Document Property Promotion and Demotion
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Managing the metadata associated with your document is one of the most powerful advantages of storing your enterprise content in Windows SharePoint Services 3.0. However, synchronizing information between the document library level and the document is a challenge. Windows SharePoint Services provides the document parser infrastructure, which enables you to create and install custom document parsers that can parse your custom file types and update a document for changes made at the document library level, or update the document library with changes made at the document level. Using a document parser for your custom file types helps ensure that your document metadata is always current and synchronized between the document library and the document itself.
A document parser is a custom COM assembly that implements the Windows SharePoint Services 3.0 document parser interface, and does the following when invoked by Windows SharePoint Services 3.0:
Extracts document property values from a document of a certain file type, and passes those property values to Windows SharePoint Services for promotion to the document library property columns.
Receives document properties and then demotes those property values into the document itself.
This functionality enables users to edit document properties in the document itself, and enables automatic updating of the property values on the document library to reflect their changes. Users can similarly update property values at the document library level, and have those changes written back into the document automatically.
Windows SharePoint Services selects the document parser to invoke based on the file type of the document to be parsed. A given document parser can be associated with multiple file types, but you can associate a given file type with only one parser.
In addition, Windows SharePoint Services includes a built-in XML document parser you can use to promote and demote the properties included in your XML documents. Your XML files can adhere to any schema you choose. For the XML parser to promote and demote document properties, the XML file must be assigned a content type that specifies where each document property is located in the document, and which content type column that property maps to. If your XML file meets these requirements, Windows SharePoint Services automatically invokes the built-in XML parser whenever document property promotion or demotion is required.