# What is the difference between period and duration?

**Category:** [RM](https://discourse.openehr.org/c/rm/42)
**Created:** 2024-09-03 03:22 UTC
**Views:** 211
**Replies:** 5
**URL:** https://discourse.openehr.org/t/what-is-the-difference-between-period-and-duration/5653

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## Post #1 by @linforest

Within one of the contents in a Composition instance for physical activity observations, there are two elements following the element **/content/data/origin**, i.e.,  **period** and **duration**.  What is the difference between the two?   Is **period** intended to represent Periodicity?   Thanks.

```
    <data archetype_node_id="at0001">
      <name>
        <value>Event Series</value>
      </name>
      <origin>
        <value>2024-09-02T04:25:06</value>
      </origin>
      <period>
        <value>PT0S</value>
      </period>
      <duration>
        <value>PT0S</value>
      </duration>
```
![image|690x334](upload://thH8wl7lkcU5P8pAyt4ujowvq3Z.png)

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## Post #2 by @thomas.beale

Period is the repeating period of samples in the series, e.g. 1 second, 1 minute etc - it the series is periodic. Duration is the total duration of each event. 

[Some diagrams showing the use of these attributes](https://specifications.openehr.org/releases/RM/development/data_structures.html#_timing).

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## Post #3 by @linforest

Indeed, I need to re-view the Overview.   Haha, it just so happens that I was just reading [this section and illustration](https://specifications.openehr.org/releases/RM/development/data_structures.html#_timing).  Thank you so much.

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## Post #4 by @joostholslag

Dear Lin,

You ask a lot of good questions. I’m sure many people wonder for the answer but do not make the effort to ask. I hope you are satisfied with the answers provided by the community’s experts. 
For a long time this community has wanted to lower the barrier of entry to understanding openEHR. Do you have any suggestions how to keep these valuable interactions for future newcomers?
I’m thinking of collecting them as an FAQ, changes to the spec text or indexing them in the new to openEHR topic.

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## Post #5 by @linforest

Good idea!
And it reminds me of another great online course "[OBO Semantic Engineering Training](https://oboacademy.github.io/obook/)".  Maybe we can also create and maintain such an online course / starter guide etc. for the community.
Thank you so much!

![image|690x299](upload://rgDuo3RQYYNppFirmq0rPTVxkcI.png)

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## Post #6 by @richard.kavanagh

@joostholslag I've been having similar conversations. A potential idea was along the lines of this resources (for FHIR) https://darrendevitt.com/

But clearly for openEHR - would probably need curation and a good search engine.
Extra smarts for attaching an LLM :slight_smile:

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**Canonical:** https://discourse.openehr.org/t/what-is-the-difference-between-period-and-duration/5653
**Original content:** https://discourse.openehr.org/t/what-is-the-difference-between-period-and-duration/5653