How the XML is Validated

Validation at Run-Time

Connext DDS validates the input XML files using a builtin Document Type Definition (DTD).

You can find a copy of the builtin DTD in <NDDSHOME>/resource/schema/rti_dds_qos_profiles.dtd. (This is only a copy of what the Connext DDS core uses. Changing this file has no effect unless you specify its path with the <!DOCTYPE> tag, described below.)

You can overwrite the builtin DTD by using the XML tag, <!DOCTYPE>. For example, the following indicates that Connext DDS must use a DTD file from a user’s directory to perform validation:

<!DOCTYPE dds SYSTEM "/local/joe/rti/dds/mydds.dtd">

The DTD path can be absolute, or relative to the application's current working directory.

If the specified file does not exist, you will see the following error:

RTIXMLDtdParser_parse:!open DTD file

If you do not specify the DOCTYPE tag in the XML file, the builtin DTD is used.

The XML files used by Connext DDS can be versioned using the attribute version in the <dds> tag. For example:

<dds version="5.x.y">
   ...
</dds>

Although the attribute version is not required during the validation process, it helps to detect DTD incompatibility scenarios by providing better error messages.

For example, if an application using Connext DDS 5.x.y tries to load an XML file from Connext DDS 4.5z and there is some incompatibility in the XML content, the following parsing error will be printed:

ATTENTION: The version declared in this file (4.5z) is different from the version of Connext DDS (5.x.y). If these versions are not compatible, that incompatibility could be the cause of this error.