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General Concepts

Study, Survey​

A Study, for this system is a set of surveys working together, associated to a set of Participants.

Survey System​

The Survey System is the set of the Survey Engine and the Study Service.

The Survey Engine is the client part, dedicated to run a survey using a Survey Definition and sending the response to the Study Service

The Study Service is the backend part, with several roles, it manages and provides Survey Definition and Survey Context to a Survey Engine client, it processes event based rules (like when a survey response is submitted) and run the survey timer to update the participant state.

Survey Definition​

A Survey Definition is a formal document specifying a survey. The survey definition embeds the survey structure (organization of item and groups), survey components (display or data collection), translations and logic (using Expressions). Survey definition is represented in JSON format.

A Survey is run by the Survey Engine, along with a Survey Context (extra information about the run, like participant flags.)

Expression​

An expression is the way survey and study logic are described. An expression can be evaluated to describe a condition (on question, on response data), to trigger operation with side effect (in a survey, for example triggering a question to be shown, or in a study for example to add assign a new survey to be filled to a participant or trigger a message sending).

Three kind of Expression are used in the system:

  • Survey Expression (evaluated by Survey Engine on client side, during the survey running.
  • Study Expression & Study Action (evaluated by the Study Service, triggered by study event, like response submission).

Survey and Study Expression are evaluated to a value (like boolean, string, number), like a function.

Study Action, are not evaluated to a value, but are updating the Participant state (flags, assigned surveys) and can trigger some external actions (like sending a message to the participant or to the "team" holding the running the platform).

All expressions share the same structure, described in the following page

Participant​

A participant, is the subject of the data collection. In this Survey system, a *participant** is only represented by a set of properties giving a persistent state for the subject of the data collection (they are mostly defined by the study/survey designer, we dont manage credentials, login, username here,). So participant is an abstract concept to design a context/state of a subject in a study/survey. It can be a human, or not depending of the study.

Participants and associated data are described in Study service

Localized Text​

The Survey Definition includes translations for all text to be presented to the user. The texts are provided in a little structure associating text and language code called Localized Text. A survey can contain the translations for several languages. Many fields in a Survey Definition contains this kind of structure containing all the translations.