of the survey criteria. Although as many as 13,000 schools showed an interest in collecting and submitting data, these schools mainly covered urban areas, leaving "large gaps of knowledge" in rural areas, and leading the Domesday Project team to reach out to the Women's Institute, Scout Association, Guide Association and to farmers. Copyright issues In addition to preserving the project, untangling the copyright issues also presents a significant challenge. In addition to copyright surrounding the many contributions made by the estimated 1 million people who took part in the project, there are also copyright issues that relate to the technologies employed. It is likely that the Domesday Project will not be completely free of copyright restrictions until at least 2090 (assuming no further extensions of copyright terms). Interactive video The BBC Master-based system used to deliver the Domesday Project content, known as the Domesday Advanced Interactive Video (AIV) System, was also intended as a platform to support other interactive video applications, integrating with programming languages such as BASIC and Logo via the operating system. Opportunities were perceived for the introduction of the technology beyond the education sector and into various areas of the public and private sectors, estimating "300,000 potential business customers". Acorn set up a subsidiary, Acorn Video, offering the platform under the name Master Video with a choice of Philips or Pioneer laserdisc player for £3220, or £3750 for a more compact version. (This ostensibly followed on from earlier products: the Acorn Interactive System, based on the BBC Micro and Pioneer or Philips laserdisc player, which only supported unidirectional control of a laserdisc player via a serial link, and the Viewpoint Interactive Video Workstation.) BBC Enterprises and Virgin released interactive video discs for education. Following on from the initial Domesday content, the Ecodisc from BBC Enterprises provided an ecological simulation of Slapton Ley nature reserve designed to complement biology and ecology field trips at secondary school level. It was priced at £169 plus VAT, with one side of the disc containing the interactive content and data, the other side containing the BBC Schools Television programme Ecology and Conservation. Virgin's North Polar Expedition title, in contrast to Ecodisc, provided the software to support interaction on separate floppy disks instead of as LV-ROM content. It was priced at £199 plus VAT, and was reportedly a "testbed for CDI applications" planned by Virgin Publishing. Having received one unfavourable verdict that the