Signs to Cairo

Cairo, Microsoft's object-oriented successor to Windows NT, will begin beta testing in early 1996 for release in 1997. Although Microsoft is not revealing the full details of Cairo yet, there are enough clues within current Microsoft OSes to yield a good idea of how it might work.

The OLE 2.0 embedding model that integrates the components of Microsoft Office already contains the seeds of a future object-oriented file store in its structured-storage technology. Word DOC files, Excel XLS files, and PowerPoint MPP files share a common internal docfile format. The screen "Is There a Docfile in the House? " shows the internal structure of a Word document that's embedded in a PowerPoint presentation. The internal stream struct ure of the combined file has taken on a tree structure, just like a disk directory, reflecting the embedding of its components.

If you open the document in PowerPoint and double-click on the embedded Word document, PowerPoint finds out what application owns it from the Windows Registry. The OLE engine then negotiates between PowerPoint and Word, and PowerPoint's toolbar morphs into Word's formatting toolbar so you can edit the Word document.

Now peek into the future. The top level will no longer be a separate application such as PowerPoint, but the Cairo desktop itself. The streams comprising the compound document will no longer be inside a DOS file allocation table (FAT) file system. Cairo's Object File System (OFS) makes the whole hard disk a single huge docfile that exposes its internal objects to the user.

The groundwork for a distributed object store is present, too, in the shape of Microsoft Exchange Server (MXS) and the OLE-automatable Jet 3 database engine. If yo u drop any structured-storage object (e.g., a Word file) into an Exchange folder, any custom properties you've defined become available as values to sort on or filter by. MSX is based on the ISO X.400 message transport and X.500 directory services, which, combined with Cairo's OFS, should be able to locate remote objects across a network. By the time Cairo is released, MXS might be absorbed into the OS.

In short, the migration from Windows to Cairo could be less drastic than expected, given that all your Office data files are already in a structured format that Cairo will understand. The much greater challenge for Microsoft is how to decompose monolithic applications such as Excel into collections of discrete lightweight objects. The OLE automation interface already requires that applications make some of their internal organs visible as objects, but that is not at all the same as delivering them as separate pieces. It could turn out that Microsoft will encounter stiff competition from Visual Basic cust om control/OLE custom control (VBX/OCX) vendors such as Sheridan and MicroHelp, who have a head start because their products are already in bits.

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Is There a Docfile in the House?

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The structured storage of Microsoft's docfile format represents a collection of objects just waiting to be set free. Word, Excel, and PowerPoint files all have the same internal structure, so embedding one in the other is easy.

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Name's No Longer the Thing

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Custom properties in the main Office applications point the way to an object-retrieval system in which filenames cease to be of importance.