API
API
[Cueball sitting at a desk staring at a computer screen.] API Guide Request URL format: http://~~~.com/<username>/<item ID>
Server will return an XML document which contains: The requested data. Documentation describing how the data is organized spatially.
API Keys To obtain API access, contact the X.509-authenticated server and request an ECDH-RSA TLS key... If you do things right, it can take people a while to realize that your "API documentation" is just instructions for how to look at your website.

This comic presents a web site designed for human readers as if it had an API ( application programming interface ) designed for machine-to-machine web service . An API is a set of instructions about a computer program, intended to be used by developers of other computer programs, so the two programs can interoperate more easily. The documentation explains how to send commands to the program, and how the output will be returned.
Many web APIs are designed to return data in XML format. But in this case, the XML is XHTML , a version of the language that is used by most web pages. The "requested data" is the actual content (e.g. a blog post), and "documentation" refers (in an obscure way) to the parts of a web page that control how it looks on the screen (e.g. CSS and perhaps JavaScript layout code). The
"documentation" may also be DTD which tells the XML parser info about this particular XML format, i.e. XHTML.
In order for a program to process a generic web site designed for human viewing, the program needs to use web scraping techniques, which often break when the web site design changes in subtle ways that a human might never notice. Therefore, developers prefer to have proper APIs with well-defined machine-readable formats, stable interfaces and documentation that actually describes the semantics of the data.
For example, Google has an official API for version 3 of their Youtube web service . But developers who don't want to hassle with the required API key or the costs associated with its use sometimes just scrape the regular YouTube web site . So someone could publish this comic with a YouTube URL as a convoluted hint to developers that there is an alternative to the official API.
The API keys section is a step-by-step description of how a web page is protected with HTTP Secure (HTTPS). The Transport Layer Security (TLS) protocol uses an elliptic curve Diffie–Hellman (ECDH) key signed using Rivest-Shamir-Adleman (RSA) encryption, which is stored in an X.509 certificate. Normally, the browser or operating system does this behind the scenes, so most web developers and users do not need to know these details.
The access limits mentioned in the title text says that the API can be used for 86,400 seconds each day. At first this may appear to be a strange arbitrary number, however it is in fact the total number of seconds in 24 hours, essentially meaning there is no limit on most days. The International Earth Rotation and Reference Systems Service (IERS) is the organization that decides when to add leap seconds , which account for slight anomalies in the Earth's rotation as compared to the mean solar day . These leap seconds will mean that the website is available for one extra second occasionally, although IERS decisions are based on actual Earth rotation rates and they of course wouldn't respond to requests for leap seconds in order to lengthen the number of seconds that a web site would be available for in a given calendar day.  The API does not discuss the issue that some days have 23 or 25 hours due to daylight saving time in the U.S. and summer time in Europe and some other places. This suggests that the web service tracks time via UTC .
[Cueball sitting at a desk staring at a computer screen.] API Guide Request URL format: http://~~~.com/<username>/<item ID>
Server will return an XML document which contains: The requested data. Documentation describing how the data is organized spatially.
API Keys To obtain API access, contact the X.509-authenticated server and request an ECDH-RSA TLS key... If you do things right, it can take people a while to realize that your "API documentation" is just instructions for how to look at your website.
