An activity is a piece of content (e.g., text, image, video) that a user shares through a consumable stream of activities. This stream may consist of the activities of a single user or an amalgamation of many people, sorted by criteria such as friendships or location (for example, a user’s Facebook news feed contains a series of activities from her friends).

AJAX is an acronym for Asynchronous JavaScript and XML, although many implementations favor JSON over XML. It defines a series of interrelated web development technologies that allow developers to construct dynamic web applications.

More information: http://en.wikipedia.org/wiki/Ajax_(programming).

In terms of a social profile, a connection is a reciprocated relationship between two individuals. Both parties have to accept this “friendship” link to build a connection. Being part of a connection usually gives both individuals additional privileges to view and consume more information about each other from their respective profiles.

Container is the term used to describe a social networking site that allows developers to build applications on top of it. Well-known social networking containers are Facebook, YAP, iGoogle, and Orkut.

Distributed web frameworks, as used in this text, refer to a series of open protocols and specifications that promote the syndication of content and entity cross-communication on the Web.

In the context of OpenSocial, all applications that follow the gadget XML specification are considered gadgets.

Headless requests are processes that run without requiring user interaction. In the case of services such as OAuth, the term headless refers to a process in which a user authorizes the application once and then the service, in subsequent requests, makes changes to or performs some action on the user’s data without him being involved. The service does this by storing his access token and using it to make additional requests for the duration of time that the token is valid.

An Internationalized Resource Identifier is a generalization of a URI. Instead of being limited to the use of the ASCII character set, an IRI may contain characters from the universal character set (Unicode/ISO 10646).

More information: http://en.wikipedia.org/wiki/Internationalized_Resource_Identifier.

Link-based Resource Descriptor Discovery is an open protocol that defines methods for obtaining information about a resource through the use of a URI, much like how WebFinger is used to obtain information about a person through the use of her email address. The latest specification documentation for LRDD is available at http://tools.ietf.org/html/draft-hammer-discovery-06.

In the context of a social networking application, such as an OpenSocial gadget, the owner is the individual or company who created the application being used by a viewer.

Partuza is an example social networking site that is built off OpenSocial and Apache Shindig. The project home for Partuza is http://code.google.com/p/partuza/.

Representational State Transfer is a specification that defines an HTTP communication architecture to which web-based services should conform. When a service implements the REST architecture, it is said to be RESTful.

More information: http://en.wikipedia.org/wiki/Representational_State_Transfer.

A remote procedural call is a type of protocol that allows one computer to execute some program or script on another computer, even outside its own address space. This allows the client machine to leverage the existing programs on the server computer. The server will execute the requested script and return back the result of the execution to the client machine.

More information: http://en.wikipedia.org/wiki/Remote_procedure_call.

Those working with client-side languages such as JavaScript should have an intimate understanding of the same-origin policy. At a basic level, this policy states that scripts can access the methods and properties on their own domain but are restricted from accessing those methods and properties on other domains.

More information: http://en.wikipedia.org/wiki/Same_origin_policy.

The semantic web is essentially the utilization of specified metadata on a web page to allow machines to more effectively parse its content. Semantic markup allows for a much richer understanding of the page’s content (i.e., what it is attempting to serve up to users) and helps construct a deep “web of data.”

More information: http://en.wikipedia.org/wiki/Semantic_web.

Shindig is an OpenSocial container that allows a developer or site owner to quickly begin hosting OpenSocial gadgets on his site. This is the de facto method for integrating OpenSocial gadgets in a service. Shindig is an Apache project whose home is located at http://shindig.apache.org/.

A social network is a site that allows users to engage with one another online and uses an extensive profile system to identify users within the system. One popular example is Facebook.

Social graph is the term generally used to denote the links between two or more individuals within a social network. A user may have numerous interconnected social graphs that span many different social networks.

More information: http://en.wikipedia.org/wiki/Social_graph.

A social entity is a construct that resides within a user’s social graph. Unlike the “person” links that are traditionally associated with a social graph, an entity is a website, team, cause, or any number of other “things” that a user has indicated that she is a fan of or involved in. It is a generic container to denote additional information about a user other than friendship links.

In the context of a social networking application, such as an OpenSocial gadget, the viewer is the individual who is currently using the application constructed by the application owner.

eXtensible Resource Descriptor Sequence is an XML format whose purpose is to provide metadata about some resource. The main use of this type of discovery, besides providing data about the resource, is to deliver services that are associated with the resource.

More information: http://en.wikipedia.org/wiki/XRDS.

eXtensible Resource Identifier is a scheme that defines a method for creating structured, self-describing identifiers that may be extended to many uses by including direct metadata about an object. The standard syntax and discovery format is domain-, location-, application-, and transport-independent, meaning that it can be shared among different domains, directories, and protocols.

More information: http://en.wikipedia.org/wiki/XRI.

The term viral stems from application development, and generally means an application that maintains greater than a 1:1 growth. If each user of an application invites two people, then it will experience a viral growth trend, or in more popular parlance, “go viral.”

More information: http://en.wikipedia.org/wiki/Viral_phenomenon.

YAML is an acronym for Yet Another Markup Language. Within the confines of Google App Engine, where YAML is referenced, it is used as an application configuration and control file.

More information: http://en.wikipedia.org/wiki/YAML.

YAP is an acronym for Yahoo! Application Platform. It is an OpenSocial 0.9–compliant container that showcases user-built applications across many of the Yahoo! sites and services.

More information: http://developer.yahoo.com/yap.