News

ArcUser Online


Search ArcUser

 

E-mail to a Friend

Expanding Data Sharing with Metadata Services
By Margaret Lyszkiewicz, Esri ArcIMS Team

click to see enlargement
The Metadata Explorer is a Web-based JSP application designed for searching a metadata server.

The ArcIMS Metadata Services, a core component of ArcIMS 4, let users create customized and centralized online repositories of metadata at any level--Intranet, Extranet, or Internet.

Metadata Services are built on the functionality of three existing Esri products--ArcIMS; ArcCatalog, one of the ArcGIS applications; and ArcSDE. A perfect example of merging technologies, Metadata Services use ArcIMS for framework and architecture; ArcCatalog for creating, authoring, and publishing metadata; and ArcSDE as the interface to the relational database that stores published documents. Metadata stored in a metadata server is accessed using either ArcCatalog or Metadata Explorer, a Web-based tool.

Building Global Communities

The Metadata Services expand Esri's vision of global data sharing by making it easier to document and locate datasets. Data producers now have a place to publish data, and data consumers have a place to find data. Although only metadata--a document that describes data--is published to the server, access to the data itself can be provided by including direct links to the online sites containing data, contact information, or the storage locations for data in the metadata document.

Customizable, Interoperable, and Internationalized

Metadata authored in ArcCatalog is stored and published to the Metadata Server in extensible markup language (XML) format. XML is a metamarkup language, but unlike HTML, it describes structured data content rather than display properties. A swiftly emerging open industry standard that is platform neutral and oriented to publishing and distributing information using the Internet, XML's characteristics help make Metadata Services open, standard-independent, and international.

Any metadata published in valid XML will be accepted by a metadata server. The semantics of the published documents are handled by client applications that can easily be customized to match any data standard, foreign language, or custom content. Metadata Services are available on any platform supported by ArcIMS (Windows, Solaris, Linux, AIX, HP-UX) and on top of any relational database supported by ArcSDE (SQL Server, Oracle, Informix, DB2).

Supporting Standards

Although Metadata Services do not conform to one single standard, they do comply with the specifications of the Open Geospatial Consortium, Inc. (OGC). An international industry consortium of more than 220 companies, government agencies, and universities, OGC is developing publicly available geoprocessing specifications. Open interfaces and protocols defined by OpenGIS specifications support interoperable solutions for "geo-enabling" the Web; wireless, location-based services; and mainstream IT applications. More information on OGC is available from www.opengis.org.

Metadata Services diagram

Built on the functionality of three existing Esri products--ArcIMS; ArcCatalog, one of the ArcGIS applications; and ArcSDE--Metadata Services are a perfect example of merging technologies.

The OpenGIS Abstract Specification describes the OGC's view of metadata in a series of 11 scenarios. The following list of excerpts shows how Metadata Services support each scenario included in the OpenGIS Abstract Specification.

Scenario 1: "Searching for feature collections using metadata element names and their associated values."

Both search clients--ArcCatalog and the Metadata Explorer--can search for the values of specific metadata elements. This capability is available through the interface and is also fully customizable.

Scenario 2: "Posting metadata about a dataset so that it might be discovered by a potential user."

ArcCatalog, the publishing client for Metadata Services, can publish metadata for any dataset to the online server.

Continued on page 2

Contact Us | Privacy | Legal | Site Map