N. Manouselis, C.Costopoulou, A. Sideridis, “Metadata for Web Portals: Developing an e-Markets’ Directory”, accepted for publication in A. Tatnall (Ed.), "The Encyclopedia of Portal Technology and Applications", Hershey, PA: Idea Group Publishing, 2007.
Metadata for Web Portals: Developing an e-Markets’ Directory Nikos Manouselis, Constantina Costopoulou, Alexander B. Sideridis Informatics Laboratory Division of Informatics, Mathematics & Statistics Dept. of Science, Agricultural University of Athens, Greece {nikosm,tina,as}@aua.gr Abstract. Metadata (that is, data about data), may greatly facilitate content collection, description, categorisation, location, and retrieval in the context of Web portals. It can be used to support the development of Web portal services that are based on the collection of content objects (resources). In this article, we present how metadata can be used to support the development of a particular case of Web portal service, an e-markets’ directory service. First, the concept of metadata is introduced and related notions are explained. Then, the case of a Web portal for Organic Agriculture (OA) is introduced. The content categories of this portal are presented, and the development of appropriate metadata for the description and categorisation of the content sub-category of OA e-markets is described. A prototype implementation of an e-market directory service is also introduced. The presented case study is expected to provide useful insight into the use of metadata for researchers, managers and developers of Web portals. Keywords: Metadata, directory service, e-markets, organic agriculture.
1. Introduction Web portals can be defined as gateways to information and services from multiple sources (Tatnall, 2005). An important aspect of Web portals is the organisation, navigation, labelling and indexing of their content in order to facilitate searching of information and services (that is, the Web portal content). One of the aims of Web portals is to collect and categorize content objects (otherwise called resources), so that users can search, identify and access the most appropriate resources for their needs. Metadata play a critical role in such systems. Metadata is defined as structured information that describes, explains, locates, or otherwise makes it easier to retrieve, use, or manage a resource. It is often called ‘data about data’ or ‘information about information’ (NISO, 2004; Steinacker et al., 2001). Web metadata is used to provide information about resources which do not necessarily need to be displayed on the screen. It can then be used by software such as search engines or content management systems. Examples of information commonly stored as metadata include authorship, publication date, modification date, copyright information, and subject keywords. Metadata can be therefore used in the context of Web portals to describe resources, and thus to facilitate their categorization, storage, search and retrieval procedures (Miller, 1996; Duval et al., 2002). In this article, we provide an overview of what metadata is, and how it can be used for the description, categorization and classification of Web portal content. Using the case study of an Organic Agriculture (OA) Web portal, the appropriate metadata for describing OA e-markets and developing an e-market directory service is defined.
2. Background Metadata is made up of data items that can be added to or attached to a resource. Such data items can be (i) machine-readable, giving software applications the data they need to interpret the information held on a resource, or (ii) designed for human interaction, listing the creator,
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N. Manouselis, C.Costopoulou, A. Sideridis, “Metadata for Web Portals: Developing an e-Markets’ Directory”, accepted for publication in A. Tatnall (Ed.), "The Encyclopedia of Portal Technology and Applications", Hershey, PA: Idea Group Publishing, 2007.
subject, title, and other data needed to find and manage the resource. These data items are better known as metadata elements. Three types of metadata elements have been identified (NISO, 2004): • • •
Descriptive metadata elements, which describe a resource for purposes such as discovery and identification. They can include elements such as title, abstract, author, and keywords. Structural metadata elements, which indicate how compound objects are put together. For example, how pages are ordered to form chapters. Administrative metadata elements, which provide information to help manage a resource, such as when and how it was created, file type and other technical information, and who can access it. There are several subsets of administrative metadata elements, such as: o Rights management metadata elements, which deal with intellectual property rights. o Preservation metadata elements, which contain information needed to archive and preserve a resource.
