This pattern is understandable but ridiculous. Our book is an attempt to obviate this pattern by providing a top-to-bottom reference for people who want to understand the business value of APIs. But we are not naive. We know that the most likely people to read our book are also true believers and innovators who are already open to new ideas. The trick to accelerating the adoption of APIs and reaping the massive value they can create, is to convince skeptics. At some point, that means convincing the CEO, who, if sold on the idea, can bring all the resources of the organization to bear. APIs have been proven over and over to be a transformative force. It is time for technology leaders to force the issue. So, get yourself a meeting with your CEO and have a conversation along the following lines.

The Business Basics of APIs

When a CEO looks at the calendar entry for your meeting, he or she will likely think, “My god, this seems a bit technical for me. Shouldn’t the CIO or CTO be handling this?” So your first job is to make sure that the CEO understands that APIs are huge channels for business. Start the conversation by pointing out these facts:

APIs are not experimental: More than half of all the traffic to major companies like Twitter and eBay come through APIs

• APIs are channel to new customers and markets: APIs used externally unlock the power of partners to use business assets to extend the reach of your products or services to customers and markets you may not easily reach.
• APIs can be private: Much of the talk about APIs emphasizes their public use. Internal APIs should be part of every companies IT strategy.
• APIs promote innovation: Through an API, people who are passionate about a problem can solve it on their own.
• APIs are a better way to organize IT: APIs used internally can accelerate innovation by allowing everyone in a company to use each others assets without having to wait around for permission.
• APIs are not only for huge companies: The technology is standardized and able to be used by companies of all sizes.
• APIs create a path to lots of Apps: Apps are powered by APIs. When developers are motivated, they can use APIs and combinations of APIs to create new experiences for end users.
• APIs to create lots of apps that can lead to lots of customers: Apps are going to be a crucial channel in the next 10 years. There will be trillions of apps in the next decade vs.a billion web browsers in the last.

Then point the CTO to the post by Google engineer and Amazon alumnus Steve Yegge, that points out that APIs are so important to Amazon CEO Jeff Bezos that he threatened to fire anyone who didn’t expose their assets through APIs.

APIs from Twitter, Amazon, Google, and Facebook have been used to create thousands of applications. These victories are being followed by APIs from AT&T, Sears, E*Trade, Alcatel-Lucent, Accuweather, and hundreds of other companies. Point the CEO to the research from John Musser, founder of ProgrammableWeb.com, a site that tracks the growth of APIs.

At this point if your CEO isn’t interested, then there’s not much you can do.

However, the next question your CEO will likely have is, “What is an API?”

Drawing this simple graphic is a good way to start:

API Value Chain

Explain that APIs are a simple way to provide access to some type of business assets. The business asset can be information itself, information about a product or service, or direct access to the product or service.

Point out that to make an API successful, everyone in the value chain must benefit. Make sure you convey you are not suggesting that if you build an API, the world will come rushing to use it.

The value chain takes many forms. The organization that owns the business asset may or may not be the same as the organization that builds the APIs. Different people or organizations may build, distribute, and market the applications. At the end of the chain are end users who gets the benefit of the business asset. Often, many APIs are used to create a new experience for end users.

Finding your API Value Proposition

If you are getting anywhere with your conversation, your CEO will likely get impatient with the technology and want to know the payoff for your company. He or she may say, “Great, APIs are a big deal, but what does that have to do with us?”

Here’s where you need to come armed with some sort of experiment that you want to get support for. One of the best ways to start is with an internal use of APIs. A key point of our book, one tirelessly championed by Daniel Jacobson, is that internal use of APIs is going to have the largest impact for most businesses. Remember, Amazon’s Jeff Bezos was going to fire people if they didn’t create internal APIs.

So, what are the business assets? Usually information that would benefit the company if more people had it in their hands. Look at the backlog of requests to IT. Is there an API that could take several items off the list? Have this in mind.

It is much better to build skills internally and master the design, development, testing, and operational processes before putting an API in public. That said, with careful planning and a clear value proposition, it is possible to have your first API be a public one, especially if you are following a well-established method of using APIs.

If you do start with an external public API, make sure you have a long testing cycle and flesh out all business and legal concerns before launching. I recently talked about API design and development with Byron Sebastion of Heroku, the Ruby platform for development that was purchased by Salesforce.com in 2010. He said that all of their APIs are first used extensively internally before going through a long public beta test. “When you launch an API, you want to make sure you are confident it is right, because people will rely on it,” Sebastian said.

At this point, I hope you are successful, because then you will need to answer questions about business models, design, engineering, operations, and marketing, all of which are covered in our book.

This article covers one way to go about educating a CEO about APIs. If you have other approaches, please send them along.

Also, we are going to be expanding the book several times this year. If you have a good example of how APIs have been successful for your organization, please reach out to me.

Dan Woods is CTO and editor of CITO Research, a firm focused on advancing the craft of technology leadership. He consults for many of the companies he writes about. For more stories about how CIOs and CTOs can grow visit CITOResearch.com.

This article originally posted by Scott Fulton on ReadWriteWeb on February 3, 2012 as Part II in a series. Part I can be found here.

What we today call the “mobile app” could, in a very short period of time, become known as the portable app, or just the “app.” It tends to use such a simple and straightforward model of interaction that people are starting to prefer using their smartphones for certain tasks, even when their PCs are right in front of them. By this time next year, portable apps originally designed for use on smartphones and tablets may be running on laptops.

