his standard is more widely adopted, the ALA will support and promote it as a preferred data model.
It should be noted that Darwin Core, ABCD and the TaxonOccurrence vocabulary are all designed to handle the exchange of “presence” data, i.e. data sets which comprise records of the actual occurrence of different species. These data standards are inadequate to represent the full complexity of many ecological data sets. In particular they lack any standard mechanism for expressing level and standardisation of recording effort or for recording the absence of a species of interest. The TDWG Observation and Specimen Records Interest Group is exploring ways to represent this further level of information, and the ALA will participate in this process. In the mean time, the ALA encourages data providers to use one of these existing standards to share their data and to provide a text description of any underlying data collection methods in the metadata for the data set.
Some data sets (particularly ecological data sets) will include data elements for which there is no corresponding property in Darwin Core or in the TaxonOccurrence vocabulary. In such cases data providers are recommended to use appropriate terms from other vocabularies to label these additional elements (see for example the range of vocabularies and ontologies listed by Marine Metadata Interoperability or SPIRE). If these elements are of general importance to biodiversity projects, it is also recommended to initiate discussion with TDWG to make standard recommendations on their representation.
Taxonomic and nomenclatural data is frequently much more complex than species occurrence data, with many nested relationships between data items. Different data sets contain different combinations of nomenclatural data (information on the origin and validity of scientific names), taxonomic data (judgments on which names correspond to real species, how these species are to be classified and how they relate to earlier names and species concepts), bibliographic data (details of nomenclatural and taxonomic literature) and often a range of legislative, distributional and other information.
In addition, the hierarchical nature of classifications and checklists is handled in different ways in different databases. Some databases have a single table to accommodate taxa of all ranks, and rely on parent-child relationships and explicit taxon rank elements. Others flatten the hierarchy and assign different ranks to different database columns. There is similar variation in the way that different databases model the relationships between the names each database accepts for a species and the various synonyms identified in the database for the same species.
All of this makes it hard to provide generic recommendations for sharing data of this kind. To simplify the problem slightly, we can distinguish data sets according to their primary purpose:
There are several relevant data standards which have been used to share such data. The ALA will seek to support data shared using any of the following models:
Nomenclatural and taxonomic databases can be exposed as a TCS document (accessed via a Plain URL) or as a set of smaller TCS documents each representing a single taxon name or taxon concept (and accessed via a TAPIR search interface). It is however preferable in such cases to use the TaxonName and TaxonConcept vocabularies and to use LSIDs (and perhaps also OAI-PMH) in addition to, or instead of TAPIR.
For other data sets, it will often be more appropriate simply to share the entire data set as a single document in a tab-delimited or comma-separated format, with terms from the TaxonName and/or TaxonConcept vocabularies or the SPICE Common Data Model as column headings and explanation of the purpose of the list included as part of the metadata for the data set. This approach may be applicable for listing protected species (red lists, CITES, etc.), species exhibiting some characteristic (e.g. endemic, invasive, venomous or leaf-mining taxa) or checklists for protected areas or localities.
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