OPC（用于过程控制的 OLE）中接口 IOPCServer、IOPCDataItem、IOPCGroup 的作用是什么
我目前是 OPC（用于过程控制的 OLE）的新手。我想了解OPC中的IOPCServer、IOPCDataItem、IOPCGroup接口。它们的用途是什么？他们在 OPC 客户端和 OPC 方面的作用是什么？ OPC服务器和什么方法&这些接口包含哪些属性？您能否为我提供上述问题的答案，或者您能否为我提供获取上述主题知识的链接？
I am currently new in OPC ( OLE for process control). I want to know about the interfaces IOPCServer, IOPCDataItem, IOPCGroup interfaces in the OPC. What are they used for & what is their role in terms of OPC Client & OPC Server & what methods & properties these interfaces conatins ? Can you provide me the answer for the above questions or can you provide me the link through which I can get the knowledge of the above topics ?
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您可能正在谈论 OPC DA（数据访问）接口。您必须知道您的目标是哪个版本的 OPC DA（最有可能的版本是 2.05a 和 3.0）。
接口规范由 OPC 基金会提供，需要付费会员才能下载规范。请参阅：http://www.opcfoundation.org/ Downloads.aspx?CM=1&CN=KEY&CI=274 ;或者您可以免费在线浏览规格，四处搜索，例如：http://www.doc88.com/p-67617868554.html
从 OPC 基金会下载 OPC DA 可再发行包（即使对非会员也是免费的）。然后您可以在包含的 IDL 文件中看到完整的 API 定义。
无论如何，IOPCServer 是“根”接口，客户端通过它进行连接并获取对所有其他对象的引用。实际上它具有连接类型对象的语义。它的方法提供一些基本服务（例如服务器状态管理），以及浏览所有服务项目及其属性。
IOPCGroup 提供了一种对数据项进行分组以进行集体读写的方法。如果以相同周期读取并且具有相同死区的项目，则组是一个集合。它包含用于添加/删除项目以及同步或异步读取它们的方法。
IOPCDataItem 我从未见过（在 DA 2.05 或 DA 3.0 中）。您是否可以参考IOPCItemIO，这是直接读取/写入项目而无需创建组的方式（仅在3.0中）？
You're probably talking about the OPC DA (Data Access) interfaces. You would have to know which version of OPC DA you're targeting (most likely versions are 2.05a and 3.0).
The interface specifications are served by OPC Foundation, and they require a paid membership to download the specifications. See: http://www.opcfoundation.org/Downloads.aspx?CM=1&CN=KEY&CI=274 ; or you might be able to catch a glimpse of the specs for free online, search around, for example see: http://www.doc88.com/p-67617868554.html
Download the OPC DA redistributable package from OPC Foundation (this is free even for non-members). Then you can see the full API definitions in the included IDL files.
Anyway, IOPCServer is the "root" interface through which the client connects and gets the references to all the other objects. Practically it has the semantics of a connection-type object. Its methods provide some basic services (e.g. server state management), as well browsing all the served items and their properties.
IOPCGroup provides a way of grouping data items for collective reads and writes. A group is a collection if items which are read with the same cycle, and have the same deadbands. It contains methods for adding/removing items and reading them synchronously or asynchronously.
IOPCDataItem I have never seen (in DA 2.05 or DA 3.0). Could you be referring to IOPCItemIO, which is the way to read/write items directly without creating groups (in 3.0 only)?