Controlled Vocabularies Providing context Controlled Vocabularies Sean Gaffney (with acknowledgements to Rob Thomas, BODC)

What is a vocabulary? A person's vocabulary is the set of words within a language that are familiar to that person. A vocabulary usually develops with age, and serves as a useful and fundamental tool for communication and acquiring knowledge. (R. Thomas, BODC, September 2016)

Why use controlled vocabs? Divided by a common language (R. Thomas, BODC, September 2016)

Why use controlled vocabs? Support terms with explicit definitions Remove ambiguity Resource for all Publish on the web Make the implicit become explicit! (R. Thomas, BODC, September 2016)

MEDIN & Controlled Vocabs Where do MEDIN use controlled vocabs? Data Guidelines and Discovery Metadata Standard How to access the MEDIN vocabularies?

Availability through website www.oceannet.org

Vocabularies used by MEDIN http://www.epsg.org/ http://www.marinespecies.org/msbias/index.php http://www.ices.dk/datacentre/reco/

NVS2 Vocab Service: Hosted at BODC. Manual search link is: https://www.bodc.ac.uk/data/codes_and_formats/vocabulary_search/ Uses Simple Knowledge Organization System (SKOS) concepts to build URLs: Format is: http://vocab.nerc.ac.uk/collection/collectionID/collectionVersion/status/ Example: http://vocab.nerc.ac.uk/collection/P02/current/accepted/ Fully computer readable. Output in XML

NVS2 Vocabulary client https://www.bodc.ac.uk/data/codes_and_formats/vocabulary_search/ Instruments, platforms, sea areas, geometries etc

Relationships between vocabs

MEDIN Keywords Keywords describe certain aspects of your dataset MEDIN recommends “SeaDataNet Parameter Discovery Vocabulary” – P02 Accessible through NVS2 and SeaDataNet Two SeaDataNet routes Access table P02 directly from MEDIN website Use SeaDataNet hierarchy to do this P01 route through NVS2

SeaDataNet hierarchies Parameter relationships and discovery How best to choose your P02 term?

P01 route through NVS2

This gives you term for measurement

Things to be aware of… Links on MEDIN vocab page bring you to SeaDataNet vocab list page, not to individual vocabs or NVS2. Searching may not be intuitive – definitions may have text in different orders to what is expected e.g. sea temperature as ‘Temperature of the water column’ not ‘Water column temperature’ Vocabs are no use if not correctly referenced…what is best practice? URIs, term codes, vocabulary full titles, dates etc. Different vocabs may have similar terms but different use cases. Research which is the right one for your needs. Unusual terminology

How to add? E-mail Sean Gaffney sgaf@bodc.ac.uk - check with appropriate governance group.

Providing context - Coordinate Reference Systems The data were sampled at 252 345.9, 204 301.6 The data came from an area 6 miles from the lighthouse, bearing 245 degrees Data cost money to sample. Without knowing where and when a measurement or observation occurs they have no value. Need therefore to be able to provide a trustworthy unambiguous position for samples. Are the following numbers enough to provide precise positions of sampled data? The data are from 54 degrees 10’ 45’’ North, 3 degrees 30’ 20’’ West

Coordinate Reference Systems LATITUDE and LONGITUDE are NOT UNIQUE! Coordinates define a position unambiguously only when the reference system that those coordinates are part of has been identified!

Coordinate Reference Systems What is a CRS? This is a coordinate system which is referenced to the earth based on a datum. OGP, 2007, Surveying and Positioning Guidance note 1

Coordinate Reference Systems Where is the Eiffel Tower? Coordinates: 48°51’29’’N, 2°17’40’’E OGP, 2007, Surveying and Positioning Guidance note 1

Implications! Platform drilling . Meridional grid wrongly applied in directional software. 12 dry wells dug. Loss of capital expenditure of $2 million. Reputation damage. New program of work needed Construction. Proposed position for new subsea manifold issued on ED50 datum. Contractor assumed positions in WGS-84 and drilled in wrong place. Resulted in fine of $500,000, reputational damage and contract dispute between contract parties

Practice Aim – to familiarise yourself with different controlled vocabularies Navigate to the MEDIN webpage for controlled vocabularies within www.oceannet.org 2) Try and locate some suitable MEDIN keywords from P02 using The NVS 2 service The link to table P02 in the SeaDataNet List The P08/theme approach from SeaDataNet d) Using P01, trying wildcards to see how they are handled in the system 3) How would you reference these keywords? 4) What other vocabularies and terms are of use to your work? 5) Have a search of the EPSG registry and note your impressions – what would you give as a reference for a particular CRS?