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Purpose

We would like to be able to determine how fresh is the data on HDX for two purposes. Firstly, we want to be able to encourage data providers to make regular updates of their data where applicable, and secondly, we want to be able to tell users of HDX how up to date are the datasets in which they are interested.

Progress

It was determined that a new field was needed on resources in HDX. This field shows the last time the resource was updated and has been implemented and released to production

Jira Legacy
serverJIRA (humanitarian.atlassian.net)
serverIdefab48d4-6578-3042-917a-8174481cd056
keyHDX-4254
. Related to that is ongoing work to make the field visible in the UI
Jira Legacy
serverJIRA (humanitarian.atlassian.net)
serverIdefab48d4-6578-3042-917a-8174481cd056
keyHDX-4894
.

Critical to data freshness is having an indication of the update frequency of the dataset. Hence, it was proposed to make the data_update_frequency field mandatory instead of optional and change its name to make it sound less onerous by adding "expected" ie. dataset expected update frequency 

Jira Legacy
serverJIRA (humanitarian.atlassian.net)
serverIdefab48d4-6578-3042-917a-8174481cd056
keyHDX-4919
. It was confirmed that this field should stay at dataset level as our recommendation would be that if a dataset has resources with different update frequencies, it should be divided into multiple datasets. Assuming the field is a dropdown, it could have values: daily, weekly, fortnightly, monthly, quarterly, semiannually, annually, never. It would be good to have something pop up if the user chooses "never" making it clear that this is for datasets for which data is static. We will have to audit datasets where people pick this option as we don't want people choosing "never" because they don't want to commit to putting an expected update frequency. The expected update frequency requires further thought particularly on the issue of static datasets, following which there will be interface design and development effort. 

A trigger has been created for Google spreadsheets that will automatically update the resource last modified date when the spreadsheet is edited. This helps with monitoring the freshness of toplines and other resources held in Google spreadsheets and we can encourage data providers to use this where appropriate. Consideration has been given to doing something similar with Excel spreadsheets, but support issues could become burdensome.

Important fields


FieldDescriptionPurpose
data_update_frequencyDataset suggested expected update frequencyShows how often the data is expected to be updated or at least checked to see if it needs updating
revision_last_updatedResource last modified dateIndicates the last time the resource was updated irrespective of whether it was a major or minorchangeminor change
dataset_dateDataset dateThe date referred to by the data in the dataset. It changes when data for a new date comes to HDX so may not need to change for minor updates

Approach

  1. Determine the scope of our problem by calculating how many datasets are locally and externally hosted. Hopefully we can use the HDX to calculate this number.  
  2. Collect frequency of updates based on interns work? 
  3. Define the age of datasets by calculating: Today's date - last modified date 
  4. Compare age with frequency and define the logic: how do we define an outdated dataset

Determining if a Resource is Updated

The method of determining whether a resource is updated depends upon where the file is hosted. If it is in the file store, then the update time is clear,
If it is hosted externally, then it is not so simple. It may be possible to use HTTP get the last_modified field depending upon whether the server supports it or not.

Number of Files Locally and Externally Hosted

TypeNumber of ResourcesPercentageExample
File Store                                  2,102
22%

CPS                                  2,459
26%

HXL Proxy                                  2,584
27%

ScraperWiki                                     162
2%

Others                                  2,261
24%

Total                                  9,568
100%

Classifying the Age of Datasets


Thought has previously gone into classification of the age of datasets. Reviewing that work, the statuses used (up to date, due, overdue and delinquent) and formulae for determining those statuses is sound and so we will build on that foundation:


Update Frequency

Dataset age state thresholds

(how old must a dataset be for it to have this status)

Up-to-date

Due

Overdue

Delinquent

Daily

0 days old

1 day old

due_age = f

2 days old

overdue_age = f + 2

3 days old

delinquent_age = f + 3

Weekly

0 - 6 days old

7 days old

due_age = f

14 days old

overdue_age = f + 7

21 days old

delinquent_age = f + 14

Fortnightly

0 - 13 days old

14 days old

due_age = f

21 days old

overdue_age = f + 7

28 days old

delinquent_age = f + 14

Monthly

0 -29 days old

30 days old

due_age = f

44 days old

overdue_age = f + 14

60 days old

delinquent_age = f + 30

Quarterly

0 - 89 days old

90 days old

due_age = f

120 days old

overdue_age = f + 30

150 days old

delinquent_age = f + 60

Semiannually

0 - 179 days old

180 days old

due_age = f

210 days old

overdue_age = f + 30

240 days old

delinquent_age = f + 60

Annually

0 - 364 days old

365 days old

due_age = f

425 days old

overdue_age = f + 60

455 days old

delinquent_age = f + 90



Thoughts

There are two aspects of data freshness:

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