<< Chapter < Page Chapter >> Page >

For researchers who perform massive simulations on distributed computing systems, portals mean Web environments that make computing resources and services accessible via Web browsers. Such portals are typically referred to as Grid portals, or science gateways. Grid portals are Web interfaces that are integrated with PC, cluster or supercomputer based computing resources. These environments very often include high level services that are not included in the underlying infrastructure, they are implemented on the portal server instead. Such services can be brokers, load balancers, data replica services, data mirroring and indexing components. All these services together with the front-end portal provide an integrated solution that enables e-scientists to deal with various aspects of data-intensive research. Usage scenarios in such portals often involve the generation and storing of research data, analysis of massive datasets, drawing scientific conclusions and sharing all these entities with colleagues or with the general public. Scientists of these portals tend to organize their frequently used steps of simulations into reusable components, called workflows. Workflows provide repeatable, traceable experiments and improve both the productivity and quality of research.

Hardware resources, software services, applications and workflows that are made accessible through Grid portals are typically provided by multiple independent organizations and are managed by different administrators. Portals connect to these distributed entities in a service oriented fashion, namely through well defined interfaces that expose the functionality of each shared component. For the sake of scalability and fault tolerance these services are accessed by the portal through some catalogues. A typical difficulty of portal design is how to integrate the content from the dynamic services of the catalog into a user friendly view that is ergonomic, provides coherent information, and at the same time flexible and easily customizable for different user preferences.

In the early years of Grid computing the portal systems were implemented using various different programming approaches and languages. Despite Grid solutions have much simplified since those early years, developers of science gateways must still know relatively high number of technologies. Portal operators must closely follow the evolution of Grid middleware services, because updates on the portal are required when the Grid middleware is changed. While enterprise portals also demand regular updates due to changes in the back-end systems, the technological evolution in Grid computing is more rapid than in business environments. As grid portals shield users away from middleware evolution, they are very often the only way for scientists to stay connected with Grids over longer period of time.

There are a few other technical difficulties that are specific to Grid portals. The issue of how to map the security model of Grid systems to the security model of the “Web” is one of these. While Web portals identify and authenticate users with account-password pairs, Grids and other sorts of distributed computing environments use certificates. Certificates enable users to authenticate only once in a distributed system and perform complex operations without being asked for account details over and over again (e.g. in every stage of the orchestration of a workflow). By certificates the users can delegate their access rights to workflow managers, brokers, catalogs and other services that perform activities on their behalf. Grid portals typically translate username-password pairs to certificates by either through certificate repositories (such as MyProxy), or by importing certificates from Web browsers.

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Research in a connected world. OpenStax CNX. Nov 22, 2009 Download for free at http://cnx.org/content/col10677/1.12
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Research in a connected world' conversation and receive update notifications?

Ask