Exploring Cairo

No doubt, the massed choirs of Windows 95 users are singing from the rooftops, because Office 95 under Windows 95 allows long filenames. They think this is going to be of so much more use to them; 8+3 was a dreadful limitation, even 15 years ago.

But what narrow thinking! Going from an 8+3-character filename to a 256-character version of the same thing is progress only in as much as it's a move from disastrous to meagre on the usefulness scale.

Let's look at it another way. If you were to take all the documents on your desktop computer-or, better still, your corporate LAN-and put them into one directory, would 256-character filenames really be enough? No, of course not! You'd still want the filtering, sorting, and collating facilities offered by subdirectories. But as soon as you put documents into subdirectories, you're scattering your data into the unknown far reaches of your hard disks, never to be seen again in a hurry, because the retrieval tools are so weak and rigid.

Indeed, to look at it from still another perspective, think about a database design. You would definitely want a unique key-or a unique combination of keys-on a database entry. Allowing multiple entries to have the same master key is a recipe for disaster. Suggesting that a database manager scatter data randomly across multiple tables so you can sort and query them more easily would undoubtedly end in a major argument. The database manager would argue that all you need is to add another field or two to each record to uniquely define it.

Now spin that mindset into a disk-filing system, and you can see how even a 256-character filename strategy is pathetically weak. You need unique document identifiers and multiple "database-alike identity fields" to categorize your data. Hence, even 256-character filenames are a largely useless solution for the late '90s, especially since gigabytes of disk space storing hundreds of thousands of files cost mere hundreds of dollars today.

Not surprisingly, Microsoft has a strategy in place to sort this mess out. It's called Cairo. For what seems like an eternity, Microsoft has been proclaiming, "We are all on the road to Cairo." Indeed, this future, still unseen release of Windows NT has been coming for so long that it has gained almost mythical status. Private discussions with Microsoft have clearly indicated that Cairo hasn't vanished, that work has been steadily progressing over the last couple of years, and that 1996 is going to be the year of the grand roll-out of Cairo-at least initially-in beta form.

So, I thought it would be useful to explore the current state of play to see where this mythical Cairo technology is coming from. Hopefully, by the end of this journey from Office to Cairo, you'll agree that large components of Cairo have been sitting on your desktop in full view for nearly two years.

Of course, there are many facets to a large project like Cairo. Although I can't speculate now about how all of them will work, one clear thread is worth pursuing: how the object-storage system works today-how it might well be developed for Cairo and how it will help solve our data storage and retrieval problems.

Office and Storage
The questions must have crossed your mind: When you embed an Excel worksheet in a Word document and then save the document, how does Word "know" how to store the Excel file? Where is the Excel file stored? And if it's stored in the Word file, is it converted to a Word table?

Since you can reload the Word file and then double-click on the Excel file to bring up an in-place editing instance of Excel with all the editing and formatting capabilities of Excel supported, then the Excel worksheet must be stored natively within the Word document. These functions simply wouldn't be possible if Word converted the Excel table to a Word table.

If you embed a different kind of document, such as a PowerPoint slide, the same logic applies: The native PowerPoint presentation is stored within the Word file. Indeed, Word has no native concept of a presentation so it's hard to conceive of how such a Word-centric conversion could work.

Normally, this is the stuff of private data formats. It would immediately suggest that Microsoft had written some private Office data format that could store any data file from any Office application. That would make complete sense, except for one thing: You can embed any data file from any Object Linking and Embedding (OLE) 2-supporting application in a Word file. The implication is clear. This "embed and store" mechanism can't be relying on private formats, because you can embed objects from applications that have no connection with Microsoft. Thus, adding a Visio drawing is no more difficult than bringing in an Excel worksheet.

There must be a standardized, open-storage, container-and-content model at work here, something that any vendor can tap into. There is! It's called Structured Storage, and it's been around since the release of OLE 2.0.

Structured Storage is fascinating for many reasons, not the least of which is that so few people have actually looked carefully at how it works. Fortunately, Microsoft has tools that let you look inside a Structured Storage file to see what's going on. The best tool to use is DFVIEW.EXE, which is a Structured Storage DocFile viewer supplied with Microsoft Developers Network (MSDN) Level 2. In addition, there's a good book on OLE 2 by Kraig Brockschmidt entitled Inside OLE, Second Edition from Microsoft Press. The chapter "Structured Storage and Compound Files" is detailed and informative, although as a whole the book is a deeply technical reference that warrants several readings.

To illustrate how Structured Storage works, let's look at a basic Word 7 file. I created a new Word document, put two words into it, and saved it to C:\tempword1.doc. I then loaded this file into DFView (see Screen 1).

You can see that it shows a hierarchical layout with the top level being the storage file itself. This is the file on the disk. At the next level, there are four streams of data: The first is called Comp-Obj for Compound Object; the second is called WordDocument and contains the actual Word document data. The third and fourth are a SummaryInformation stream and a DocumentSummaryInformation stream. These last two contain summary information tags like Author, Date Created, Size, Last Printed, and so on. Each of these four streams is a separate data stream in the Structured Storage file.

