I'm wrapping up a week in the beautiful French Riviera at the European version of Microsoft Exchange and Collaboration Solutions Conference (MEC) 2000 in Nice. (Now I can finally get a vacation!) During the week, a subset of MEC Dallas sessions repeated in Nice. One new topic this year was the local store.
The local store is a significant new technology that I believe will be particularly meaningful to the client side and developers in the Exchange and Outlook environment. You can think of the local store in terms of the current offline store (.ost) file on steroids. Many of us use an .ost file to enable offline use of our Outlook client. As I travel, I rely heavily on the offline store so I can continue working in Outlook (email, calendaring) even though I'm not connected to my Exchange server. When I connect (via RAS or otherwise), I simply synchronize my offline store with my mailbox on the server. This processes all incoming and outgoing mail and brings my local offline copy in synch with the server. In the current Outlook version, the Outlook client accomplishes this synchronization process via the Messaging API (MAPI) protocol. Although feature rich, MAPI has many shortcomings when you use it for this purpose. Also, the current implementation of the offline store doesn't provide integrity protection, and many users find themselves with broken OSTs. Though functional, the offline store has limitations and isn't really extensible by application developers.
The idea behind the local store technology that will be available with the next version of Microsoft Office (Office version 10—Microsoft released version 9 in Office 2000) is to implement a mechanism whereby the Outlook client provides a local storage container that enables complete offline access without the limitations of OSTs in Outlook 2000 and previous versions. The local store is not just a new file type or protocol for Outlook. It's an actual local database engine (using Exchange's Extensible Storage Engine—ESE—technology) running on the client. Also, the local store concept extends beyond the Outlook application and is available to all Office applications directly. This lets Office users work regardless whether they're connected to a server.
Another important aspect was to move away from MAPI dependence. Although the initial version of the local store will use MAPI between local applications and the local store, communications between the local store and the server will be via HTTP-DAV. After Microsoft deploys Outlook 10 and clients are using local store technology, the effect on the client protocol workload profile for a typical Exchange server will be significant. Eventually, HTTP communications will replace the intensive and high overhead we see with MAPI today. This move away from MAPI (to the server) also has ramifications for application developers because they'll need to look at how client applications work in this environment.
Although still in the future, the local store will be an important technology that affects both the client and the server side of our Exchange deployments. As you add technologies to your "To Be Researched" list, don't forget this key new development from Microsoft.