This article provides a brief overview of Item Types technology in MicroStation CONNECT
The information presented here is an informal guide to Item Types. Its intended audience includes MicroStation administrators and MicroStation developers.
There's a useful table in MicroStation CONNECT help that compares various annotation technologies, including Item Types and Text Fields. To find this table in MicroStation help, search for Comparing Text Field, Label, Note, Table, Report, Item, Item Type, and Item Sets.
MicroStation CONNECT help is available on line. Here's that comparison table in MicroStation Help.
To dispel confusion, Item Sets are an earlier and different technology. They are unrelated to Item Types other than having a similar name.
Item Types, introduced with MicroStation CONNECT, are meta data that define data types. In other words, a schema. Item Types are not graphic elements; rather, they represent a MicroStation capability for storing structured alpha-numeric data. Bentley Systems terminology for data stored in Item Types includes 'business data' and 'EC Schema data'.
The foundation of Item Types is the ECSchema
Item Types are meta data that define data types. In other words, a schema. Item Types were not available in versions of MicroStation prior to CONNECT.
Each Item Type has a name and a number of properties. Each property has a name and a data type (e.g. Text, Integer, Number) …
|Name||Human readable and machine readable. Visible in the UI|
|Internal Name||Machine-readable version of Name. Non-ASCII characters are translated to Unicode. Not normally visible in the UI|
Unfortunately, an Item Type property does not have a DisplayLabel, which most other ECSchema objects have …
|DisplayLabel||Human readable, not intended for machine consumption. Not available for Item Type properties|
Item Types are not graphic elements; rather, they represent a MicroStation capability for storing structured alpha-numeric data on an object. Item data can be attached to an element, DGN model or DGN file. Bentley Systems terminology for data stored in Item Types includes 'business data' and 'EC Schema data'.
Item Types provide a simplified way for users and applications to create, manage, and use EC data within DgnFiles.
An Item Type is an ECClass which supports a subset of the features available to ECClasses. In comparison to full-fledged ECClasses, Item Types:
Item Types are stored an Item Type Library, which is a similarly restricted ECSchema. In comparison to full-fledged ECSchemas, Item Type Libraries:
An Item Type Library is a resource, stored in a DGN file. Typically they are managed by defining the Item Type and its properties in a DGNLib, which is made available to all users who need to use that Item Type. A management dialog is provided by MicroStation for the end user …
Item Types are metadata. They become useful when they are "attached" to a host to produce an Item. An Item is an ECInstance of an Item Type ECClass.
From MicroStation CONNECT Update 15 Item Types permit Expressions in property definitions. An Expression can compose data from several sources.
From MicroStation CONNECT Update 10 Item Types are supported by MicroStation VBA.
MicroStation CONNECT Update 10 introduces the Picklist. A Picklist is a user-defined list of possible values for an Item property.
For example, suppose you want to annotate door cells with your Item Type. One property of your Item Type is door-type. You would like to restrict the value of the door-type property to internal door, internal fire door, external door and fire escape door. A Picklist enables you to constrain what the user can assign to your Item's door-type property.
MicroStation CONNECT Update 7 introduced the Edit Item Dialog..
MicroStation CONNECT introduced Reports. Reports is an analytic tool. It extracts alphanumeric data (business data) from your DGN file, model, elements or elsewhere. When Item Types are in use, Reports can extract Item instance data attached to your DGN model or elements.
Visit the reports page for more information, and to see an example of Reports in action.
Item Types is the term used in user documentation.
The MicroStationAPI and DgnPlatformNet APIs uses terms such as
VBA support for Item Types arrived with MicroStation CONNECT Update 10. See the following class descriptions in VBA help …
This article about AreaAnnotator CONNECT Edition™ shows how Item Types help obtain reports about area features in a DGN model.
I am indebted to Bentley Systems staff member Paul Connelly and to Be Communities MVP Jan Slegr. Both have contributed both factual information about Item Types and EC Schemas as well as their interpretation of how they can be used. They contribute enthusiastically to the MicroStation Programming Forum.
EC Schemas were introduced with MicroStation V8i and are continued in MicroStation CONNECT. They are the foundation of Item Types introduced with MicroStation CONNECT. You can read more about ECSchemas.
We don't discuss Item Sets here in any detail. We mention them because of the similarity in their name to Item Types. Item Sets were introduced with MicroStation V8i. Item Sets are unrelated to Item Types.