BYTE.com > Tangled in the Threads > 2001 > November
Hybrid Storage Models
By Jon Udell
November 19, 2001
(Hybrid Storage Models
: Page 1 of 1 )
Mixing storage schemes creates opportunities, but poses dilemmas
When an application has to choose between a filesystem and a database,
there's never a right answer.
From the moment I first saw Groove, there
were two enhancements I craved. One was a bridge between the secure, instant-messaging-based
communication that flows within Groove shared spaces and the e-mail-based
messaging that flows all around them. The other was a bridge from the file-based
storage of conventional apps to the object-based storage of Groove apps.
It was impossible to see Groove's sketch app, for example, as anything
other than a stand-in for a "real" diagramming tool such as Visio. Could
such an app be redirected from the filesystem to Groove's XML object store?
The answer, I learned last week when Groove showed me its forthcoming
Office integration technology, is yes and no. Yes, you'll be able to collaborate
on a Word document that's synchronized across Groove shared spaces. But
no, Word's OLE-based storage model is not magically transposed into that
of the Groove object store — not yet, at least. According to Groove, the
issues are partly social and partly technical. On the social side of the
equation, live updates to a document that's synchronized across a shared
space can be confusing. So updates are batched from a master instance of
the document to the rest, and users negotiate who controls the master instance.
Technically, though, OLE structured storage — a "filesystem within a file"
— can yield superior results. Intercepting raw filesystem APIs isn't very
helpful, because while all the bytes pass through that interface, none
of the semantics do. Hooking the structured storage interface, though,
gives access to richer semantics. That's a technique that Groove already
exploits in order to integrate with some ActiveX components but, due to
the complexity of the task, not yet with Office apps.
Ultimately, of course, the standard filesystem wants to become a kind
of object database, to which applications can persist self-describing objects.
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