2000115-Strengthening-Communities-with-Neighborhood-Data

Progress in Data and Technology 123
nearby restaurants, and the user’s preferences are pulled from another. It
matters not at all whether the provider of restaurant data uses completely
different tech platforms than the provider of food preference data. All that
matters is that they both quickly deliver data in a machine-readable format
after submitting a valid service request. The most famous mashup factory
in existence today is the ubiquitous Google Map, which combines the customer’s
personal data—a file in Keyhole Markup Language (KML) format
on a local device—with Google’s Map engine.
Mashups work because data providers publish APIs. An API is essentially
a contract to deliver a specified data product in a specified format
in response to a valid request. Some APIs are freely accessible to all,
while others come with a cost. APIs work because the Internet works.
That is, HTTP (hypertext transfer protocol) facilitates the transport of a
relatively large amount of information over a wired or wireless network.
Request in, data out. The network is the highway; HTTP is the transport
company. APIs accept the customer’s order and ship the goods. It’s up
to the receiver to do something with those goods. Twitter’s API is a good
example. If you want to find all tweets marked with the hashtag #nnip,
you can call the Twitter API and receive a list of those tweets.
But you probably wouldn’t do that unless you were an experienced
web developer. More likely, you’d open your mobile phone and use an
app created by a web developer. You would type #nnip and click Go and
the list would appear. Raw data transformed by a high-skill technician
appears as a finished product for the consumer.
The mashup’s chain of events typically follows a pattern of this kind:
• The user navigates to a web page by using a browser.
• The web browser contacts a web server for the page content.
• The web server pulls data from a local database, but also requests
additional data from a remotely hosted API.
• The user’s browser displays the now-hybridized content (pulled
from two or more servers), including clickable options for further
exploring.
• With each click from the user, the browser itself initiates API
requests for more data from remote servers.
• The new data are displayed in a section of the web page, but the
web page itself does not need to reload when this occurs.
• The process can go on indefinitely without the user ever needing
to reload the web page.