Choose Elements

Each element type in the attribute file can be reported on but a block of commands must be included in the configuration file. The block starts with the type of the element, and ends with the corresponding END_ command. Between these two, include the attributes that they require.

For example:

BRANCH

    ALL_ATTRIBUTES

    ALL_UDAS

END_BRANCH

VALVE

    NAME

    SPREF

    :MANUFACTURER

END_VALVE

Each element found when Export-DGN is scanning the Design database according to the export commands is checked so see if it is one of those listed in the configuration file. If it matches, a MicroStation Cell is added to the dgn file. Since the MODEL is hierarchical, with, for example ZONEs containing PIPEs containing BRANCHes containing VALVEs, this, by default, creates Cells within Cells in the dgn file, this can lead to two problems:

• There is a limit on the amount of data that can be put in a MicroStation Cell. A ZONE almost certainly exceeds this limit

• Some applications that read dgn files may not interpret nested cells correctly.

To deal with these situations it is possible to tell Export-DGN to handle some elements differently, and either to use an empty cell, or a cell containing geometry, but not nested cells. If the user uses the EMPTY qualifier on an element line, for example

ZONE EMPTY

NAME

END_ZONE

Export-DGN creates an almost empty cell in the dgn file, and link the attributes to that. As the cell is almost empty it does not exceed the size limit. The cell does not completely empty as many dgn file readers reject completely empty cells. (If necessary, a line of zero length is put in the cell). It is often better to use the facilities to report on the attributes of another element (described in Attributes of Other Elements) to report attributes of these very high-level attributes.

If the NONEST qualifier on an element line is used then Export-DGN writes a cell to the dgn file which may contain geometry, but does not contain the cells of other elements from the configuration file (it may contain cells produced for geometry defined in AVEVA E3D Design as facets). It is recommend that the user only uses this option if the system reading the dgn file cannot cope with the default NEST option.

An example of a possible use of NONEST is when the user wants to have cells for valves, but to gather all the geometry within a branch except for the valves into a branch-cell. The user can express this as:

BRANCH NONEST

    ALL_ATTRIBUTES

END_BRANCH

VALVE

    ALL_ATTRIBUTES

    NAME OF BRANCH

END_VALVE

If a particular cell would exceed the maximum possible size, Export-DGN excludes some of its contents from the cell. All the geometry is included in the file, but it is not included in the cell structure. If this happens, a warning message is output to the log-file.