Earthnet Home 14-Feb-2012    
 Introduction
Home
Background
 Architecture
Abstraction Models
Software API
 Benefits
Benefits and Characteristics
 Download
General Specifications
Mission Specific Documentation
Schema Sets
Sample Products
Software and API
 More Resources
Related Links
Contacts
  
BENEFITS and CHARACTERISTICS


 
SAFE Main Characteristics
  

SAFE uses the latest available technologies to achieve its goals of preserving the archived data for a long-term, facilitating the conversion into different formats, simplifying the extraction from the archive and enhancing their utilization by end-users and/or processing systems.

During the development of SAFE, particular attention was put to the long‑term preservation aspect. To this end, the information model of the generic Archival Information Package (AIP), introduced in the ISO 14721:2003 OAIS (Open Archival Information System) Reference Model [1] [2], has been used.

Furthermore, SAFE is based on the XFDU (XML Formatted Data Units) standard under development by the CCSDS (Consultative Committee for Space Data Systems). In its essence, SAFE is a profile of XFDU, and it restricts the XFDU specifications for the specific utilization in the EO domain.

 
Relationship with XFDU
  

The main rationale for the emergence of the “XML Formatting Data Units” – XFDU is (credit CCSDS):

The current CCSDS Standards for Data Packaging have not undergone a major revision in 15 years. The computing environment and the understanding of metadata have changed radically:

  • Physical media à Electronic Transfer
    • The primary form of access to, and delivery of, both archived and recently produced data products has shifted from hard media to include substantial network delivery
  • No standard language for metadata à XML
    • After 'bits' and 'ASCII', the language 'XML' can be viewed as the next universal data standard, as it has grown exponentially
  • Homogeneous Remote Procedure Call à CORBA, SOAP
    • Communicating heterogeneous systems are increasingly using standard remote procedure calls or messaging protocols. The primary RPC and messaging protocol for the WWW is SOAP, an XML based protocol
  • Little understanding of long-term preservation à OAIS RM
    • The OAIS Reference Model has become a widely adopted starting point for standardization addressing the preservation of digital information. The OAIS defines and situates within functional and conceptual frameworks the concepts of Information Packages for archiving (Archival Information Packages, or AIPs), producer submission to an archive (Submission Information Packages, or SIPs), and archives dissemination to consumers (Dissemination Information Packages, or DIPs).
  • Record formats à Self describing data formats
    • Commensurate with XML, and rapidly growing computing power and storage capabilities has been an increasing tendency to use data formats that are more self-describing.

 Further, there are a number of new requirements that are needed in the Space domain to facilitate such functions as being able to describe multiple encodings of a data object, and to better describe the relationships among a set of data objects. Therefore it is necessary to define a new set of packaging standards while maintaining the existing functionality.

SAFE has been designed to fully comply with the current definition of this emerging standard, offering several advantages and opportunities, among which:

  • inheriting from experiences gathered from the several international agencies, laboratories and companies composing the CCSDS
  • sharing at least the same compliance level with the OAIS reference model
  • making SAFE immediately compatible with the software due to be developed within or outside ESA scope
  • facilitating interchanges between several archiving management systems maintained by agencies following the CCSDS recommendations
  • supporting the development of XFDU by providing the CCSDS working groups with returns from experience of using and implementing the intermediate working drafts
  • supporting the development of XFDU by providing software material implementing the standard.
  • SAFE Benefits

The adoption of a common format like SAFE gives major benefits for a cost-effective long‑term preservation and exploitation of these data for several reasons:

  • SAFE is mainly devoted to the long-term preservation of data, as its full compliance with the CCSDS/ISO OAIS RM and XFDU standards reveal.
  • SAFE permits an easier and more effective migration of data to other future standards.
  • SAFE permits and easier reformatting to other formats, including end-user formats for products distribution.
  • SAFE will easy the maintenance of the SW that use the data, even historical, thus decreasing the chances of obsolescence and improving their usability.
  • SAFE being self describing, it greatly facilitates the format maintenance.
  • SAFE format documents are built automatically from the XML-Schemas, so the maintenance of the SAFE format is more robust with respect to “old-fashion” formats.

SW that access SAFE-formatted datasets will benefit from the usage of the same SAFE XML Schemas for reading and writing the datasets. This greatly improves the overall cycle of creation/ingestion/quality control/transformation/distribution of the datasets.

top

 

  Higher level     pr   Print version             Last modified: 11-Jul-2011