XML-based Feature Modelling (XFM) data exists in two known versions in version 8 Design files. Both forms consist of element attributes and potential additional elements which may be referenced to provide additional XFM information or details. Both versions are read with the DGNV8 Reader as attributes on elements and reference elements, which provides a normalized form of XFM features.
Note: For a more XFM-oriented representation of the XFM data, the Bentley Map XFM Design format may be preferable. The Bentley Map XFM Design format reader treats the XFM feature names as the feature types for elements with XFM data. It also merges XFM data from reference elements and flattens any XML fragments into user attributes on the features created by the reader.
XFM XAttributes are the second version associated with Bentley Map Select Series 3 and newer. These XAttributes exist on elements, and on potential reference elements of type igds_polygon_collection and igds_nongeom_collection. The primary form of XFM XAttributes contains either Universally Unique Identifier (UUID) values or element identifiers which are used to associate non-graphical XFM feature store elements with other graphical elements.
XFM features may actually be represented by a hierarchy of elements related by XFM XAttributes, and it is the relationship of an element with XFM properties and an associated element that may be a part of this combination of graphics and properties. The focus of the DGNV8 Reader is to read XFM feature stores for the purpose of providing XFM properties with a specific graphical element in an XFM feature hierarchy.
Note: Select Series 3 related XFM XAttributes are currently not supported for writing.
If XFM XAttributes exist, then these attribute list item names are used to specify the values for them:
| Linkage Parameter | Contents |
|---|---|
| attr_id | An identifier for the Xattribute. |
| data |
A binary encoded string value for the unknown data associated with uninterpreted Xattribute types. Range: A valid context-specific variable length binary encoded string Default: No default |
| data_prefix |
A binary encoded string value for the bytes prefixing the core data of an XFM item for an element. This is application-specific. This attribute has an alias as igds_xfm_data_prefix. Range: A valid context-specific variable length binary encoded string Default: No default |
| feature |
This attribute is used when reading an XFM feature element or XFM reference element. It indicates the name of the XFM feature. This attribute has an alias as igds_xfm_name. Range: A UNICODE (UTF-16) encoded string Default: No default |
| handler_id |
This is a number representing a sub-type of an XAttribute handler. For each handler_type these are context-specific values further specify what is stored. Range: Any positive integer Default: No default |
| handler_type |
This is a number representing a type of an XAttribute handler. This value is similar to the userId property of User Linkages. Range: Any positive integer Default: No default |
| ref_elem_id |
The identifier of an element for referencing XFM data. Range: Any positive integer Default: No default |
| type |
This is a string representing the general type of an XAttribute. Range: xattr_binary_xml | xattr_proxy | xattr_unknown | xattr_xml etc. Default: xattr_unknown |
| url |
The UNICODE (UTF-16) encoded string for an XFM feature URL fragment. This is typically found on an XFM reference feature. However, it may appear on other features that contain XFM data. Range: Any valid URL String. Default: No default |
| xfm_uuid |
A UUID for this XFM feature element, acting as an identifier for referencing XFM data. This attribute has an alias as igds_xfm_uuid. Range: Any UUID value in string format Default: No default |
| xml |
A UNICODE (UTF-16) encoded string containing the XML data in a secondary form XFM XML linkage. Range: Any valid XML string Default: No default |