Having closed the DFView display of the file and reopened it in Word 7, I inserted a simple two-cell, two-row Excel 7 worksheet into the Word file, using the Excel button provided on the Word button bars. Then, I resaved word1.doc and reopened it in DFView (see Screen 2).

Things are definitely becoming interesting. There are still the same four Word object streams in place, but there is also a new stream, called ObjectPool. If you open the ObjectPool stream, you'll see another storage object with an obscure numbered label. If you then open this object, you'll see what looks like another complete document stream, just like the one at the root of the tree. There are the same CompObj, SummaryInformation, and DocumentSummaryInformation streams. But the WordDocument stream has been replaced by a Book stream. This contains the Excel Book worksheet information-the Excel worksheet object that was inserted into the Word document. In addition, there are a couple of extra streams here to render the object when its container is running. In other words, when you are editing the Word document, you want to see a visible representation of the contents of the Excel object, even though Excel isn't running at that point.

Let's take this one step further and put a WordArt object inside the Excel object, which is inside the Word object. Phew, my head is spinning. How about yours?

Screen 3 shows what's happening-I have in-place activated the Excel object, and then inserted the WordArt 2 object into the Excel object. You can't currently in-place edit more than one level deep-OLE 2 doesn't support multiple nesting of all the negotiation that goes on between the various applications. So, although Word will negotiate with Excel to bring up the Excel "look and feel" in the Word framework, it can't negotiate with WordArt to go two levels deep.

Let's look at this triple-layer sandwich using DFView to see the result of this multiple embedding (see Screen 4). Not surprisingly, there is a WordArt object stored inside the Excel object, which is stored inside the Word object.

What Does It Mean?
OLE 2 containers can contain objects of completely foreign formats, and as far as the container is concerned, the contents of the embedded object are opaque. Word doesn't know-or need to know-how Excel stores its internal data. Nor does Excel need to know how WordArt stores its data. They simply need to know how to contain them, and this is defined in the Structured Storage standard.

Although I only inserted one object into another, there's no limit on the number of objects you can insert in parallel. For example, I could have put two Excel worksheets, each containing different objects, into the Word document. The resulting tree structure is easy to imagine. Just think of Structured Storage as an object filing system. The similarities between what DFView has revealed and what's in a standard directory/subdirectory/file structure are plain.

Into a Binder
Office 95 includes a new application called Binder. It allows you to take Office documents and put them into a composite file together. Binder embodies the concept of putting the contents of a folder (or a directory) into a single object. You can then switch among the various objects in a binder, and Binder does all the in-place editing activation necessary using OLE 2.

How does it work? Binder uses Structured Storage for its file store. For example, I created a new Binder object and dragged and dropped the composite Word-document object into the binder. Then I created a new Excel object in the binder (see Screen 5). Look carefully at this structure. It has two main Binder objects, called 1 and 2. The first is the Word document with the Excel and WordArt embedded objects. The second is the Excel sheet I dropped into the binder. Finally, look at the standard Binder type at the top level, together with its SummaryInformation and DocumentSummaryInformation streams.

Are you starting to see a pattern? The reality is: With Structured Storage, Microsoft has been running file-sized full-blown object filing systems. Indeed, a Structured Storage file could be regarded as a full-blown storage engine in itself-a sort of prototypical Cairo Object Filing System! This is why, when some corporate IT managers call Microsoft's ability to create an Object Filing System into question, I point out that there are already hundreds of millions of documents out there that use Structured Storage and they work just fine, thank you. Microsoft has been using this storage engine in Office ever since version 4.x.

Binder is important, because it's the first application from Microsoft that works "one layer out" from the main applications. Binder is a container of Word, Excel, PowerPoint, etc. objects. As such, it is effectively an active container surface into which you can pour data objects to work on them. Imagine the Windows 95 shell allowing direct Binder-type operations, and you can see how a Cairo active desktop might well be a container system itself.

Near Future
Now, let's make a leap sideways to a forthcoming piece of software from Microsoft-Exchange Server (see "Groupware: The PC Team Sport" on page 33). As you may know, Exchange Server replaces Microsoft Mail and brings, at last, a full Messaging Applications Programming Interface (MAPI) to the desktop in a proper client/server email system.

However, Exchange Server has more important tricks up its sleeve. It has Public Folders, which automatically replicate data among Exchange Server engines around your enterprise. If you wish, you can use Public Folders to store email. But it's far more potent to drop Structured Storage files in them. Just fire up File Manager (or Explorer, if you're running the Windows 95 shell), and drag and drop a pile of Word, Excel, and PowerPoint documents into a Public Folder. Exchange Server swallows up the files and stores them within its active storage engine (see Screen 6).

Now the magic can really start. Look carefully at the columns in the Folder view-no great surprise. There are columns detailing From, Subject, Received, and Size. However, after a little fiddling with the Folder columns settings, I've made dramatic changes to the information shown (see Screen 7). Exchange Server is "surfacing" the properties applied to each object-in this case, Manager, Client, Value, and Authorised. Manager is a standard property held in the Summary tab of the file Properties window in each Office application. The other three are custom properties that I added to each object (see Screen 8).

