Cortana能在每天清晨提供用户感兴趣的新闻报道摘要。Cortana同真人版的个人助理一样，允许用户设定“免打扰时间”。在此期间，电话和短信都静音，只有少数“重要”联系人能突破静音限制。Notebook功能使用户能调整Cortana对用户的了解，从而提供比Siri以及Google Now更精细的控制。Cortana似乎还颇具幽默感。假如你要求Cortana打开太空飞船的分离舱门，它会回答：戴夫，我恐怕办不到【戴夫是科幻电影《2001太空漫游》（2001: A Space Odyssey）中的人物】。
在许多方面，Cortana集Siri的语音搜索与谷歌Google Now的建议之大成于一身，基于用户所在的位置、时间、约会安排等数据进行搜索和建议。一部分早期评测称，Cortana之所以领先于苹果和谷歌的服务，主要是靠抄袭后两者各自最出色的功能。Cortana能调整手机的设置，比如是否连接到Wi-Fi等（Google Now就不行）。Cortana还能跟踪航班的状态（Siri只能给出相应网页）。
格里森表示，尽管苹果最早推出数字助理应用，但它如今突然沦为“追赶者”。“ 我们可以看到，谷歌和微软都在这个一往直前。很多人会说，Google Now和Cortana已经比Siri有用得多。苹果确实需要解决这个问题，否则就会落后，苹果可不习惯当掉队的人。”
Google Now直到2012年才亮相，但它迅速成为谷歌Android操作系统的关键功能。同Siri一样，Google Now能通过语音激活和控制，但与Siri 和Cortana不同的是，语音在Google Now中并没有占据中心地位。相反，谷歌强调Google Now能预测用户需要什么信息，何时需要信息。系统会扫描用户的近期搜索、常规旅行线路和电子邮件，以便获取用户可能想要马上看到的信息，比如用户亚马逊（Amazon）订单的处理状态、天气、用户最喜欢的球队的最新消息等。总之，Google Now不会等到用户开口再行动。
同Siri一样，Google Now用户能要求手机“发送电子邮件”或“半小时后叫我起床”，同时，Google Now增加了基于用户的搜索、活动以及其它数据给出的意见和推荐。比如，如果用户每周一晚上都在健身房锻炼，那么，Google Now很快就会知道每周一恰好在这个时候发出指示。Siri还做不到这一点，而Cortana正尝试模仿这项功能。
微软希望，Cortana内置的隐私控制功能能使它比无孔不入的Google Now对消费者更具吸引力。Notebook设置页面让用户设定Cortana能查看哪些信息，不能查看哪些信息，这一点十分关键。对此，IHS Global的格里森称：“也许Google Now与Cortana的关键差别在于，能否轻松控制显示什么信息，以及Cortana有权限查看什么应用。微软叫板谷歌的说辞就是：‘我们不会窥探您的隐私。’两家公司各自推出的个人数字助理服务也延续了两者长期以来的这种差别。”
尽管Siri、Cortana以及Google Now三者有许多类似的功能（比如创建约会、网上搜索等），三款服务其实存在根本性的区别：本质上，Siri为用户提供了另一种与自己手机以及手机中部分应用互动的方式。比如说，Siri善于理解自然语言、执行用户指示。Google Now和Cortana则增加了更为全面的一系列服务，同时还试图模仿真人版助手的功能。
The arrival of Cortana, Microsoft's (MSFT) digital assistant for its Windows Phone mobile operating system, means there's another decision to be made when it comes to buying a new smartphone: Who do you want running your life for you?
The newly unveiled Cortana app competes directly with Apple's Siri (AAPL) and Google Now (GOOG) for the chance to organize your appointments, contacts, travel arrangements, and all of the other minutiae of daily life. Microsoft calls Cortana the "truly personal digital assistant" -- a thinly veiled dig at its forerunners -- that analyzes how you use your phone to learn what topics you're interested in, when you're busy, and where you travel.
