# ISSN required for conference proceedings?

**URL:** <https://community.crossref.org/t/issn-required-for-conference-proceedings/3041>\
**Category:** Content Registration\
**Tags:** content-registration, xml\_support, conference, issn\
**Created:** [18 October 2022 21:51 UTC](https://community.crossref.org/t/issn-required-for-conference-proceedings/3041 "2022-10-18T21:51:57Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![adamread](https://avatars.discourse-cdn.com/v4/letter/a/7cd45c/32.png) [@adamread](https://community.crossref.org/u/adamread)\
**Post date:** [18 October 2022 21:51 UTC](https://community.crossref.org/t/issn-required-for-conference-proceedings/3041/1 "2022-10-18T21:51:57Z")

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I am trying to strip down the example XML for proceedings series metadata to the metadata I actually have. The programs for the conferences I want to register don’t have an ISSN (or ISBN). If I remove the tag from the \<proceedings\_series\_metadata\> section, the validator fails:

File: TestConference.xml

[Error] :34:33: cvc-complex-type.2.4.a: Invalid content was found starting with element ‘noisbn’. One of ‘{“Link ToJATS”:abstract, “LinkToSchema”:issn}’ is expected.

I don’t’ understand the abstract expectation, since they aren’t present in that section anyway. I also have 73 years worth of conferences with no associated ISSN. Is there any way to get around this?

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**Author:** ![adamread](https://avatars.discourse-cdn.com/v4/letter/a/7cd45c/32.png) [@adamread](https://community.crossref.org/u/adamread)\
**Post date:** [18 October 2022 22:02 UTC](https://community.crossref.org/t/issn-required-for-conference-proceedings/3041/2 "2022-10-18T22:02:22Z")

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A little more digging and I’ve answered my own question:  
Apparently a “proceedings series” is a serial publication, like a journal, and not an annual series of conferences.

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**Author:** ![Shayn](https://sea2.discourse-cdn.com/flex020/user_avatar/community.crossref.org/shayn/32/57_2.png) [@Shayn](https://community.crossref.org/u/Shayn)\
**Post date:** [18 October 2022 22:50 UTC](https://community.crossref.org/t/issn-required-for-conference-proceedings/3041/3 "2022-10-18T22:50:47Z")

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Hello,

Generally speaking, those errors that begin “cvc-complex-type.2.4.a: Invalid content was found starting with element…” mean that either some metadata element is missing or that the elements are out of order. But the details can vary a lot - confusingly, it’s not always exactly the element that’s named in the error message that’s the problem. So, if you’re having persistent trouble with errors like that, please email [support@crossref.org](mailto:support@crossref.org) and attach a copy of the xml file, so we can have a look at it directly.

ISSNs are required if you’re registering a conference proceedings that published within a conference series. Because, exactly like you said, a conference series is a serial publication the same way that a journal is a serial publication. A conference series is almost always derived from an annual series of conference. So, if you do host an annual series of conferences, and publish a proceedings for each one, it’s beneficial to register them as a series and apply for an ISSN for it.

But, you can register individual conference proceedings on their own, without including any series-level metadata. In that case, no ISSN is required.