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Introduction to Digital Preservation: Emulation

Subjects: Digital Library

What is emulation?

An "emulator" is a software which mimics the behaviour of another computer environment. It is used in digital preservation to access software and digital files which require obsolete technological environments to run. For example, an organization could use a Windows 3.1 emulator to access a WordPerfect file from 1994 on the document editing software which originally created it (Corel WordPerfect version 7.x).  

Emulation software has been developed by gaming enthusiasts since the early 1990s, but has also sparked debate and interest within the digital preservation community since the early 2000s. While emulation environments were originally seen as complex and time consuming to set up, new developments such as in-browser-emulation has lowered the barrier to use. Today, one of the biggest obstacles to using emulation software is instead around legal concerns. The licensing landscape for obsolete software and Operating Systems required for emulation is still complex.

 

Benefits

There are a number of benefits to using emulation for accessing file formats and obsolete software. These include:

  • The ability to access complex digital objects such as games, virtual reality and apps
  • Allowing users to interact with digital objects in their original environments, enabling them to experience what it would have been like to create and use older software. In other words, it can provide researchers with valuable context about the environment a creator was working in at the time.
  • When used at scale, it can provide access to large parts of a collection

 

 

Emulation as a service

Emulation as a Service (EaaS) is a scalable service model to allow organizations to access emulated environments and deliver them to users. The EaaS architecture simplifies access to preserved digital objects and provides original environments to users. It utilizes ready-made emulation components and a flexible web service API for tailored digital preservation workflows.

There are some demo use cases for EaaS available here.

One project which used Eaas in the cloud was Rhizome's Theresa Duncan's art game CD-ROMs from the 1990s. By providing access to them on the web, users can play the games without needing to download and install any additional software or disk images to their computer. The games Chop Suey, Smarty, and Zero Zero are available to play using an emulator here.

 

Drawbacks

There are a number of drawbacks to emulation, which do not always make it a practicable choice:

  • Acquiring rights to legacy software can be difficult 
  • New emulators are required as more technology becomes obsolete
  • Emulators are themselves software which are at risk of becoming obsolete, and requires ongoing maintenance and investment 
  • Support for many emulators is reliant on the goodwill and enthusiasm of the open source community 
  • Emulation is not always appropriate to users' needs. For example, a researcher looking to aggregate information from multiple databases may not wish to access it in a closed off emulated environment 

Further information

Game emulation remains a very popular example of using emulators to provide access to original files. It does strip the game of the original hardware, but it creates a software environment where the original game can be played on a variety of devices, from small computers (like the raspberry pi), to mobiles, special devices (the mini NES and SNES systems) and the web. The Internet Archive provides access to a number of emulated games, such as those for MS DOS, and emulated computer environments like the Mac OS 7.0.1 from 1991.