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Objective

Process events to provide semantic translation for later processing

Setup

• Complete the Foursquare Checkin exercise. 
• Complete the Data Storage exercise.

Exercise

1. Create an event channel and label it "current location"
2. Use the event channel ID to create an ESL that raises a location:current event with lat-long attributes
3. Modify the location rule in the Personal Data Storage exercise to also store lat-long attributes from a Foursquare checkin
4. Create and register a ruleset:
   1. Write a rule called nearby that listens for the current:location event. 
   2. Use the great circle functions in the math library to calculate the distance between the lat-long coordinates from the PDS module and those reported with the location:new_current event. 
   3. If the distance is less than a threshold (say 5 miles), then raise a explicit:location_nearby event otherwise raise a explicit:location_far event. Both events should contain the distance as an attribute. 
5. Install the ruleset you created in the preceding step
6. Create and register a second ruleset that has a rule that listens for the location:nearby event that sends a text message (see the Twilio module documentation) with the distance to your phone. Make sure you install this ruleset as well. 
7. Test by raising the location:new_current event using the ESL you designed. Be sure you've checked in with Foursquare since modifying the ruleset to store lat-long data. 

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