Microsoft introduced Cortana, the company's long-rumored answer to Siri, at its Build Developer Conference in San Francisco Wednesday.

The service, which Microsoft is billing as the first "true" personal digital assistant, is similar to Siri and Google Now, but emphasizes developing a relationship.

"Powered by Bing, Cortana is the only digital assistant that gets to know you, builds a relationship that you can trust, and gets better over time by asking questions based on your behavior and checking in with you before she assumes you’re interested in something," said Belifore in a blog post. "She detects and monitors the stuff you care about, looks out for you throughout the day, and helps filter out the noise so you can focus on what matters to you."

While we didn't have time to develop a relationship with Cortana in the time we spent with her this afternoon, we got to know her a little bit when we went hands-on with a Nokia phone running Windows Phone 8.1 at Build. Here's what we found:

Reminders

Like Siri and Google Now, Cortana is really good at setting reminders. But Cortana appeared to be a little better at discerning natural language then Siri. And she has more options when making them: Reminders can be tied to a time, a place or even a specific person.

Image: Mashable, Karissa Bell

For example, you can say "Cortana, next time I talk to Glen, remind me to ask him about his new house," and the next time you communicate with Glen — whether that's via a phone call, text, email, Skype or whatever — the reminder appears onscreen. Or, you can ask Cortana to remind you to buy eggs when you get to the grocery store.

Cortana's Notebook

In keeping with the personal assistant theme, Cortana comes with a "Cortana's Notebook" feature that contains all of the personalized information Cortana curates about you, and the services that fall in her purview. Notebook sections include interests, remind me, quiet hours, inner circle, places and music searches.

Image: Mashable, Karissa Bell

Interests keeps tabs on info relevant to your day-to-day life like traffic conditions for your commute home, local weather forecasts and stocks you track. Inner circle keeps track of the contacts most important to you and those contacts will still be able to reach you during specified "quiet hours," which is similar to Apple's "Do Not Disturb" feature.

Tracked interests are also reflected in Bing searches with relevant interests— stocks you follow, for example— highlighted when you're signed into Bing.

Chit-Chat

Dictating text messages worked well — Cortana seemed to have no problem picking out our words, even in a crowded room with a lot of ambient noise. Cortana did seem to have some trouble identifying punctuation marks though— an issue that also cropped up during the keynote when Microsoft's David Treadwell demoed Cortana's Twitter integration onstage and Cortana wrote out "hashtag" in place of the symbol.

When it came to general questions, Cortana was less consistent. Sports questions, for example, were hit or miss. While she was able to tell us when the next Edmonton Oilers game was, Cortana was not able to answer when the Stanley Cup would be played. Some of those issues will likely be ironed out though after the beta period ends later this year.

Image: Mashable, Karissa Bell

Cortana's sense of humor did come through throughout our demo. Asking about Siri yielded a slightly snarky response and a question about Bill Gates was answered similarly (Cortana "literally" cannot imagine life without Bill Gates.)

Microsoft said the beta version Cortana will roll out to U.S. users in the coming weeks and will expand to the U.K. and China in the second half of 2014.

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