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Unified Communications Client API Terminology

This article defines some terminology commonly used with Microsoft’s Unified Communications solution, Office Communication Server 2007.

Access Control EntryAn individual member of an Access Control List. The scope of the Access Control Entry (ACE) can be as granular as an individual subscribing user or as complete as the scope of all possible users.

Access Control ListA list of URI, domain, company, federation, or public scope container members. The Access Control List (ACL) defines the rules for access to a local user’s published presence information.

alertOne-way messaging, without SIP dialog.

call controlOperations such as transferring a (computer-to-computer, computer-to-phone, or phone-to-phone) media session call to another party, placing a call on hold, or cancelling the hold in such a session. It is also known as session call control. Call control is represented by the IUccSessionCallControl interface.

categoryExtensible abstract data types for publication and subscription of data used in real-time communications and collaborations.

category instanceAn instance of a category holding a piece of data used in real-time communications and collaborations. Category instance is represented by the IUccCategoryInstance interface.

category contextA collection of instances of a given category name belonging to a particular publisher known as the presentity of the category instances. Category context is represented by the IUccCategoryContext interface.

conference sessionAn association of a group of users engaged in a conference call. Conference session is a transmission-free session. Conference participants interact with each other by establishing transmission-based communication sessions (such as instant messaging, audio/video, or application sessions) with one or more multipoint control units (MCU) provided by the conference. All participants communicate with each other through the conference MCU. The network formed by participant endpoints has a star topology with an MCU situated at the center. The conference session encapsulates the operations for managing a conference and maintaining its roster.

containerA strongly typed category instance that provides an Access Control List (ACL) that defines access to a user’s published presence information. A container is represented by the IUccContainer interface.

CSTAComputer Supported Telecommunications Applications. An international standard established by the European Computer Manufacturers Association (ECMA) that specifies an application’s interface and protocols for telephony integration in a communications network.

device managementInspection and enumeration of locally supported devices for capturing and rendering media.

distribution groupDistribution groups are used with e-mail applications to send e-mail messages to the members of the group. Distribution groups play no role in security (you do not assign permissions to distribution groups), and you cannot use them to filter group policy settings. Distribution groups can be subscribed to and published in a custom Unified Communications Client API application.

endpointRepresents a user in a particular communication mode or network location. The user is identified by a SIP URI, such as “”. An endpoint of that user can be identified by the user’s SIP URI plus an endpoint ID or a Globally Routable User-Agent URI (GRUU). Endpoint IDs for a given SIP URI are unique. The endpoint is represented by the IUccEndpoint interface.

focusA logical component of Office Communications Server responsible for managing a single active conference. The server implements a star-shaped topology to manage a conference with the focus as the center. Each participant is represented by an endpoint connected through session channel to the central focus. Audio, video, and text streams are directed from the endpoints to the focus. The focus broadcasts the incoming media streams to all the participant endpoints. Endpoints do not create channels directly to other endpoints.

focus factoryA logical component of Office Communications Server responsible for scheduling, activating, deactivating, and deleting conferences.

in-band provisioningThe process of provisioning a client with all subscribed well-known and custom categories from Office Communications Server using an established SIP communications channel. The process starts when a client registers with Office Communications Server. All subscribe categories are provisioned initially. As category data changes, the client is updated using this process. In-band provisioning makes it possible for a client to entirely avoid the need to persist application data at the local computer level.

media channelA connection through which media (voice, video, or application-defined data) are transmitted between a pair of endpoints. Media channel is represented by the IUccMediaChannel interface.

media connectivityA media connection between endpoints across firewalls. A Unified Communications Client API client enables the media connectivity by selecting a supported media connectivity server, also known as Media Relay.

media negotiationExchange media description. Accepts, reconciles, or rejects any discrepancies between a pair of endpoints.

multipoint control unitsA property of a conference, also known as MCU. Conference participants communicate with each other by establishing media sessions with mode-specific MCUs.

Office Communications ServerMicrosoft Office Communications Server 2007 provides SIP-based services for unified real-time communications. Unified Communications Client API serves as the client platform for building and deploying real-time communications client applications to work with this server.

