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--- documentation:next_cdm:location_history [2016/06/09 21:44] – created cgreich
+++ documentation:next_cdm:location_history [2016/10/14 18:15] (current) – [Table] gowtham_rao
@@ Line 1: / Line 1: @@
 ===== Location History =====
-  * Requester: Robert Mill
+  * Requester: Robert Miller
   * Discussion: [[http://forums.ohdsi.org/|here]].
 ----
 === Proposal ===
+The location_id in the Person table is only capable of storing a single location address for an individual. We want to know where a person's location was for a given date-time. This maybe solved using a location_history table, which acts as a relational entity between Person and Location.
+There are several things to consider here:
+  * An entity (person, care site, device) may change locations over a period of time
+  * A location may have multiple entities (person, device, care site) over a period of time
+  * An entity may have more than one locations at the same time (e.g. vacation home for a person, or mailing address vs residing address vs billing address, beneficiaries address vs. subscribers address)
+The first two issues maybe solved easily. The third, if we are concerned about it, may be resolved by adding an location type field e.g ("primary residence").
+Note in the table below: both person and location IDs do not need to be unique in the residency table.
+| **location_history_id**  | **person_id**  | **location_id**  | **start_date**  | **start_time**  | **end_date**  | **end_time**  |
+| res1                     | John Doe       | location1        | May 1985        | 24:00           | -             | -             |
+| res2                     | Jane Doe       | location1        | May 1985        | -               | -             | -             |
+| res3                     | Bob Smith      | location2        | July 2011       | -               | June 2012     | -             |
+| res4                     | Bob Smith      | location3        | July 2012       | 14:55           | August 2012   | 21:00         |
+It was agreed that the location_id in person table would represent the current location of the person.
+It was discussed that location_history may need to be generalized to include device, care site, provider etc. **How do we do that?**
+| **location_history_id**  | **entity_domain_id**  | **entity_id**   | **location_id**  | **start_date**  | **start_time**  | **end_date**  | **end_time**  |
+| res1                     | person                | person_id_1     | location1        | May 1985        | 24:00           | -             | -             |
+| res2                     | provider              | provider_id_1   | location1        | May 1985        | -               | -             | -             |
+| res3                     | care_site             | care_site_id_1  | location2        | July 2011       | -               | June 2012     | -             |
+| res4                     | person                | person_id_2     | location3        | July 2012       | 14:55           | August 2012   | 21:00         |
 ----
 === Use Cases ===
+  * What zip code did person x live in when they were diagnosed with y?
+  * Are people who live closer to x more likely to y?
+  * Is there a cluster of people with certain conditions, when did that cluster first occur, and has it changed in location over time
+  * How do care sites compare in terms of average travel time? Does it matter?
+  * Are there hot spots for specific conditions?