Opening Documents

Besides crawling resources, we should also be able to open them in their default viewer.

At first this may sound like a job for the DataAccessor, which after all has knowledge about how to load the stream from the physical source.

On second thought, I believe that for the opening of files you need some other service, parallel to DataAccessor, that is also scheme-specific and that takes care of opening the files. Reasons:

• DataAccessors actually retrieve the files/webpages/..., which is often not necessary for some DataObject openers. For example, for opening a local file you can instruct Windows to do just that. Similarly, a web page can be retrieved and shown by a web browser, there is no need for our codebase to retrieve the contents and feed it to the browser.

• There may be several alternative ways to open some type a resource. For example, the java.net JDIC project contains functionality for opening files and webpages, we at Aduna have written our own classes to do that, there may be customer-specific implementations, etc.