# OPC Classic

<dl class="api-definition">
<dt>Concept</dt>
<dd><a href="/docs/development/opcua/client/opc-classic">OPC Classic</a></dd>
</dl>

| Type | Description |
|---|---|
| [OpcAcknowledgeableCondition](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcacknowledgeablecondition/) | Represents a snapshot of a 'Opc.UaFx.OpcAcknowledgeableConditionNode'. |
| [OpcAggregateType](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcaggregatetype/) | Specifies an aggregate function of the OPC UA namespace, whose identifier [GetTypeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcaggregate/members#gettypeid) provides. |
| [OpcClassicAuthenticationLevel](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicauthenticationlevel/) | Defines the supported authentication level to control how much security a client or server wants from its SSP. |
| [OpcClassicDataAccessOptions](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicdataaccessoptions/) | Provides a set of options which apply to the communication with the data access layer of OPC Classic. |
| [OpcClassicDiscoveryClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.classic.opcclassicdiscoveryclient/) | Represents a client which discovers the OPC Classic servers registered on a host. |
| [OpcClassicEndpointDescription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicendpointdescription/) | Represents an endpoint of an OPC Classic server: the server and the interface specifications to use to communicate with it. |
| [OpcClassicIdentity](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicidentity/) | Represents the identity of a user used to authenticate at the host of an OPC Classic server using DCOM. |
| [OpcClassicImpersonationLevel](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicimpersonationlevel/) | Defines the degree of authority the application grants other applications to use its identity when it calls them. |
| [OpcClassicInterface](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicinterface/) | Represents an interface specification of OPC Classic (e.g. OPC Data Access 2.0) which an OPC Classic server implements (see [OpcClassicInterfaces](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicinterfaces/)). |
| [OpcClassicInterfaceCollection](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicinterfacecollection/) | Represents a collection of [OpcClassicInterface](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicinterface/) instances keyed by their [Identifier](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicinterface/members#identifier). |
| [OpcClassicOrganization](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.classic.opcclassicorganization/) | Defines the type of namespace organization to use while browsing the address space. |
| [OpcClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/) | Provides session based methods to access OPC UA server services. |
| [OpcClientIdentity](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclientidentity/) | Represents a user identity which is defined by a user name and a password. |
| [OpcClientInterfaces](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclientinterfaces/) | Defines additional options to be used for the different interfaces consumed by the [OpcClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/). |
| [OpcClientSecurity](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclientsecurity/) | Defines the different security configurations supported by the [OpcClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/). |
| [OpcClientStateChangedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclientstatechangedeventargs/) | Provides the event data for the [StateChanged](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/statechanged) event. |
| [OpcEventReceivedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventargs/) | Provides the event data for the [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/eventreceived), [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#eventreceived) and [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#eventreceived) events. |
| [OpcHistoryValue](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opchistoryvalue/) | Represents a value of the history of a node. |
| [OpcNamespace](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnamespace/) | Represents a nominal space used to categorize information like nodes, types, identifiers, etc. under a logical topic. |
| [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | Defines an identifier for a node in the address space of an OPC UA Server. |
| [OpcNodeInfo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnodeinfo/) | Provides properties and methods for the examination of the attributes and references of a node. |
| [OpcStatus](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatus/) | Provides information about the outcome of an operation. |
| [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) | Provides mechanisms to monitor a set of attributes (= node data) and (node-related) events using notifications being reported from the server to the client. |
| [OpcValue](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcvalue/) | Stores a value optionally associated with status and timestamp information. |