Since Exchange Server is storing these documents in an active repository, they can be replicated and distributed around the organization. I can attach full security rights to the Folder and its contents. But most important, I have completely removed the importance of the filename from the object. No longer do I need to refer to an object only by its filename.

Although Windows 95 and NT have full 256-character filenames for files, that's far from enough. Length is not the issue; the granularity and the number of attributes that can be attached to an object is the real key. For example, if I want to mark all the files belonging to Project X, I don't want to have to put Project X into each filename. It would be far better to have a Project Name attribute attached to each object. And Structured Storage, Office, and Exchange Server allow me to do this. These tags are stored in the SummaryInformation and DocumentSummaryInformation streams. Each Structured Storage Office-compatible application has these streams, even for subobjects in a compound embedded object.

Power Exchange Operation
For anyone interested in a really powerful document management system, Screen 9 should raise the hair on the back of your neck. Exchange Server has, at my request, sorted and collated the objects in this Public Folder by the Manager property and presented the results in a tree diagram. You can collate up to four levels deep, so there's no problem displaying a tree of customers, where each customer's information is sorted by "Invoice Paid? Yes/No" and then by date, or something like that.

If you attended the December 1993 Microsoft Windows "Chicago" Professional Developers Conference in Anaheim, California, you'll probably remember the awe-inspiring demonstration of Cairo given on the first day. The sorting and collating I've described was demonstrated as a Cairo feature.

On to Cairo
At this point, I must make it clear that I'm dropping out of the realm of the known and into the realm of informed speculation. However, what I'm describing is logical and consistent with the above.

Exchange Server uses a modified Jet database engine for its storage. It's known that Cairo has a native Object Filing System (OFS) based on the NT File System (NTFS) disk format. NTFS is a very flexible storage engine and has many features similar to those of a transactional database engine. For our purposes, the most important feature is that each file object can have an unlimited number of properties attached to it. (I don't want to go into too much detail on NTFS. Suffice it to say, Helen Custer's Inside the Windows NT File System from Microsoft Press is required reading.)

Reading Custer's book and matching it up to the Exchange Server and Structured Storage information, coupled with discussions with senior Microsofties, leads me to believe that NTFS will be extended under Cairo. It will appear to be backwardly compatible with the current NTFS, but it will have a whole new set of active processes running on top of it. In other words, the Jet database-style engine of Exchange Server will be replaced by the Cairo OFS, based on NTFS.

NTFS-based OFS has everything you need: It can hierarchically store objects; it can index on properties; it can store Custom properties; and it is robust and a proper filing system. For example, when you save a Word file, it talks to the local OLE storage engine running on your machine. This engine creates the Structured Storage disk file, and Word pours its contents into the file. The OLE libraries manage all the file handling.

When you store documents in Exchange Server, Word talks to the OLE storage engine which talks to Exchange. Word basically pours its contents into the Exchange Server engine, again via the OLE libraries. No major changes were necessary to allow Word to do that. In the Cairo future, the OLE libraries will talk to the Cairo OFS store, and Word will pour its data into that instead.

What more will Cairo uncover? Exchange Server only sees the outer layer of the onion. It doesn't look inside the Structured Storage object. It pulls out the SummaryInformation, but embedded objects within the document are still hidden.

Cairo will actually break a Structured Storage document into its component parts. This will allow it to display all the components in the document and to show all the standard and custom Summary tags for each object too. Remember, each object in a compound document has its own set of tags.

This revealed structure will enable multi-user document creation and editing. Since Cairo, by virtue of its NTFS host, will be able to do database-style record locking on each individual component of the Structured Storage document, it will be possible, for example, for several users to work on different parts of a compound report, enabling much finer document indexing and retrieval processes. After all, a list of "hot words" on each object is just another set of custom property tags that can be individually indexed, sorted, and collated in the Cairo OFS storage engine.

The Path Is Clear
By focusing on how Structured Storage works and the benefits it brings, you can see the direction that Microsoft is taking and how Exchange Server is a big step along that road. Ignore all the email parts of Exchange Server, and look closely-it's really Cairo 0.75.

It's also important to realize that Cairo won't be just a server-side solution. To operate at its best, it will need client-side applications that understand both OLE and Structured Storage. It's not surprising that Microsoft's own Office product has been doing precisely this for the past two years.

I'm told that there will be a clean and simple upgrade path from Exchange Server to Cairo itself, when Cairo is ready to ship. Indeed, Exchange Server 2 will probably be fully Cairo-hosted. This is a sweet victory for Cairo, because all the indications are that Exchange Server 1 was never really supposed to happen. According to all the time scales and published plans, we should be running on full Cairo by now.

The delays in Cairo-and in getting NT 3.5 out the door-mean that Microsoft had no choice but to put together an interim solution. Exchange Server 1 is that solution. And although it may be an interim solution, it offers some extremely interesting technologies for the future that you can put to work today. The exodus from the filename starts now.

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