Automatic Property Promotion from the Stream
Topic Last Modified: 2006-06-12
The Exchange store provides special handling called property promotion for messages and Microsoft® Office documents when their content streams are saved. Typically, when you create an item in the Exchange store, no inherent relationship exists between the item's properties and its stream. With messages and Office documents, however, the item stream is automatically examined as it is being saved to the store, and property values are extracted from this stream and set for the item. Note, however, that this is a one-way action; if properties are subsequently set on the item, the stream is not automatically updated.
Property promotion is triggered in one of two ways: through file extensions, or through content type when using the WebDAV protocol. An Exchange store item saved with the one of the file name extensions listed and described in the following table has its stream content automatically examined for properties that are then promoted as fields for the item.
| File name extension | Description |
|---|---|
.eml |
Denotes an RFC 822-formatted message. Typically, messages are further formatted using the Multipurpose Internet Mail Extensions (MIME). The message stream is parsed, and the value of various mail header fields such as To: and From: are added ("promoted") to the item as properties. The DAV: Namespace for the item is also set appropriately; for example, urn:content-classes:message, and urn:content-classes:calendarmessage. |
.doc, .xls, .ppt and other Office extensions |
Results in the item being created with DAV: Namespace set to urn:content-classes:document. For Office documents that have standard extensions such as .doc, .xls, or .ppt, document properties available within the file's standard structured storage are added as item properties. |
For example, if you copy a message in a file called item.eml to the Exchange store using the file system, the Exchange store assumes that the file contains a message. It parses the message content stream and sets the various messaging-related fields for the item, such as the subject Field. Similarly, if you copy a Microsoft Word file to the Exchange store using the file system, the Exchange store examines the file's structured storage for standard Office properties, extracts the values, and automatically sets them for the item. For example, the Author document property value is used to set the Author Field for the item.
When you put items in the Exchange store using the WebDAV protocol, Office and message and application content types also trigger property promotion. For example, if you issue a PUT command and the content type of the body of the HTTP request is "message/rfc822", the Exchange store assumes that the inbound stream is an RFC 822 (and possibly MIME)-formatted stream, parses the stream, and promotes the various messaging-related headers to properties for the item. Similarly, the content type "application/msword" triggers the promotion of the document's structured storage properties to item properties.