# Blog

## DOIs and matching regular expressions

Andrew Gilmartin – 2015 August 11

We regularly see developers using regular expressions to validate or scrape for DOIs. For modern Crossref DOIs the regular expression is short

/^10.\d{4,9}/[-._;()/:A-Z0-9]+\$/i

For the 74.9M DOIs we have seen this matches 74.4M of them. If you need to use only one pattern then use this one.

## Rehashing PIDs without stabbing myself in the eyeball

Geoffrey Bilder – 2015 June 11

Anybody who knows me or reads this blog is probably aware that I don’t exactly hold back when discussing problems with the DOI system. But just occasionally I find myself actually defending the thing…About once a year somebody suggests that we could replace existing persistent citation identifiers (e.g. DOIs) with some new technology that would fix some of the weaknesses of the current systems. Usually said person is unhappy that current systems like

## Coming to you Live from Wikipedia

Joe Wass – 2015 May 20

We’ve been collecting citation events from Wikipedia for some time. We’re now pleased to announce a live stream of citations, as they happen, when they happen. Project this on your wall and watch live DOI citations as people edit Wikipedia, round the world.

## View live stream »

In the hours since this feature launched, there are events from Indonesian, Portugese, Ukrainian, Serbian and English Wikipedias (in that order).

## January 2015 DOI Outage: Followup Report

Geoffrey Bilder – 2015 March 17

## Background

On January 20th, 2015 the main DOI HTTP proxy at doi.org experienced a partial, rolling global outage. The system was never completely down, but for at least part of the subsequent 48 hours, up to 50% of DOI resolution traffic was effectively broken. This was true for almost all DOI registration agencies, including Crossref, DataCite and mEDRA.

At the time we kept people updated on what we knew via Twitter, mailing lists and our technical blog at CrossTech. We also promised that, once we’d done a thorough investigation, we’d report back. Well, we haven’t finished investigating all implications of the outage. There are both substantial technical and governance issues to investigate. But last week we provided a preliminary report to the Crossref board on the basic technical issues, and we thought we’d share that publicly now.

## Real-time Stream of DOIs being cited in Wikipedia

Joe Wass – 2015 March 03

## TL;DR

Watch a real-time stream of DOIs being cited (and “un-cited!” ) in Wikipedia articles across the world: http://goo.gl/0AknMJ

## Background

For years we’ve known that the Wikipedia was a major referrer of Crossref DOIs and about a year ago we confirmed that, in fact, the Wikipedia is the 8th largest refer of Crossref DOIs. We know that people follow the DOIs, too. This despite a fraction of Wikipedia citations to the scholarly literature even using DOIs. So back in August we decided to create a Wikimedia Ambassador programme. The goal of the programme was to promote the use of persistent identifiers in citation and attribution in Wikipedia articles. We would do this through outreach and through the development of better citation-related tools.

## Crossref’s DOI Event Tracker Pilot

Geoffrey Bilder – 2015 March 02

## TL;DR

Crossref’s “DOI Event Tracker Pilot”- 11 million+ DOIs & 64 million+ events. You can play with it at: http://goo.gl/OxImJa

## Tracking DOI Events

So have you been wondering what we’ve been doing since we posted about the experiments we were conducting using PLOS’s open source ALM code? A lot, it turns out. About a week after our post, we were contacted by a group of our members from OASPA who expressed an interest in working with the system. Apparently they were all about to conduct similar experiments using the ALM code, and they thought that it might be more efficient and interesting if they did so together using our installation. Yippee. Publishers working together. That’s what we’re all about.

## Problems with dx.doi.org on January 20th 2015- what we know.

Geoffrey Bilder – 2015 January 21

So today (January 20th, 2015) the DOI HTTP resolver at dx.doi.org started to fail intermittently around the world. The doi.org domain is managed by CNRI on behalf of the International DOI Foundation. This means that the problem affected all DOI registration agencies including Crossref, DataCite, mEDRA etc. This also means that more popularly known end-user services like FigShare and Zenodo were affected. The problem has been fixed, but the fix will take some time to propagate throughout the DNS system. You can monitor the progress here:

https://www.whatsmydns.net/#A/doi.org

Now for the embarrassing stuff…

## Introducing the Crossref Labs DOI Chronograph

Joe Wass – 2015 January 12

At Crossref we mint DOIs for publications and send them out into the world, but we like to hear how they’re getting on out there. Obviously, DOIs are used heavily within the formal scholarly literature and for citations, but they’re increasingly being used outside of formal publications in places we didn’t expect. With our DOI Event Tracking / ALM pilot project we’re collecting information about how DOIs are mentioned on the open web to try and build a picture about new methods of citation.

## Linking data and publications

Geoffrey Bilder – 2014 September 21

Do you want to see if a Crossref DOI (typically assigned to publications) refers to DataCite DOIs (typically assigned to data)? Here you go: http://api.labs.crossref.org/graph/doi/10.4319/lo.1997.42.1.0001 Conversely, do you want to see if a DataCite DOI refers to Crossref DOIs? Voilà: http://api.labs.crossref.org/graph/doi/10.1594/pangaea.185321 Background “How can we effectively integrate data into the scholarly record?” This is the question that has, for the past few years, generated an unprecedented amount of handwringing on the part researchers, librarians, funders and publishers.

## Citation needed

Geoffrey Bilder – 2014 August 07

Remember when I said that the Wikipedia was the 8th largest referrer of DOI links to published research? This despite only a fraction of eligible references in the free encyclopaedia using DOIs. We aim to fix that. Crossref and Wikimedia are launching a new initiative to better integrate scholarly literature in the world’s largest public knowledge space, Wikipedia. This work will help promote standard links to scholarly references within Wikipedia, which persist over time by ensuring consistent use of DOIs and other citation identifiers in Wikipedia references.