This document describes Session Initiation Protocol (SIP), an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants. These sessions include Internet telephone calls, multimedia distribution, and multimedia conferences.

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SIP: Session Initiation Protocol

The term “Linked Data” refers to a set of best practices for publishing and connecting structured data on the Web. These best practices have been adopted by an increasing number of data providers over the last three years, leading to the creation of a global data space containing billions of assertions— the Web of Data. In this article, the authors present the concept and technical principles of Linked Data, and situate these within the broader context of related technological developments. They describe progress to date in publishing Linked Data on the Web, review applications that have been developed to exploit the Web of Data, and map out a research agenda for the Linked Data community as it moves forward.

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Linked Data - the story so far

The World Wide Web has enabled the creation of a global information space comprising linked documents. As the Web becomes ever more enmeshed with our daily lives, there is a growing desire for direct access to raw data not currently available on the Web or bound up in hypertext documents. Linked Data provides a publishing paradigm in which not only documents, but also data, can be a first class citizen of the Web, thereby enabling the extension of the Web with a global data space based on open standards - the Web of Data. In this Synthesis lecture we provide readers with a detailed technical introduction to Linked Data. We begin by outlining the basic principles of Linked Data, including coverage of relevant aspects of Web architecture. The remainder of the text is based around two main themes - the publication and consumption of Linked Data. Drawing on a practical Linked Data scenario, we provide guidance and best practices on: architectural approaches to publishing Linked Data; choosing URIs and vocabularies to identify and describe resources; deciding what data to return in a description of a resource on the Web; methods and frameworks for automated linking of data sets; and testing and debugging approaches for Linked Data deployments. We give an overview of existing Linked Data applications and then examine the architectures that are used to consume Linked Data from the Web, alongside existing tools and frameworks that enable these. Readers can expect to gain a rich technical understanding of Linked Data fundamentals, as the basis for application development, research or further study.

Linked Data: Evolving the Web into a Global Data Space

The present invention is directed to an integrated implementation framework and resulting medium for knowledge retrieval, management, delivery and presentation. The system includes a first server component that is responsible for adding and maintaining domain-specific semantic information and a second server component that hosts semantic and other knowledge for use by the first server component that work together to provide context and time-sensitive semantic information retrieval services to clients operating a presentation platform via a communication medium. Within the system, all objects or events in a given hierarchy are active Agents semantically related to each other and representing queries (comprised of underlying action code) that return data objects for presentation to the client according to a predetermined and customizable theme. This system provides various means for the client to customize and “blend” Agents and the underlying related queries to optimize the presentation of the resulting information.

System and method for knowledge retrieval, management, delivery and presentation

The Internet has evolved greatly from its original incarnation. For instance, the vast majority of current Internet usage is data retrieval and service access, whereas the architecture was designed around host-to-host applications such as telnet and ftp. Moreover, the original Internet was a purely transparent carrier of packets, but now the various network stakeholders use middleboxes to improve security and accelerate applications. To adapt to these changes, we propose the Data-Oriented Network Architecture (DONA), which involves a clean-slate redesign of Internet naming and name resolution.

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A data-oriented (and beyond) network architecture

The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. It is a generic, stateless, protocol which can be used for many tasks beyond its use for hypertext, such as name servers and distributed object management systems, through extension of its request methods, error codes and headers [47]. A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred.

Hypertext Transfer Protocol -- HTTP/1.1

A universal plug and play (UPnP) device makes itself known through a set of processes—discovery, description, control, eventing, and presentation. Following discovery of a UPnP device, an entity can learn more about the device and its capabilities by retrieving the device's description. The description includes vendor-specific manufacturer information like the model name and number, serial number, manufacturer name, URLs to vendor-specific Web sites, etc. The description also includes a list of any embedded devices or services, as well as URLs for control, eventing, and presentation. The description is written by a vendor, and is usually based on a device template produced by a UPnP forum working committee. The template is derived from a template language that is used to define elements to describe the device and any services supported by the device. The template language is written using an XML-based syntax that organizes and structures the elements.

XML-based template language for devices and services

A schema-based service for Internet access to per-user services data, wherein access to data is based on each user's identity. The service includes a schema that defines rules and a structure for each user's data, and also includes methods that provide access to the data in a defined way. The services schema thus corresponds to a logical document containing the data for each user. The user manipulates (e.g., reads or writes) data in the logical document by data access requests through defined methods. In one implementation, the services schemas are arranged as XML documents, and the services provide methods that control access to the data based on the requesting user's identification, defined role and scope for that role. In this way, data can be accessed by its owner, and shared to an extent determined by the owner.

Schema-based services for identity-based data access

A network system includes a content provider connected to local service providers via an interactive distribution network, such as the Internet. The local service providers facilitate delivery of the content from the content provider to multiple subscribers. The local service providers schedule delivery of frequently requested content from the content provider prior to a peak time when the subscribers are likely to request the content. The content is downloaded from the content provider during the off-peak hours and cached at the local service providers for serving to the subscribers during the ensuing peak time. In this manner, the frequently requested content is already present at the local service providers and ready to be served to the subscribers before they actually request it. When the content is finally requested, the data is streamed continuously in real-time for just-in-time rendering at the subscriber computer. Another aspect of is invention involves supplementing content delivery over the Internet with delivery of content over a secondary network, such as a broadcast satellite network. The supplemental broadcast link offers additional bandwidth at a fraction of the cost that would be incurred if the local service provider installed additional Internet connections, such as T1 or T3 connections.

Pull based, intelligent caching system and method for delivering data over a network

A computer method and system for passing a pointer to an interface from a server process to a client process. In a preferred embodiment, the server process instantiates an object that has multiple interfaces. The server process identifies an interface to pass to the client process and creates a stub object for receiving a request to invoke a function member of the interface and for invoking the requested function member upon receiving the request. The server process then sends an identifier of the stub to the client process. When the client process receives the identifier of the stub, it instantiates a proxy object for receiving requests to invoke a function member of the interface and for sending the request to the identified stub. The client process can then invoke the function members of the interface by invoking function members of the proxy object. The proxy object sends a request to the identified stub. The identified stub then invokes the corresponding function member of the interface.

Paul J. Leach

Papers

Hypertext Transfer Protocol -- HTTP/1.1

XML-based template language for devices and services

Schema-based services for identity-based data access

Pull based, intelligent caching system and method for delivering data over a network

Method and system for network marshalling of interface pointers for remote procedure calls