Metadata is information about the context, content, quality, provenance, and/or accessibility of a dataset. In order for your data to be accessible to you, your colleagues, and other researchers, it must be properly documented. Put simply, metadata is data about your data. It is:
"Data often have a longer lifespan than the research project that creates them. Researchers may continue to work on data after funding has ceased, follow-up projects may analyse or add to the data, and data may be re-used by other researchers. Well organised, well documented, preserved and shared data are invaluable to advance scientific inquiry and to increase opportunities for learning and innovation."
--"Create and Manage Data," the UK Data Archive,
Elements of metadata include:
Title - Name of the dataset or research project that produced it
Creator - Names and addresses of the organization or people who created the data
Identifier - Number used to identify the data, even if it is just an internal project reference number
Subject - Keywords or phrases describing the subject or content of the data
Funders - Organizations or agencies who funded the research
Rights - Any known intellectual property rights held for the data
Access information - Where and how your data can be accessed by other researchers
Language - Language(s) of the intellectual content of the resource, when applicable
Dates - Key dates associated with the data, including: project start and end date; release date; time period covered by the data; and other dates associated with the data lifespan, e.g., maintenance cycle updated schedule
Location - Where the data relates to a physical location, record information about its spatial coverage
Methodology - How the data were generated, including equipment or software used, experimental protocol, other things one might include in a lab notebook
Data processing - Along the way, record any information on how the data have been altered or processed
Sources - Citations to material for data derived from other sources, including details of where the source data is held and how it was accessed
List of file names - List of all data files associated with the project, with their names and file extensions (e.g. 'NWPalaceTR.WRL', 'stone.mov')
File formats - Format(s) of the data, e.g. FITS, SPSS, HTML, JPEG, and any software required to read the data
File structure - Organization of the data file(s) and the layout of the variables, when applicable
A directory of Disciplinary Metadata standards is available from the UK's Digital Curation Centre. This site is browseable by discipline. For a visualization of the wider metadata universe most often used in the humanities, see Jenn Riley's Seeing Standards. Each of the 105 standards listed here is evaluated on its strength of application to defined categories in each of four axes: community, domain, function, and purpose. The strength of a standard in a given category is determined by a mixture of its adoption in that category, its design intent, and its overall appropriateness for use in that category. The Metadata Standard Glossary provides additional description for each of the standards listed.
The Digital Library Federation has a wiki for best practices for shareable metadata. It includes general recommendations for best practices, recommendations for classes of data elements, and best practices for technical aspects of metadata.
An NSF funded project, DataONEpedia, is a database of best practices for data management. The goals are to provide a place where data can be collected, managed, and updated by appropriate individuals, and to ensure that collected data can be reused and potentially presented in multiple ways.