Put simply, metadata is "data about data". It enables effective, efficient, and accurate use of datasets and data collections, and is the departure point for all discovery systems. In paper-based systems, the card catalogues contain the metadata; in the current digital world, machine-readable repositories contain the metadata. It allows for precise description of resources and the sharing of these descriptions as individual containers, called metadata records, without the necessity of involving the resources themselves in the transaction.[5]
Metadata holds different meanings for different people. To metadata creators, it is a means of moving data from an unorganized pool of resources to an organized pool. Creating metadata helps us to organize knowledge about a given domain and present it at a higher level of abstraction, so that it can be more easily maintained at both the dataset as well as the collection level. To system designers, metadata represents an efficient medium allowing for fast access to resources, especially when resources are "non-searchable" such as images, videos, power point files, audio/sound files. Finally, for users, metadata is a quick way of accessing information without having to go through each resource one by one. Imagine, for example, a library without a card-catalogue with the title, author or subject information about the available books and journals. The only way to find the book that you are interested in would be by looking at every book on the shelf!
The AgMES project was launched in November 2000, at a workshop in Brussels jointly organized by FAO and OneWorld Europe.[6] The aim of the project is to promote, among other things, the use of metadata through the adoption of standardized agricultural metadata terms, to "simplify resource discovery and interoperability between and among uniquely and richly described agricultural resources".[7] The project intends to promote the integration of data from different sources, and to engage in - and thus demonstrate the benefits of - effective data exchange. The AgMES metadata defines elements, qualifiers, encoding schemes and controlled lists that are generic, yet necessary, to describe agricultural resources such as projects, presentations, images, best practices, statistical data, maps etc., in all areas relevant to food production, nutrition and rural development. Initial work concentrated on the description of document-like resources, e.g. maps, audio files, images, webpages, books, journals, journal articles, PowerPoint presentations etc.
The primary goal of the AgMES project was to define an interoperability layer, using emerging standards, that facilitates the efficient exchange and use of agricultural content, allowing national agricultural databases and FAO to efficiently exchange information. This means that local databases could be part of the "open exchange of information" scene, without requiring them to change anything in the database itself. This method promotes the mapping of local database structures to a commonly accepted data model and the use of metadata harvesting protocol defined by the Open Archives Initiative (OAI) to harvest this metadata, contained within XML files, for reuse.[8] The OAI promotes heightened "access to e-print archives as a means of increasing the availability of scholarly communication".[9] A simple Dublin Core (DC) format, consisting of the 15 unrefined elements functions as a common denominator to homogenize both harvested raw data or sets of results produced by parallel searching on distributed databases.[10]
The 15 Dublin Core elements and their refinements and schemes were not sufficient to describe agricultural resources. Therefore, we decided to extend this element set with necessary agriculture specific elements, refinements and schemes. Here are brief descriptions of what each of these is:
Element - refers to a label that describes particular information about a resource, e.g. Title, Creator, Date.
Refinement - makes the meaning of an element narrower or more precise, e.g. the element subject is made specific by dividing it into subject as defined by a classification scheme and a subject as defined by a thesaurus.
Scheme - aids in the interpretation of the value of an element, e.g. the use of YYYY-MM-DD as a format for encoding dates of a resource. Schemes are usually controlled vocabularies, controlled lists, and formal notations or parsing rules that allow for further understanding of the content of an element.
The steps involved in defining these new extensions to DC elements included:
developing a conceptual framework of different types of document-like agricultural information resources to homogenize the description of meta elements;
evaluating other available standards and common resource description practices to avoid reinvention of the wheel;
identifying 13 core elements for resource description at generic level and qualification of elements (using the DC guidelines), to enable description of resources at different levels of granularity;
preparing draft specifications of new elements, refinements and schemes;
discussing these proposals within the agricultural community, mainly through the AgStandards discussion forum.
AgMES encourages the exchange of metadata in a platform-independent yet machine-readable format (such as XML). Let's look at an example of how content, or parts of a metadata record, can be tagged in XML. Imagine we have a resource called, "Review of ocean climate research on the role of the Nordic countries in global ocean climate research". This review article can be described with the following subject keywords: Climatology, Oceanology, and Hydrological Cycle. The first example below shows the "subj" tag being used to encode the above three keywords in XML. The second example uses the tag called "dc: subject" from the DC metadata element set. The tag is further refined with "ags:subjectThesaurus", using the refinements made in the AgMES Project. The tag can be further qualified with an attribute "scheme" to allow us to specify that these three subject keywords were taken from FAO's multilingual AGROVOC Thesaurus.[11] Table 1: XML encoding
The goal of the AgMES project is to define intelligently tags, or element names, such as "ags:subjectThesaurus", and propose correct schemes to allow us to know more about the content of these elements.[12] Furthermore, using schemes or controlled vocabularies like AGROVOC helps us to control the source of the content and to maintain a level of quality. The elements defined by the AgMES supplement the DC elements. They may be used not only together with DC but also with other metadata standards. This property of metadata allows for easy manipulation and customization of metadata to suit the specific needs of a given application.
Future developments and documentation to support the project will include:
developing good documentation and user guidelines;
monitoring the impact of the proposed metadata for agricultural resources, making any changes or improvements based on the results of the impact study;
registering the new metadata elements in established registries to promote its expansion and uptake;
launching pilot projects between FAO and agricultural subject gateways to share metadata about agricultural resources in a commonly accepted XML based format;
creating a metadata clearinghouse for exchange of knowledge and advances on semantic standards in the domain of agriculture.