Metadata can be embedded in a resource or can be stored separately (NISO, 2004). More specifically, the following ways of associating metadata with resources have been identified (Duval et al., 2002): embedded metadata resides within the resource; associative metadata is maintained in files tightly coupled to the resource it describes; and third-party metadata is maintained in a separate database (termed as a metadata repository) by an organization that may or may not have direct control over or access to the content of the resource. To use and benefit from metadata on the Internet, we need a common format for expressing it that should be designed for machines rather than humans (Steinacker et al., 2001). Metadata schemas (or metadata models) are sets of metadata elements designed for a specific purpose, such as describing a particular type of resource (NISO, 2004). The definition or meaning of the elements themselves is known as the semantics of the schema. The values given to metadata elements are the content. Metadata schemas generally specify names of elements and their semantics. Optionally, they may specify content rules for how content must be formulated (for example, how to identify the main title), representation rules for content (for example, capitalization rules), and allowable content rules (for example, terms must be used from a specified controlled vocabulary). There may be also syntax rules for how the elements and their content should be encoded. A metadata schema with no prescribed syntax rules is called syntax-independent. Metadata specifications are well-defined and widely agreed metadata schemas that are expected to be adopted by the majority of implementers in a particular domain or industry. When a specification is widely recognized and adopted by some standardization organization (such as ISO), it then becomes a metadata standard. There is no one all-encompassing metadata standard to be used in all applications. Rather, there are various metadata standards or specifications that can be adapted or ‘profiled’ to meet community context-specific needs (Kraan, 2003). This conclusion has lead to the emergence of the application profile concept. An application profile is an assemblage of metadata elements selected from one or more metadata schemas, and the purpose of an application profile is to adapt or combine existing standards or specifications into a package that is tailored to the functional requirements of a particular application, while retaining interoperability with the original base schemas (Duval et al., 2002).
3. Using metadata for the Bio@gro Web portal The Bio@gro Web portal provides online access to accurate and multilingual OA information and resources, as well as to mobile services for all actors involved in the OA value chain (e.g.
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N. Manouselis, C.Costopoulou, A. Sideridis, “Metadata for Web Portals: Developing an e-Markets’ Directory”, accepted for publication in A. Tatnall (Ed.), "The Encyclopedia of Portal Technology and Applications", Hershey, PA: Idea Group Publishing, 2007.
organic farmers, distributors, retailers, food companies, agribusinesses, consumers). This Web portal is being developed in the context of the European e-Content Programme project 11293 ‘Bio@gro’ for information dissemination and public awareness increase regarding OA (http://bioagro.aua.gr). The Bio@gro project is being implemented by a cross-European consortium, including nine partners from four European countries. The portal is currently under development, and it is expected to be launched in full operation by the end of 2006. Metadata is used in the context of the Bio@gro portal to describe the OA-related resources which are described and categorized in the portal databases. This metadata is being authored and maintained by the Bio@gro portal team. It is stored in a specially designed metadata repository, separately from the actual resources. Therefore, Bio@gro is engaging a third-party metadata storage approach. The main uses of the metadata descriptions in the portal are for descriptive and for administrative purposes, therefore corresponding metadata elements have been defined for each resource category. These elements have been adopted and specialized from existing metadata schemas, so that to facilitate both the reusability (e.g. in other Web portals) and the interoperability (e.g. with other database systems) of the resources’ descriptions. Thus, the metadata schemas to be used in Bio@gro are application profiles of existing metadata schemas. 