Question:  iOS 6 was announced at what conference also referred to as "dub-dub"?

full_context: Document 1: IOS 7: iOS 7 is the seventh major release of the iOS mobile operating system developed by Apple Inc., being the successor to iOS 6. It was announced at the company's Worldwide Developers Conference on June 10, 2013, and was released on September 18, 2013. It was succeeded by iOS 8 on September 17, 2014.
Document 2: Apple A6: The Apple A6 is a 32-bit package on package (PoP) system on a chip (SoC) designed by Apple Inc. that was introduced on September 12, 2012 at the launch of the iPhone 5. Apple states that it is up to twice as fast and has up to twice the graphics power compared with its predecessor, the Apple A5.
Document 3: Apple Inc.: Apple Inc. is an American multinational technology company headquartered in Cupertino, California that designs, develops, and sells consumer electronics, computer software, and online services. The company's hardware products include the iPhone smartphone, the iPad tablet computer, the Mac personal computer, the iPod portable media player, the Apple Watch smartwatch, the Apple TV digital media player, and the HomePod smart speaker. Apple's consumer software includes the macOS and iOS operating systems, the iTunes media player, the Safari web browser, and the iLife and iWork creativity and productivity suites. Its online services include the iTunes Store, the iOS App Store and Mac App Store, Apple Music, and iCloud.
Document 4: IOS: iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that presently powers many of the company's mobile devices, including the iPhone, iPad, and iPod Touch. It is the second most popular mobile operating system globally after Android.
Document 5: Digitalk: Digitalk is an annual two-days technology conference, organized by the Bulgarian business newspaper Capital weekly. Digitalk provides a place for discussion between creative professionals, investors, entrepreneurs, and marketing executives on the future of the web. Speakers cover topics such as mobile marketing, online advertising, commerce, brand storytelling, and entrepreneurship. The first conference was held at the Ivan Vazov National Theatre in Sofia, Bulgaria on September 26, 2011. Its topics addressed the influence of mobile technologies on business and society. Past speakers include Matt Mullenweg, Horace Dediu, Felix Salmon, James McKelvey, Sasha Bezuhanova, and others. The 2011 conference drew more than 700 people from all over Southeastern Europe.
Document 6: IPad (4th generation): The fourth-generation iPad (marketed as iPad with Retina display, colloquially referred to as the iPad 4) is a tablet computer produced and marketed by Apple Inc. Compared to its predecessor, the third-generation iPad, the fourth-generation iPad maintained the Retina Display but featured new and upgraded components such as the Apple A6X chip and the Lightning connector, which was introduced on September 12, 2012. It shipped with iOS 6.0, which provides a platform for audio-visual media, including electronic books, periodicals, films, music, computer games, presentations and web content. Like the iPad 2 and the third-generation iPad, it has been supported by five major iOS releases, in this case iOS 6, 7, 8, 9, and 10. iOS 11, which was released on 19 September 2017, will not have support for the fourth-generation iPad because of hardware limitations.
Document 7: Apple A9: The Apple A9 is a 64-bit ARM-based system-on-chip (SoC), designed by Apple Inc. Manufactured for Apple by both TSMC and Samsung, it first appeared in the iPhone 6S and 6S Plus which were introduced on September 9, 2015. Apple stated that it had 70% more CPU performance and 90% more graphics performance compared to its predecessor, the Apple A8, and was one of the most powerful and energy-efficient mobile chips on the market then along with the Samsung Exynos 8890 and Qualcomm Snapdragon 820.
Document 8: IOS 6: iOS 6 is the sixth major release of the iOS mobile operating system developed by Apple Inc, being the successor to iOS 5. It was announced at the company's Worldwide Developers Conference on June 11, 2012, and was released on September 19, 2012. It was succeeded by iOS 7 on September 18, 2013.
Document 9: IOS 5: iOS 5 is the fifth major release of the iOS mobile operating system developed by Apple Inc., being the successor to iOS 4. It was announced at the company's Worldwide Developers Conference on June 6, 2011, and was released on October 12, 2011. It was succeeded by iOS 6 on September 19, 2012.