The extent to which this changes everything is a topic that no one, not even ReadWriteWeb, has fully fathomed. The Web as we have come to know it will be affected significantly. What users have come to know as Web sites will be willingly and eagerly substituted with Web apps. In Part 2 of our interview with the co-author of APIs: A Strategy Guide, Netflix lead API engineer Daniel Jacobson tells us the one huge difference between an app and a site involves the extent to which they rely on an API. It is part of every app’s DNA.

The First, Painful Steps Toward Multi-Platform

In 2002, as you learned from part 1 of our RWW interview last week, when Jacobson was with NPR, he helped make a critical decision about its information infrastructure, the implications of which his team had not foreseen: “Literally the first thing that we did,” he tells RWW, “is, we built the API and we put the Web site on top of it. So the Web site runs off the API. It’s a little bit of a different interaction model; it doesn’t have to go through the authentication and whatever else, in the same way that external apps do.”

That API later gave NPR the freedom to build apps that run outside the browser, and that use that same API in different ways. So when mobile apps were invented, NPR was among the first publishers to be ready for them. When Netflix saw it needed an architecture that enabled it to reach all its users without it being dependent upon the usage model for any one device, including the Web browser, it hired Jacobson to build it.

A 2005 Netflix demo at a Microsoft convention featured one of that company’s program managers at the time, Darryn Dieken, showing then-President Jim Allchin the prospects of using one underlying technology as the foundation for developing a unified product line across different devices. The technology at the time was code-named “Avalon,” and evolved into what we now call Silverlight.

After showing how a Netflix product selector ran outside the browser but through the Web, in a way people had never seen before at that time, Dieken showed essentially the same selector running inside Windows Vista on a tablet PC. From there, he proceeded to show where else folks would eventually find Netflix.

The demo took the audience inside Windows Media Center, which had just been released for Windows XP and was being vastly updated for Vista. The Media Center plug-in used many of the same presentation techniques and concepts as the stand-alone version, demonstrating the benefits of code reuse.

But when the demo turned its attention to Netflix on a Windows Mobile phone, it became painfully obvious that the benefits of client-side code reuse could only go so far. Yes, there was communication taking place between all these different clients and the server. But the way these interactions were happening were based on leveraging Web site-oriented, forms-based submissions that at one level could be described as an API, but failed to be uniform – one API for many platforms.

The goal of any modern API, Dan Jacobson emphasizes, is “to treat any presentation layer the same. So if you have multiple Web sites, like NPR does (they have NPR Music as well as NPR.org), both of those sites run off of the same interaction model through the API. They’re just presentation layers, the same way as mobile app or Google TV or [NPR] Infinite Radio. Users are going to consume new material in any way that they want to, wherever, whenever; and your goal as publisher is to make sure that you have a presentation layer that serves them wherever that is. And in doing so, the easiest way, the most effective way to date is to leverage APIs, and invest a little bit on having the right talent surrounding it.”

“Publish Everywhere” Doesn’t Have to Be Homogenous

Because presentation layers are so different from one another, he goes on, a business can and should nurture teams of developers with the exclusive skillsets that each of those layers needs – for example, Objective-C developers for iPhone apps. There’s no reason why certain teams can’t specialize. Having a single API that addresses each layer in a standard way, he says, provides all your teams with the flexibility they require to take advantage of the platforms on which they’re focused.

This allowance for specialization tends to work itself away from the “one Web” way of thinking, the belief that everything will inevitably merge into HTML5. In professing that API design should not be centered around any one single mode of presentation, lest it eventually become obsolete (among other reasons), Jacobson advises that API designers focus on finding ways to symbolize and encode business interactions, the things that businesses do, not the things that Web sites do. Your goal is not to make the browser more efficient or the user experience more immersive. Leave that to the UX designers. As the API engineer, your goal is to enable business.

“That kind of thinking is fundamentally different than, ‘How do I want to structure my content? Do I need to think about what resources can be broken up in which ways and made available in different ways?’” says Jacobson. “For NPR, for example, there are stories, there are assets, different kinds of things in that system. For Netflix, there are users, catalog items. How do you want to structure that material, both in terms of the resource level as well as items underneath it? What are the rights management concerns that go into this, legal constraints internally about what can be published? For Netflix, what can I show users in Latin America that I can’t show to people in Canada? For NPR, it’s, I’m publishing AP photos; whom can’t I present that to, and whom can I? Those kinds of things are really business-oriented decisions that you can’t just flip a switch and say, ‘Make it happen.’ You need to be very thoughtful about what you’re exposing and to whom, and how you’re going to do it so you can get the maximum effectiveness out of it.”

It is this concept which may outmode, or render obsolete, the traditional notion of the Web site, the notion that something that’s created once and published everywhere (COPE) must always be the same thing. Done properly, Jacobson says, it can and should be integrated with the uniqueness of each device.

“When Web APIs started out, they tended to be more about publishing on all kinds of different platforms. Now I think it’s very much about aggregation, and merging others’ API experiences,” says the Netflix engineer. “One of the interesting things with Netflix, for example: We have branded apps on a wide range of platforms, and if you look at something like AppleTV or Roku or Xbox, or any of these other devices, we’re not the only ones there. There is an aggregation of services where Netflix creates an experience on that platform. We actually integrate with their systems, we’re creating an experience on that site, and then people can access our experience in the way they expect it to be presented.”