Engineering Hybrid Documents

The last entry discussed CAD file viewers that enable any user to view the CAD model data created from applications in the original file format.

Another twist when working with CAD documents is that not only is the underlying data complex but often the ‘document’ itself is not a single file, but a packet of files. For example, a CAD document might consist of vector graphic layers superimposed on top of a TIFF image.  The TIFF image is stored in one file and the other layer components may be in one or multiple files.
These multi-file CAD model documents are often referred to as hybrid documents.

The document repository manages the document relationships and understands which file of the hybrid document packet is the primary CAD drawing and which files are components that are referenced by the primary file.

But hybrid documents and thin-client applications can present special problems. Retrieving and managing hybrid documents from standard web-based storage applications can be painful. Web browsers understand MIME types, but they don’t know about the concept of hybrid documents.  Users expect to be able to single-click on a document reference returned from a document repository search and automatically launch and display the document in the view application.  But to launch and view a hybrid document requires that all the component files of the hybrid document be first downloaded to the user’s machine and located in the same directory.

When the browser communicates with the web server it can only receive a single file in response to a server request.  And for security reasons there is no way to specify where the file will be downloaded on the client machine.  So getting all the files onto the client machine, having them located in the same directory, and then launching the view application can be a challenge in a standard browser.

Formtek solves the problem by including a browser plugin with its web application.  The plugin loads onto the user machine a single time, and thereafter the browser client can efficiently communicate with the server to download all component files and then launch the view application.  The whole process is initiated with a single click and the whole process works like the user would expect.