Grid

Grid Computing is an emerging computing model that treats all resources as a collection of manageable entities with common interfaces to such functionality as lifetime management, discoverable properties and accessibility via open protocols. Today resource allocation in a grid is increasingly done in accordance with SLAs (service level agreements).

The semantic web is an evolving extension of the Web in which web content can be expressed not only in natural language, but also in a form that can be understood, interpreted and used by software agents, thus permitting them to find, share and integrate information more easily. It derives from W3C director Tim Berners-Lee's vision of the Web as a universal medium for data, information, and knowledge exchange.

At its core, the semantic web comprises a philosophy, a set of design principles, collaborative working groups, and a variety of enabling technologies. Some elements of the semantic web are expressed as prospective future possibilities that have yet to be implemented or realized. Other elements of the semantic web are expressed in formal specifications. Some of these include RDF, a variety of data interchange formats (e.g RDF/XML, N3, Turtle, N-Triples), and notations such as RDFS and the OWL -- all of which are intended to formally describe concepts, terms, and relationships within a given knowledge domain.

RDF

Resource Description Framework (RDF) is a family of W3C specifications originally designed as a metadata model but which has come to be used as a general method of modeling information, through a variety of syntax formats.

The RDF metadata model is based upon the idea of making statements about resources in the form of subject-predicate-object expressions, called triples in RDF terminology. The subject denotes the resource, and the predicate denotes traits or aspects of the resource and expresses a relationship between the subject and the object. For example, one way to represent the notion "The sky has the color blue" in RDF is as a triple of specially formatted strings: a subject denoting "the sky", a predicate denoting "has the color", and an object denoting "blue".

This mechanism for describing resources is a major component in what is proposed by the W3C's Semantic Web activity: an evolutionary stage of the Web in which automated software can store, exchange, and use machine-readable information distributed throughout the web, in turn enabling users to deal with the information with greater efficiency and certainty. RDF's simple data model and ability to model disparate, abstract concepts has also led to its increasing use in knowledge management applications unrelated to Semantic Web activity.

• Getting into RDF & Semantic Web using N3

TripleSpace (Semantic TupleSpace)

The web and the tuplespace have many things in common. They are both global information spaces for persistent publication. Therefore, they share many of their underlying principles. They differ in their application context. The web is a world wide information space for the human reader and the tuplespace is a local space for parallel computation. We propose to extend the tuplespace into a triple-space, where <subject, predicate, object> describe content and semantics of information. The object can become a subject in a new triple and so defining a graph structure capturing structural information.

- Dieter Fensel, Tim Berners-Lee & Eva Kühn, May 2004

RDF-triples are almost identical to the associative array, or key:value pair-based structure we're used to; triples are just a slightly more atomic way of describing the information. A statement of <subject, predicate, object> can be thought of as saying the subject contains the predicate:object association. See also the Notation3 (N3) format for triples.

Hydranode

Hydranode is more complete than the nodal reduction algorithm and already supports multiplexed and load-balanced communications over a diverse range of protocols, even though it may no longer be under development. In fact, any content distribution system that is protocol-independent can easily be turned into a work reduction system similar to the nodal model's approach, because any processeses that can be broken up into arbitrarily small work units are completed in the same way as sending or receiving any packet.

Tripoli

Tripoli is a GPL project written in Python that implements a TripleSpace over the Twisted infrastructure, which is an event-driven network programming framework under the MIT License.

Perl Object Environment

POE was originally developed as the core of a persistent object server and runtime environment. It has evolved into a general purpose multitasking and networking framework, encompassing and providing a consistent interface to other event loops. POE is a Perl equivalent to Tripoli.