How do I create a domain model related to managing confidential documents?

I am working on a desktop application that specifically deals with the application of read and write permissions for confidential documents (MS Word).

Multiple permissions can be defined for a document. For example:

• user X can read document D1 between start_date and end_date
• user Y can read and edit document D1 at any time

In addition, the permission set for the document must be available for display in the user interface.

In addition, the document can be signed (with a certificate) by the current user of the application (the author of the documents).

Lately (after you have objects with less behavior and some line of business / applications) I came up with this:

interface IConfidentialDocument {
    void AddPermission(Permissions permission);
    BunchOfPermissions Permissions { get; } // all defined permissions
    void Sign(User currentUser);
    ... other operations (like ShareToUsers, SendViaEmail)
    string Path { get; }
}

class Permission {
    User User { get; private set; }
    PermissionType Type { get; private set; } // Read, Write, Full etc.
    ... other members (for time bounds etc.)
}

      

        
        
        
      

    

The problem is that IConfidentialDocument has to be implemented using the Word Interop library . I couldn't discern a good way to wrap the Word Interop functionality and hide my corrupt design in a simpler model as shown above.

I was thinking about embedding IConfidentialDocument as WordDocument, which delegates this work to Microsoft.Office.Interop.Word.Document. The latter will be passed in the constructor of the WordDocument. This will create ConfidentialDocumentFactory.Create (string). The specific factory will depend on Microsoft.Office.Interop.Word.Application etc.

• Is there a DDD way to work with such a domain?
• (How) should I define an anti-corruption layer over / against Word Interop?
• Should I make the domain anemic and define services like DocumentsSigningService, PermissionsApplyingService? - actually, this is what I have now - it works, but ...
• Is it possible to use double dispatch?
  • document.SignVia (signingService)
  • document.ApplyPermissionsVia (permissionsService, bunchOfPermissions)

Business is actually a little more complicated. It also includes sending documents to their authorized users (via email), etc. What I've done so far relies on a set of business services and application services to do most of the logic - the ConfidentialDocument thus has nothing to do with behavior. But as I said, I am looking for the best design.

Any idea is appreciated :)

Thank!

Some links (not enough reputation to add links):

• How not to inject services in essence (thinkbeforecoding)
• Best Domain Event Model (lostechies)