3.1 Bio@gro Content Objects The OA resources intended to be included in the Bio@gro portal are distinguished in several content categories, and consist of what are termed as ‘Bio@gro Content Objects’ or simply BCOs. A BCO is a single information unit that can be identified, collected, and described for the Bio@gro portal in a meaningful and useful (for the OA actors) way. The format of a BCO can be digital or non-digital. BCOs in a digital format are expected to be categorized in the portal, either collected from the Web or developed by Bio@gro. Other types of BCOs may be non-digital ones, including traditional information resources, such as books or articles in printed media like magazines or scientific journals. For non-digital BCOs, only their description will be provided in the Bio@gro Web portal. BCOs may also have related copyrights or permissions of use: some maybe freely uploaded in the Bio@gro portal (no permission rights), and some may not (restrictive copyrights or permissions of use). For the latter ones, again only a description will be included in the portal. Interested users will have to access copyrighted BCOs according to the policy of the copyright holder, e.g. through the Web site of the publishing house for a scientific paper. The major content categories are OA information resources (such as news, events, reports, and other documents), educational resources (such as online courses, best practice guides, and educational videos on OA topics), e-government resources (such as online addresses of governmental organizations dealing with OA and Web sites of OA agencies), and e-markets with OA products and supplies. Each content category requires the use of a particular metadata schema, to reflect the special properties of each type of BCOs. In Bio@gro, four different metadata schemas are being used for the description and classification of the BCOs. These metadata schemas are the Dublin Core standard (DC, 2004), the IEEE Learning Object Metadata (IEEE LOM, 2002), the e-Government Metadata Standard (e-GMS, 2004), and the Dublin Core for E-Markets (DC-EM) metadata schema (Manouselis & Costopoulou, in press). Each one of these metadata schemas has been specialized in order to become appropriate for the needs of the Bio@gro portal, creating four corresponding Bio@gro application profiles. 3.2 Examined Case Study An important category of BCOs are electronic markets (e-markets) with OA products. Through a directory service of OA e-markets, OA actors with e-markets will be able e.g. to
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N. Manouselis, C.Costopoulou, A. Sideridis, “Metadata for Web Portals: Developing an e-Markets’ Directory”, accepted for publication in A. Tatnall (Ed.), "The Encyclopedia of Portal Technology and Applications", Hershey, PA: Idea Group Publishing, 2007.
promote their products and services to distributors and suppliers, or consumers will be able to locate online e-markets with OA products. Various types of e-markets can be identified, including electronic storefronts, e-shops, emalls, online auctions, online exchanges etc. (Turban et al., 2004). From a general point of view, three major categories of agricultural e-markets have been identified (Wilson, 2001): emarkets for the outputs of farms, e-markets for the production factors and inputs of farms (e.g. machinery parts, seed, chemicals), and e-markets of services by third parties, which offer specialised support services to farmers (e.g. logistic, transport, banking, insurance and legal services). Numerous e-markets of the agricultural sector are currently operating online (Manouselis et al., 2005), including many offering OA products. In order to describe the particular characteristics of these e-markets, a specialised metadata schema has been developed, which has been based on the DC-EM (Manouselis & Costopoulou, in press). For the needs of the Bio@gro Web portal, a Bio@gro DC-EM application profile for e-markets has been created. An overview of its elements is provided in Figure 1. Table 1 illustrates the use of the proposed application profile for the example of the GreenTrade.net e-market.
Figure 1: An overview of the elements of the Bio@gro application profile for e-markets.
ELEMENT Identifier Title Description Source Publisher Name Address Country Telephone E-mail Type emTransactionPhase emFlow
VALUES EMID0025 GREENTRADE.NET Electronic marketplace that aims to contribute to the development of organic agriculture and make it possible to sell, export, communicate and gather information effectively as cheaply as possible. http://www.greentrade.net GreenTrade 8 rue du Professeur Roux, 92370, CHAVILLE FRANCE + 33 1 47 50 02 73
[email protected] Information, Negotiation, Settlement B2B
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N. Manouselis, C.Costopoulou, A. Sideridis, “Metadata for Web Portals: Developing an e-Markets’ Directory”, accepted for publication in A. Tatnall (Ed.), "The Encyclopedia of Portal Technology and Applications", Hershey, PA: Idea Group Publishing, 2007. Internet English, French, Spanish International
Medium Language Coverage Rights accessRights
Private
Subject Organic Agriculture in general
Keyword Products/Services
Organic fertilizers and plant nutrients; Food Beverage and Tobacco Products; Chocolate and sugars and sweeteners and confectionary products; Herbs and spices and extracts Consumers/Citizens
Audience Meta-Metadata Contribute Role Creator Entity Nikos Manouselis Date 2001-08-23 BIOAGRO DC-EM Application Profile Metadata Schema en Language Table 1: Example of using the Bio@gro application profile for describing an OA e-market.
