[Back to Blog](/blog) # Part References Overview

Andrii Morozov June 22, 2017 [\#mechanical](/blog/tag/mechanical) [\#geometry](/blog/tag/geometry)

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A part reference is geometry that is marked as a part. It is an annotative mechanical entity with special behavior that allows it to interact with a Bill of Materials (BOM) and to be included in other drawings or assemblies through external references.

#### Properties and Features

Part references are special entities with attributes that are used to mark parts in assemblies and populate part data to a Bill of Materials database. Below is an attached and detached part reference.

![part references](/files/inline-images/part%20references.png)Part references do not contain much data — a flag that shows whether it is detached and a data entry object that stores all part reference attributes (component properties).

![image3](/files/inline-images/image003_1.png)*Part reference component properties shown in OdaMfcApp example application*When part references are present in a drawing, there are also BomRow records in dictionaries (BomRow records also appear in a Bill of Materials for further processing)

and data entry objects with part reference data.

![image4](/files/inline-images/image004.png)*Part reference data object*A Bill of Materials counts the part references and components. Part reference attributes work like component properties for components. A referenced part could be included in another assembly or drawing, and a Bill of Materials or an external file could be attached to a selected part reference.

#### Examples

Example of how to extract data from a part reference:

```

OdDbObjectId dataEntryObjectId = pPartRef->dataEntryId();
```

Example of how to remove an attribute from a part reference:

```

OdError errStatus = pPartRef->removeAttribute("DESCRIPTION");
```

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