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.
XFM linkages are the first version associated with Bentley Map Select Series 1. These linkages exist on elements, and on potential non-geometric reference elements of type igds_xfmstore.
The primary form of XFM linkages contains Universally Unique Identifier (UUID) values which are used to associate non-graphical XFM feature store elements with other graphical elements, and with each other in a one-to-one relationship.
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.
A secondary form of XFM linkage simply stores XFM XML information on an element. Both the primary and secondary normalized forms of XFM data can be read and written with the DGNV8 format.
If the linkage is one of these types, then these attribute list item names are used to specify the values for the linkage:
|
Linkage Parameter |
Contents |
|---|---|
| xfm_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 and may be used to construct XFM data for an element when writing. (However, it may be calculated when writing if not supplied.) This attribute has an alias as igds_xfm_data_prefix. Range: Valid 4-byte binary encoded string Default: No default |
| xfm_parent_uuid |
A UUID for the parent XFM feature for this element in a potential XFM feature hierarchy. If this element is the root XFM feature, then this linkage attribute will be a UUID of all zeros. This attribute has an alias as igds_xfm_parent_uuid. Range: Any UUID value in string format Default: UUID of all zeros |
| xfm_root_uuid |
A UUID for the root XFM feature for this element in a potential XFM feature hierarchy. If this element is the root XFM feature, then this linkage attribute will be the same as the xfm_uuid linkage attribute. This attribute has an alias as igds_xfm_root_uuid. Range: Any UUID value in string format Default: The same value as the xfm_uuid attribute |
| xfm_uuid |
A UUID for this XFM feature element, acting as an identifier for referencing XFM data. When writing, this linkage attribute is required to create an XFM UUID linkage. This attribute has an alias as igds_xfm_uuid. Range: Any UUID value in string format Default: No default |
| xml_data_prefix |
A binary encoded string value for the bytes prefixing XML data in a secondary form XFM XML linkage. This is used by the Writer to recreate the same XFM XML linkage read by the Reader, however, this data may be calculated by the writer if not supplied. Range: Valid 32-byte binary encoded string Default: No default |
| xml_data |
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 |