Geoscience Reference
In-Depth Information
originally developed to facilitate web-based publishing in a large scale, XML has since
rapidly gained acceptance and usage in the exchange of a wide variety of data on the
web. An important emerging standard for interoperability of data systems is in the
metadata area, which can use XML to share descriptions of underlying datasets.
The ability of XML to organize data into a computer-interpretable format that is
also easy to code and read by humans is quickly making XML the lingua franca for
business services and electronic commerce and also rapidly becoming a widely used
standard in the data services world. Because of its simplicity and elegance, XML has
radically transformed the provision of data services in the scientifi c community. Some
of its principal benefi ts include: (a) ability to delineate syntactic information from
semantic information; (b) allows the creation of customizable markup languages for
different use cases and application domains; (c) platform independence. For example,
XML makes it possible for providers of data services to send information about data
sets, metadata, in a form completely separate from the presentation of the underly-
ing data. Furthermore, service providers can present the same information in multiple
forms or views using XML style sheets, customized to the needs of particular users.
For example, really simple syndication (RSS) is a lightweight XML format for sharing
news and bulletins, and it has been used successfully by the US National Weather Ser-
vice to disseminate weather information such as local forecasts, watches, and warn-
ings to the Internet users. The same technology can also be used in the data services
context to notify users when new data becomes available in a data system.
Web services, based on XML and HTTP, the two open standards that have be-
come ubiquitous underpinnings of the web, are emerging as tools for creating next
generation distributed systems. Besides recognizing the heterogeneity as a fundamen-
tal ingredient, web services, independent of platform, and development environment,
can be bundled, published, shared, discovered, and invoked as needed to accomplish
specifi c tasks. Because of their building-block nature, web services can be deployed
to perform either simple, individual tasks or they can be chained to perform compli-
cated business or scientifi c processes. As a result, web services, implemented in a
service oriented architecture (SOA) or framework, are quickly becoming a technology
of choice for deploying cyberinfrastructure for data services. By wrapping existing
applications and their components as web services in a SOA, the traditional obstacles
to interfacing legacy and packaged applications with data systems are being overcome
through loosely coupled integration. Such an approach to lightweight integration af-
fords an easier pathway to interoperability amongst disparate systems and distributed
services. The new software architectures based largely on web services standards are
enabling whole new service-oriented and event-driven architectures that are challeng-
ing traditional approaches to data services. In a series of articles, Channabasavaiah et al.
(2003) present a persuasive case for developing and deploying a SOA, as the level of
complexity of traditional architectures increases and approaches the limit of their abil-
ity. They also provide a realistic plan for migrating existing applications to a SOA, one
that leverages existing assets and allows for incremental implementation and migra-
tion of those assets. Several efforts are underway within the geosciences community
to apply web services and SOAs to both migrate existing, stove-piped data systems
as well as in the development of common architectures for future data systems. For