Figure 2: A screenshot of the prototype of an e-market directory service.
Using this application profile, the Bio@gro portal team is creating a collection of OA emarket descriptions, which will serve as the basis of a directory service of e-markets with OA products for the Bio@gro Web portal. An example of how this directory service can be implemented is presented through the e-Market Metadata (eMaM) directory service prototype (Manouselis & Costopoulou, 2005), which is available online at: http://eservices.aua.gr/eMaM.htm. This prototype of the directory service demonstrates how a
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N. Manouselis, C.Costopoulou, A. Sideridis, “Metadata for Web Portals: Developing an e-Markets’ Directory”, accepted for publication in A. Tatnall (Ed.), "The Encyclopedia of Portal Technology and Applications", Hershey, PA: Idea Group Publishing, 2007.
metadata repository with e-market descriptions may offer a variety of searching and browsing facilities to the users searching for an appropriate e-market. A screenshot of the eMaM prototype is presented in Figure 2.
4. Future Trends The use of metadata is currently considered a key enabler for all applications areas in the World Wide Web. In the context of Web portals, metadata is expected to support a wide variety of tasks, including the following (NISO, 2004): • • •
•
•
Resource discovery: discovery of relevant information by allowing resources to be found using relevant criteria, identifying resources, bringing similar resources together, distinguishing similar resources, and giving location information. Organising online resources: useful in aggregating and organizing links to resources with similar characteristics, using metadata stored in online databases called metadata repositories. Interoperability: describing a resource with metadata allows it to be understood by both humans and machines in ways that promote interoperability. This refers to the use of predefined metadata, shared transfer protocols, and crosswalks between schemas, so that resources from different portals across the Internet can be searched more effectively and seamlessly. Digital identification: many metadata elements represent standard numbers to uniquely identify the object to which the metadata refers. This is related to the unique identification of a digital object in the World Wide Web, using a file name, URL (Unified Resource Locator), or some more persistent identifier such as a PURL (Persistent URL) or DOI (Digital Object Identifier). Archiving and preservation: there is a growing concern that online resources will not survive in a usable form in the future, since online information is fragile, it can be corrupted or altered, intentionally or unintentionally. This requires special metadata to track the lineage of a content object (where it came form and how it has changed over time), to detail its physical characteristics, and to document its behavior in order to emulate it on future technologies.
5. Conclusions In this article, the concept of metadata is introduced, and related notions are described. In addition, the case of the Bio@gro Web portal for the OA sector is examined. Focus is given on the content categories of Bio@gro portal, which include an OA e-markets directory service. To facilitate the development of this directory service, an application profile for emarkets is developed. This article provides both an overview of what metadata is, as well as, how it can be used for the description, categorization and classification of Web portal content objects. It also illustrates a case study of how metadata is used in the context of a particular portal service. Therefore, it is expected to be of added value for researchers, managers and developers of Web portals that aim to deploy metadata-based services.
6. Acknowledgement The work presented in this paper has been partially funded by the European Commission, and more specifically the e-Content project No EDC-11293 ‘Bio@gro’. The authors of the paper
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N. Manouselis, C.Costopoulou, A. Sideridis, “Metadata for Web Portals: Developing an e-Markets’ Directory”, accepted for publication in A. Tatnall (Ed.), "The Encyclopedia of Portal Technology and Applications", Hershey, PA: Idea Group Publishing, 2007.
would like to thank project partners for their assistance in the definition of the application profile.
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