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This document is meant to show the different reasons to choose either the API or web services
API
For the API the external application installs the API jar in their application and could connect to a single OpenMRS database if they had the proper credentials in their runtime properties file
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For an external application to get or put data into an OpenMRS instance via web services, you have to install the webserviceswebservices.rest module in the OpenMRS instances and then program the application to make the appropriate calls in JSON or XML format over HTTP to the web services module.
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