Wherever HASSET and ELSST share concepts, these concepts should, ideally, be identical – in labels, metadata, relationships. Everything. That said, this may not be possible every single time. The two thesauri have different cultural identities – and these will need to continue.
Following an intensive week of planning, discussion and many white board sessions, the UK Data Service team has come up with a plan to accommodate and clearly identify divergence between the two while still promoting consistency wherever possible. Rather than merging the two thesauri, HASSET and ELSST will be mapped, with the nature of these mappings made clear. Shared/core concepts will have either ‘exact equivalence’ or ‘close equivalence’. This plan is still at the drawing board stage, and so subject to change, but we expect to follow its principles in the coding of the new application.
Both SKOS and ISO-25964 support the mapping of divergence between thesauri, and we will be following these standards (and, in fact, making our system a little stricter) to show where the two thesauri match and where they do not – even if they only diverge by one word in the scope note.
A few examples of predicted divergence for ELSST and HASSET follow:
There may be cases where a definition needs to change by a single word. An example of this is the current scope note for SOCIAL ASSISTANCE. The ELSST definition refers to insurance:
“ASSISTANCE IN MONEY OR IN KIND TO PERSONS, OFTEN NOT COVERED BY SOCIAL INSURANCE, WHO LACK THE NECESSARY RESOURCES TO COVER BASIC NEEDS.”
The HASSET definition does not include this reference, because social insurance does not exist in the UK:
“ASSISTANCE IN MONEY OR KIND TO PERSONS WHOSE INCOME IS BELOW A CERTAIN LEVEL AND WHO LACK THE NECESSARY RESOURCES TO COVER BASIC NEEDS.”
Both definitions are appropriate and both are correct. They differ, however.
HASSET contains more concepts than ELSST. This is entirely expected, as HASSET holds many concepts that are specific to the UK, culturally (for example, GENERAL CERTIFICATE OF SECONDARY EDUCATION). The aim is for ELSST’s concepts to be entirely internationally applicable; however, there may be occasions when a concept that is used in 99% of European countries should still be included as it is so important to the rest of Europe. An example of this is WAGES GUARANTEE FUND, something that does not exist in the UK (or HOUSE HUSBANDS, a concept that did not exist in some other countries some time ago). To protect the integrity of the shared concepts though, structurally, these concepts must have no NTs below them which are shared between the two thesauri (as must any HASSET-only concepts).
Divergence is also required in publishing timescales. Although annual SKOS releases are made, HASSET online is constantly updated so that indexers within the UK Data Service and members of the general public may browse the current version at all times. ELSST is expected to be updated annually, following international approval of any new or changed concepts. This extra step provides a strong quality assurance measure for ELSST which ensures that all changes are internationally applicable. Divergence is required as new terms will be added to the two thesauri at different times.
Consistency is best but divergence is allowed
The principle still remains that, wherever possible, shared/core concepts should be identical; however, the system should be able to deal with areas where, for one reason or another, this just cannot happen.