A considerable amount of work in relation to standards for spatial data has taken place at an international level. The International Organisation for Standardisation (ISO) has a technical committee (TC 211) which has focused exclusively on this type of information. The Committee is overseeing the development of over 40 separate spatial data related standards. Some of these standards have been adopted by the ISO and others are in various stages of development or approval.
The Open GIS Consortium (OGC), in conjunction with ISO, has produced a variety of data interoperability standards relating to spatial data.
The Committée Européen de Normalisation (CEN) is the European body responsible for standards. When CEN adopts standards they become mandatory on Member States. CEN will probably consider ISO and Open GIS Consortium standards and adopt them with possible variations to suite European conditions.
The National Standards Authority of Ireland (NSAI) is responsible for representing Ireland's views on developing European and international standards, and for implementing them as national standards.
eGovernment initiatives across Europe (and beyond) are also defining standard elements of services and data, many of which inevitably include spatial information.
More generally, the Open Source software model of development promotes standardisation in addition to dealing with other important aspects such as portability, sustainability, and flexibility
Some key areas for standardisation from the point of view of the ISDI are set out below.
Catalogue . A catalogue is the system that enables spatial data to be organised, discovered and accessed. Catalogues have been described as being 'at the heart of any SDI'.
 It is thus important that catalogues can be easily and unambiguously accessed by all users using various software tools.
Metadata . Metadata is 'data about data' and describes the contents, structure, format and lineage of data sets. Again, easy and unambiguous access to this information is vital for an SDI. The key standards in this case are probably Dublin Core
 which would provide a high level set of information about spatial data set contents and the ISO Standard 19115
 which provides for considerably more detail regarding a dataset.
Gazetteer . A gazetteer is a listing of information in a standard format, for instance of postal addresses, street names or locality names. The necessary format needs to be standardised to ensure that definitive information is accessed.
Georeferencing system . A coordinate reference system is a fundamental basis of all spatial data. It is therefore vital that the system(s) in use are clearly defined and there are definitive means of moving between them. Relevant systems for an ISDI probably include the Irish Transverse Mercator (ITM) which has been adopted by Ordnance Survey Ireland as the basis for its mapping, Universal Transverse Mercator (UTM) for international applications, and a sea level (height) reference system.
Interoperability standards including data transfer language . It is vital that data can be exchanged between systems in a way which does not lose, alter or corrupt information. To support this, OGC and ISO TC211 are documenting and standardising the Geography Markup Language (GML)
 which is a form of Extensible Markup Language (XML
). GML is the likely future standard for the encoding and transport (e.g., over the Internet) of spatial data.
Software . It will be vital to ensure that organisations using different software systems can share data between themselves. The OGC has undertaken a considerable amount of work in this area, including a programme of verification that various software systems meet interoperability requirements. Many organisations, however, are using systems which have been developed many years ago, or for their own particular purposes. Such systems many not meet the latest interoperability standards.
eServices. The OGC is currently working in this area and there may be an EU Directive dealing with services at some point in the future.
Semantic interoperability. Terminological confusion can create substantial difficulties. It may be that clarity in this regard will be introduced through the EU's eGovernment Directive (refer to the EU IDA web site).
Data quality standards. It is vital that we all understand each other when discussing the 'quality' of a dataset, to ensure that the most appropriate dataset is used for each particular purpose, particularly in cases where differing datasets exist. This requires clear definition of quality measures, and consistent use of terminology.
In all of these cases, we will need to consider what use Ireland makes of official standards and where we choose to develop standard specifications that focus particularly on Ireland's needs.
INSPIRE Architecture and Standards Position Paper, October 2002. (see
GML is an XML-based language for encoding and transport of geographic information. See