OPC UA Application URI Derivation

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Every OPC UA application (client or server) needs an application URI, which uniquely identifies the application instance in the system.

Applications based on QuickOPC determine their application URI in the following way:

  1. If the application manifest contains a non-empty ApplicationUriString property, it will be used as the application URI.
  2. Otherwise, the application URI is automatically generated, using a template string from the ApplicationUriTemplateString property in the application parameters.

The application URI template string consists of characters that are copied literally to the output string, and macros, which are replaced by values provided by QuickOPC. When the macro is expanded, it is URL-escaped before it is inserted into the output string, so that a correct URI can be formed. Macro replacements have the syntax $(name), where name is one of the names defined in the following table.

Category Name Description
Common HostName Host name of the local computer.
ModuleName Name of the main module for the current process.
ProcessId Numeric Id of the current process.[1]
ProcessName The name of the current process.
Application Assembly SimpleName Simple name of the application assembly.
Version Version number of the application assembly.
Culture Supported culture of the application assembly.
PublicKeyToken Public key token of the application assembly.
AssemblyName Display name of the application assembly (such as "ExampleAssembly, Version=, Culture=neutral, PublicKeyToken=null").
AssemblyTokens A combination of SimpleName, Version, and Culture, separated by colons. The trailing tokens are left out together with the colons that precede them, if they are at default values ("" for the Version, and "neutral" for the Culture).
Application Version Info CompanyName Name of the company from the application version info.
FileVersion File version number from the application version info.
Language Default language string from the application version info.
NameToken Internal name from the application version info, without the ".exe" extension if present.
ProductVersion Product version number from the application version info.
ShortFileVersion The part of FileVersion before the first space character (' ').
VersionInfoTokens A combination of NameToken, ShortFileVersion and Language, separated by colons. The trailing tokens are left out together with the colons that precede them, if they are at default values ("" for the ShortFileVersion, and "Language Neutral" for the Language).

The information in the "Application Assembly" and "Application Version Info" categories may not always be available - it depends on factors such as the type of application and the hosting process. For this reason, the template string can have one or more sections, separated by a semicolon (';'). If three or more sections are present, they are interpreted like this:

  • If the application version info is available, the last section from the end is used.
  • Otherwise, if the application assembly information is available, the second section from the end is used.
  • Otherwise, the third section from the end is used.

If there are fewer sections, the first section that would be to the right of the position indicated by the above rules is used. This algorithm also means that you can use just one section, and this section will then always be used.

The default application URI template string (in QuickOPC 2023.1) is as follows:

  1. Normally not used, as it is not stable enough for the most purposes. Intended for "transient" OPC UA applications.