Cortana can deliver a summary of relevant news stories at the start of the day. Like a flesh-and-blood personal assistant, it also allows users to set up a "quiet time" where calls and texts are silenced as well as letting an "inner circle" of contacts break through those restrictions. The Notebook feature lets you tweak what the app knows about you, providing a more granular level of control than either Siri or Google Now. Cortana seems to have a sense of humor too. Tell it toopen the pod bay doors on your space ship, and she'll reply that she's afraid she can't do that, Dave (a sly reference to the sci-fi film 2001: A Space Odyssey).
In many ways, Cortana combines Siri's voice search with Google Now's suggestions, which are based on data like your location, the time, and your appointment calendar. Some early reviews say Cortana is a step ahead of Apple's and Google's services, mostly by copying the best features from each. Cortana can tweak a phone's settings like whether to connect to Wi-Fi. (Google Now can't.) Cortana can also track a flight's status. (Siri simply returns a web result.)
For now, only a test version of Cortana is available in the United States.
Cortana's competition: Siri
Siri started the digital assistant trend as an independent, stand-alone app before being acquired by Apple in 2010. A year later, Apple integrated Siri into iOS and started marketing the service as an "intelligent assistant that helps you get things done just by asking." Over time, Siri has become better at recognizing and interpreting commands while linking to more apps in Apple's ecosystem. What it doesn't have is all of the personalization and data collection found in Google Now and Cortana.
Siri plugs into your emails, contacts, and calendar, but it's not trying to find out everything about you. "In some ways, the approaches each company has taken in the space is a reflection on their heritage," says Tony Costa, a senior analyst for Forrester. "Google Now is much more like a search engine -- efficient, task focused, and trying to anticipate what you need. Apple Siri is much more of a natural language voice user interface. And Cortana a bit of a blend of the two approaches."
Currently, Apple does not have the breadth of services for Siri that Google and Microsoft have, and that's an area of concern for the company, according to Daniel Gleeson, an analyst for IHS Global. "Apple is relying much more on outside technology," he says. Voice recognition from Nuance and search results from Bing are just a couple of examples of help it's getting from others. "Google does all of that itself, while Microsoft has been researching voice recognition for over 20 years and has its own search engine as well."
Despite being first with a digital assistant app, Apple is suddenly playing catch-up, says Gleeson. "You can actually see Google and Microsoft moving ahead in this space," he says. "Many people will say that Google Now and Cortana are already much more useful than Siri. Apple does need to address that, otherwise it will fall behind, and that's not a position that Apple is used to being in."
Siri's voice control and personal data gathering were a first for mobile phones, but it's no longer enough. For a truly smooth and personalized experience, our digital assistants need to know as much about us as possible, and no one does that better than Google.
Cortana's competition: Google Now
Google Now didn't premiere until 2012, but it has quickly become a critical feature in the company's Android operating system. Like Siri, it can be activated and controlled by voice, but voice isn't front and center the same way it is in Siri or Cortana. Instead, Google emphasizes the app's ability to predict what information users need and when. Recent searches, regular travel routes, and email messages are all scanned for information the user might want to see straight away -- the delivery status of your Amazon order, the weather, the latest news about a favorite sports team. In short, it doesn't wait for you to ask.
While you can still talk to your phone to "send an email" or "wake me up in half an hour" as you can with Siri, Google Now adds suggestions and recommendations based on your searches, activities, and other data. Spend every Monday evening at the gym, for example, and it will soon learn to show directions on cue every Monday. This is something Siri doesn't yet have, and which Cortana is trying to copy.
Microsoft is hoping that the privacy controls it has built into Cortana will provide a more appealing product for consumers than the all-pervasive Google Now. The Notebook settings page that lets users set exactly where Cortana can and can't look is crucial. "Probably the key difference between Google Now and Cortana is that easy control over what is displayed and what apps Cortana has permissions to look into," says Gleeson, of IHS Global. "Microsoft positions itself against Google by saying, 'We don't look into your private stuff,' so this really continues that way of looking at it."
While the competing digital assistants offer a lot of similar functionality (creating appointments, searching the web), there are fundamental distinctions: At its core, Siri offers an alternative way of interacting with your phone and some of the apps on it. It's good at understanding natural language and acting on your instructions, for example. Google Now and Cortana add a more comprehensive collection of services and try to replicate the functions of a real-life assistant.