Communications - August 2012

French government agency INSEE ( National Institute of Statistics and Economic Studies; http://www.insee.fr), created in the middle of the 20th century, is in charge of conducting all sorts of statistical analyses of the population and economy. INSEE has become an important open data provider.

Surprisingly, the data might be
endogenous, too. Google’s flu trends
analysis is a remarkable example of
this kind. Google researchers have ob-
served that the number and locales of
search requests about flu is strongly
related to the propagation of the ill-
ness. 2 Google makes this data avail-
able country by country, making it easy
for anyone to implement applications
using these statistics.

Figure 10. Visualizing the flu propagation worldwide.

(module flutrend (import (gchart "gchart-api- 1.0.*.hz")))

(<HTML> ˜(define sources

(<IMG> :src (google-chart :type ’map :area ’europe)

:onload ˜(when (pair? sources)

(after 300

(lambda ()

(set! this.src (car sources))

(set! sources (cdr sources)))))))

Figure 1: Visualizing the Flu propagation world wide.

Figure 11. Reacting to SMS.

ate a video showing the propagation of the flu over time. This is mostly a tool-combination problem since all the hard work can be delegated to external parties. Thus, the work shown here consists only of collecting, combining, and reusing all the tools and data at our disposal. The actual Hop implementation, shown in Figure 10, counts no more than 15 lines of code.

The application code relies on a binding that makes the Google Chart API directly accessible from Hop. This Web API creates all kinds of charts and geographical maps, generating images according to the arguments specified on appropriate URLs. This API is combined with the extraction of flu statistics. First, image URLs are generated out of statistical values parsed using a Hop spreadsheet-elements library. Then images generated on the fly by Google Chart are displayed one after the other, every 300 milliseconds.

This example shows that new and deep knowledge might emerge when the ability to collect, compare, and analyze vast sets of open data is easily accessible. Hop is specifically geared toward this objective, with composition and reuse as the two central features.

(module androidemo (library mail phone hopdroid))

(define android (instantiate::androidphone))

(define tts (instantiate::androidtts (phone android)))

(define-service (phone/sms)

(define speak #t)

(add-event-listener! android "sms-received"

(lambda (e::event)

;; function invoked on the server (i.e., the phone)

;; upon sms-reception

(let ((val e.value))

;; broadcast to all clients the reception of the sms (hop-event-broadcast! "sms" val)

;; speak out the sms content on the phone (when speak (tts-speak tts (cadr val))))))

;; create two empty HTML elements that will be filled ;; upon SMS reception

(let ((sms-num (<TD>))

(sms-body (<TD>)))

(<HTML> ˜(add-event-listener! server "sms"

;; function invoked on the client (i.e., a web browser)

;; upon reception of the server "sms" event

(lambda (e)

;; insert the calling number in the HTML page

(innerHTML-set! $sms-num (car e.value))

;; insert the SMS content in the HTML page

(innerHTML-set! $sms-body (cadr e.value))))

(<TABLE> (<TR> sms-num sms-body))

(<BUTTON> :onclick ˜(with-hop ($(service () (set! speak (not speak))))) "mute/speak"))))

Figure 1: Reacting to SMS.

Bigger than the Web

The human Web can be made even bigger by binding sensors from and actuators to the physical environment, such as those provided by smartphone sensors, multimedia equipment, home or automotive automation equipment, and the countless other electronic devices that surround us. However, only the most popular of these sensors will be natively supported by the next Web browsers. For example, the incoming versions of the Firefox and Chrome navigators have announced support for video and audio capture; accessing other remote equipment through browsers or programmed applications will still require third-party support. The Hop philosophy is to migrate the remote interface facilities to the server, give the user full Hop programming power on the associated data, and deliver results to clients in the standard way when using browser-based interfaces.