Office CommunicatorMicrosoft Office Communicator 2007 is a real-time communications client. It supports contact management and presence monitoring, instant messaging, voice calling, video chatting, conferencing, and telephony integration. This client application is built on the Unified Communications Client API framework.

participantA user or communication entity in a media or transmission-based (instant messaging, audio/video, telephony, or application) session or a transmission-free (conference) session. It is also referred to as session participant. A participant is identified by a SIP URI; for example, “”. Participant is represented by the IUccSessionParticipant interface.

participant endpointThe endpoint by which a session participant interacts with other participants. In a conference session, a participant can have different participant endpoints to support instant messaging, audio/video, application-sharing, and telephony integration. An application can also choose participant endpoints to control how a media or transmission-based session is established. For example, two users are in an IM session using their laptop computers, while they are also logged on from their desktop computers. When one party adds audio to their communications, the application might want to choose the remote participant’s endpoint originating from the remote laptop computer. Otherwise, the remote participant receives the notification of the incoming audio invitation on both the desktop and laptop computers.

media sessionAlso known as transmission-based session. It refers to an association of two or more users engaged in such activities as instant messaging (IM), voice calling, video chatting, and application-sharing. Unlike a conference (which is transmission-free) session, data is exchanged between a pair of participants in a media session either through explicitly established media channels between the two endpoints of the participants or as the body of a SIP message.

presencePresence is a service that can support the following functions:- Publish presence information.- Query the presence of a specified user. This corresponds to a one-time retrieval of the publisher’s current presence information.- Subscribe to the presence of a user. This involves receiving the specified presence information and the ensuing updates of the presence information.

In Unified Communications Client API, presence is supported by a general-purpose framework for publication, subscription, and query of category instances.

presence informationIndicates the availability of a user for real-time communication activities. It also indicates the level of the user’s activity for the device publishing the presence information. The presence information can be as simple as whether the user is online or offline or as complex as a user’s meeting schedule.

The user’s presence information is an aggregate published by all the communication devices that he or she is using.

presentityThe entity (a user, application, or service) who publishes the presence information to allow subscribers to receive its presence information. A presentity is identified by a SIP URI (“”). Presentity is represented by the IUccPresentity interface.

publicationMaking information or data available for other users. The information or data can be presence information, contact information, and any application-specific custom data. In Unified Communications Client API, publishable information or data is represented by category instances.

queryOne-time receipts of published information or data. Query takes place in a polling subscription.

remote call controlA feature of telephony integration. A Unified Communications Client API application can manage and control telephone calls, including making outbound telephone call, accepting, forwarding, or rejecting (if supported by the local PBX) inbound telephone calls, and transferring an ongoing telephone call to another party. Remote call control represents an audio session using telephone sets. The telephone set is represented by a proxy endpoint and the assigned owner of the telephone is the controlling SIP endpoint.

sessionA session implies an association of two or more participants. In Unified Communications Client API, it is a SIP protocol based communication session involving two or more endpoints. A session supporting instant messaging is of the instant messaging session type. A session supporting audio/video media is of the audio/video session type. A session supporting custom data exchange or application-sharing is known as the application session. A session involving multiple participants and a conference focus is the conference session. In a conference session, participants communicate with each other through a media-specific multipoint control unit (MCU) of the conference. A non-conference session is also referred to as a media session. Session is represented by the IUccSession interface.

session call controlSee Call control

SIP proxySee SIP server

SIP registrarSee SIP server

SIP serverCoordinates with Unified Communications Client API clients so that one client can discover another client and establish media sessions or conference sessions. Through registration, the SIP server also helps clients maintain communications security, manage presence information, and persist users’ contact lists.

A SIP server can also act as a SIP proxy that routes or redirects SIP messages across SIP clients. It can also maintain a database of network locations of SIP clients and ensure that all SIP clients update their location information.

A SIP server handling user registration is also known as SIP registrar. Microsoft Office Communications Server serves both as a SIP registrar and a SIP proxy.

subscriptionReceiving information or data and their updates published by other users or self. Subscribers and publishers must agree with each other on what information or data and the ensuing update that a subscriber can receive. Subscription takes place in a roaming subscription session. A subscriber does not receive data or updates when the subscription session ceases to exist.

subscriberA user who has subscribed to the presence of a registered user.

Unified Communications (UC)A Microsoft real-time SIP-based communications technology based on Office Communications Server to enable real-time communications using:

– Office Communicator 2007- Office Communicator Web Access- Office Live Meeting 2007- Office Communicator Automation API- Unified Communications AJAX API- Unified Communications JavaScript Libraries- Unified Communications Client API- Unified Communications Managed API

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