Document 10: IOS version history: iOS is a mobile operating system, developed by Apple Inc. for iPhone, iPad, and iPod Touch. Updates for iOS are released through the iTunes software, and, since iOS 5, via over-the-air software updates. With the announcement of iOS 5.0 on June 6, 2011, a USB connection to iTunes was no longer needed to activate iOS devices; data synchronization can happen automatically and wirelessly through Apple's iCloud service. Major new iOS releases are announced yearly during the Apple Worldwide Developers Conference (WWDC), and are usually released in September of the same year, usually coinciding with the release of new iPhone models. The current stable release is iOS 11.0.1.
Document 11: Apple Worldwide Developers Conference: The Apple Worldwide Developers Conference (WWDC, also referred to as "dub-dub") is a conference held annually in California by Apple Inc. The event is used by Apple to showcase its new software and technologies for software developers. Attendees can participate in hands-on labs with Apple engineers, and in-depth sessions covering a wide variety of topics. WWDC began in 1983 in Monterey, California. Until 2007, the number of attendees varied between 2,000 and 4,200; however, during WWDC 2007, Steve Jobs noted that there were more than 5,000 attendees. The WWDC events held from 2008 to 2015 were capped, and sold out at 5,000 attendees (5,200 including special attendees).
Document 12: Apple Music Festival: The Apple Music Festival (formerly known as the iTunes Festival) was a music concert series held by Apple, Inc. inaugurated in 2007. Free tickets were given to Apple Music, iTunes and DICE users who lived in the United Kingdom, through localized prize draws. Performances were streamed live and available to view afterwards, free of charge, for Apple Music members on their Apple TV, iPhone, iPad, iPod touch, Mac, PC, and Android phones. In London, the Apple Music Festival had become an annual music festival which takes place in September at The Roundhouse art centre in Camden Town. The series made its United States debut with five days of free performances at the Moody Theater in March 2014, alongside the South by Southwest (SXSW) music showcase in Austin, Texas. In August 2015, the iTunes Festival was renamed as the Apple Music Festival. After a 10 year run, Apple confirmed to Music Business Worldwide that it will no longer host any music festivals.
Document 13: Apple A6X: The Apple A6X is a 32-bit system-on-a-chip (SoC) designed by Apple Inc., introduced at the launch of the fourth generation iPad on October 23, 2012. It is a high-performance variant of the Apple A6. Apple claims the A6X has twice the CPU performance and up to twice the graphics performance of its predecessor, the Apple A5X.
Document 14: DEF CON: DEF CON (also written as DEFCON, Defcon, or DC) is one of the world's largest hacker conventions, held annually in Las Vegas, Nevada, with the first DEF CON taking place in June 1993. Many of the attendees at DEF CON include computer security professionals, journalists, lawyers, federal government employees, security researchers, students, and hackers with a general interest in software, computer architecture, phone phreaking, hardware modification, and anything else that can be "hacked." The event consists of several tracks of speakers about computer- and hacking-related subjects, as well as social events Wargames and contests in everything from creating the longest Wi-Fi connection (aircrack-ng) and hacking computer systems to who can most effectively cool a beer in the Nevada heat.
Document 15: Singularity Summit: The Singularity Summit is the annual conference of the Machine Intelligence Research Institute. It was started in 2006 at Stanford University by Ray Kurzweil, Eliezer Yudkowsky, and Peter Thiel, and the subsequent summits in 2007, 2008, 2009, 2010, and 2011 have been held in San Francisco, San Jose, New York City, San Francisco, and New York, respectively. Some speakers have included Sebastian Thrun, Rodney Brooks, Barney Pell, Marshall Brain, Justin Rattner, Peter Diamandis, Stephen Wolfram, Gregory Benford, Robin Hanson, Anders Sandberg, Juergen Schmidhuber, Aubrey de Grey, Max Tegmark, and Michael Shermer.
ground_truth: Apple Worldwide Developers Conference