SEATTLE—At its annual Build developer conference, Microsoft took the wraps off the next major Windows 10 version, the Fall Creators Update, and announced some of its new features.

One of these new features, Timeline, is going to be good when you're using Windows 10—but even better when you're not. Timeline tracks what you're doing—which documents you have in which apps, which e-mails you're writing, what Web pages you have open, that kind of thing—and lets you retrieve that information later.

On Windows, the Timeline information is displayed in the task switcher. Press the taskbar button (or, we'd hope, Win-Tab) and Windows will continue to show your currently open applications. But you can now scroll that view to bring historic applications and documents into view.

Where this really comes into its own is when Cortana is added into the mix. The Cortana element is called "Pick Up Where I Left Off," and it allows a similar kind of restoration of what you're doing. PUWILO is available in Windows, but, like Cortana, is also available on iOS and Android. This means that for applications that support it, you'll be able to stop what you're doing on one machine—writing an e-mail, say—and resume that task on an iPhone.

On Windows and Android, Cortana will even install the necessary app for you if it's not already present.

Behind the scenes, this is powered by the Microsoft Graph. Microsoft has been talking about the Graph for a number of years, and in truth, it has often felt quite abstract. It has its origins in Office 365; the Graph was initially a representation of user and group data that was stored in Azure Active Directory. New elements have been added over time; the Graph also represents, for example, documents and files, so you can find out who has been working on what files and when.

Yesterday, Microsoft said that it was adding device information to the Graph. Now, the Graph doesn't merely represent that you, say, started writing an e-mail—it represents that you started writing an e-mail on your PC, and hence that it's meaningful and relevant to offer to migrate that same activity to your phone.

As the Graph has added more kinds of data, more developers have started using its APIs, though thus far they've tended to focus on Office 365 users in the enterprise. Microsoft Accounts offer a subset of the capabilities, though they still support the same style of programmatic access. PUWILO is perhaps the first big use case where developers of consumer apps will have good reason to use Graph. As well as exposing their data to the Graph, apps can also customize their appearance of how their activities are presented, both on phones and on PCs.

With this cloud dependence, it's not entirely surprising that using Timeline and PUWILO will need either a Microsoft Account or an Office 365 account.

Timeline and PUWILO are also being used to power a cross-device, history-saving Clipboard. Copy-and-paste will work between machines (on phones it will use the SwiftKey keyboard rather than Cortana), and it will offer history; you'll be able to retrieve older clipboard entries, so even if you overwrite the clipboard by accident, it's not a disaster.

Apple's Handoff offers a similar capability for moving activities from one machine to another (at least when they're in close proximity), and Apple also has a Universal Clipboard as part of its broader Continuity range of features. But these only work on Apple hardware. If you use an iPhone and also Windows, or a Mac and also Android, none of the Handoff or Continuity features are available.

Microsoft's approach, by contrast, is cross-platform. This is, of course, in no small part due to Windows' near-total absence on phones, but the net result is a system that can potentially be used by far more people, much more of the time.

Listing image by Microsoft