This page serves to collect quality criteria for metadata records (and - by extension - profiles). 

There has been a number of such lists proposed, we aim to gather them here in one place.

== Related work

* [[CmdiBestPracticeGuide#Qualitycheck-list]] (criteria from there moved to this list)
* [[MDQAS]] older draft for specifying a MD quality assessment service (criteria from there moved to this list)
* [[Curation Module]] will operationalize the defined quality criteria and allow to check metadata records if they adhere to these criteria 
* [http://www.lrec-conf.org/proceedings/lrec2014/pdf/1011_Paper.pdf LREC2014 paper] by Thorsten Trippel et al.  Towards automatic quality assessment of component metadata 
* Technical report by Marc Kemps-Snijders (2014): Metadata Quality Assurance 


== Criteria

(Aspects with questionmark are subject to discussion) 

=== Schema level

strict criteria:
* ratio of elements with data categories
* presence of "required" data categories
* coverage of mapping to vlo facets 
  (possibly weighting of facets)


soft: 
* public accessibility of the profile
* status of the concept (approved/candidate/deprecated/...)
* number of defined elements (identify a range - too many, too little)
* number of unique components used
* total number of components used
* number of references to distinct data categories defined externally


=== Instance level

strict:
* availability of the (reference to) schema 
  (i.e. both there is a reference to schema and the schema can be retrieved)
* Does the schema reside in the Component Registry
* validity of the record wrt to the schema
* are the header fields complete?
 * is there a unique !MdSelfLink?
 * is there an !MdCollectionDisplayName? 
 * is there a !MdProfile?
* does it contain !ResourceProxy elements?
  * link to a LandingPage when available?
  * is there an indication of the mime type? 
  * ResourceProxy with `@type=Resource or @type=Metadata` available?
* URL-inspection - broken links
  * in MdSelfLink
  * in ResourceProxy
  * in the CMD_elements ( less important)
* filled-in ratio / sparseness?
  - how many of the elements defined by schema are actually populated with information 
  - what about files that hardly contain any information?
  - completeness concerning relative importance 
  - coverage of the VLO facets (instance level)
* size - e.g. overall size (measured in MB)
  * is the file too big to be useful? (VLO has strong rule on max size) [[BR]]
    -> suggest higher granularity)
  * max number of !ResourceProxy per record



soft:
* values conform to a controlled vocabulary (where applicable)
* number of elements
* Length of the strings in description fields
* what is the information entropy? (lots of very similar files might be an indication of a suboptimal modelling)


problematic:
* ? publication before creation date
* ? editing quality: typos, expected format(date, capitalization, pl vs sing) 
* the combination of values in a related categorical fields is not consistent (if field A has value x, field B should have y or z)

interesting, but difficult:
* accuracy - semantic distance between data and md?
* conformance to expectation metrics?
* coherence - different metadata fields describe the same object in the same way?
* accessibility metrics - retrieval and cognitive)?
  check if you can retrieve the data, or there is login (and shib-login)
* timeliness metrics - how quality changes in time?