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Universal Storage Scheme (mContext)
The Universal Storage Schemes Project (also known as mContext) will allow XML information to be stored in a space-efficient representation which also maintains low access and update costs for all of the desired operations.

The popularity of XML as a data representation language has produced a wealth of research on efficiently storing and querying tree structured data. As the amount of XML data available increases, it is becoming vital to be able to not only query and maintain this information quickly, but also store it in a compact manner.

The aim of this project is to allow XML information to be stored in a space-efficient representation which also maintains low access and update costs for all of the desired operations. This is especially critical for devices with limited resources such as handheld computers, sensor networks or mobile phones.  

What will this research achieve?

The goal of this research is to deliver a compact storage scheme for XML, i.e., a space-efficient representation of the data structure which also maintains low access and update costs for all of the desired primitive operations for data processing. The flexibility of XML makes finding a scheme which satisfies all these requirements at the same time extremely challenging. When looking for a compact storage scheme for XML, there are several issues that need to be addressed. For example, it has to support fast operations, especially we are considering software applications that target people on the move. Moreover, if intensive compression methods are employed, they need to be optional and can be switched on or off due to low computation power of some mobile devices. 

What are the key features?

Apart from being space-efficient, the solution will have the following features:

  • Support fast navigational operations: Many XML applications, such as collaborative document editing systems, depend upon efficient tree traversal, using a standard interface such as DOM (Document Object Model). Previous research demonstrated that a combination of navigational and structural join operators is most effective for evaluating queries. Hence, it is imperative that the storage scheme supports fast traversal of the XML tree, in all possible directions, preferably in constant time or near constant time.
  • Support efficient insertions and deletions: Most space-efficient XML storages do not allow efficient update operations such as node insertion. This can be a critical concern in many database applications. Therefore, the solution should provide a scheme which allows fast update operations.
  • Support efficient join operations: Current query optimization techniques for XML make heavy use of the structural join, which relies on a constant time operator to determine the ancestor-descendant relationship between two nodes. Thus, any general XML storage scheme should also support such an operator very efficiently.
  • Separate the topology, schema and text of the document: All XML query languages select and filter results based on some combination of the topology, schema and text data of the document. To allow efficient scans over these parts of the document, it is natural to find a representation that partitions them into separate physical locations.
  • Permit extra indexes: Many applications may require addition specialized indexes to be built upon their data. Therefore, a general purpose database system is required to provide a storage representation, such that it is flexible enough to accommodate such need. More specifically, the storage scheme used by the database system must provide a simple, efficient and stable way of referencing its stored data.

Commercial Opportunities

The mContext team is a soon to be a commercial spin-off from NICTA. Based on the above XML succinct representation scheme and augmented with an efficient text compression mechanism, its technology enables fast access to dynamic, high-value content on mobile phones and ultra-mobile personal devices. In essence, it enables these devices to "store more data than they can physically hold".

The team

Key publications

Awards

The mContext team has achieved several awards including 2007 CeBIT Australia's Early Innovator Award and best paper awards/prize from international research conferences.

Application

mContext allows the compression of large amounts of data on mobile devices. For example, mContext enables the entire Wikipedia (full text articles) to be stored, searched and accessed from your mobile phone. The iPhone / iPod Touch version is now available via Apple's iTunes. Other applications for Windows Mobile and J2ME devices are under beta test and will be available to public soon. See TiniWiki.com for more details.

Participants

The mContext team is looking for engagement with content publishers, marketers, application developers and mobile handset manufacturers.

NICTA has been working with Green Pea Software for applying the solution to mobile search. The prototype is named and trademarked as mContext.

We are also seeking to recruit highly motivated and qualified doctoral students to work with us. Please contact Raymond Wong for further information.