LTDP SAFE Wiki
Welcome to the SAFE Wiki!
The SAFE (Standard Archive Format for Europe) has been designed to act as a common format for archiving and conveying data within ESA Earth Observation archiving facilities intending to provide solutions for data packaging and EO Long-Term Data Preservation (LTDP).
This wiki, complements the information contained in the Official SAFE project web page which provides details on the SAFE format and is the official site maintained by ESA for the distribution and maintenance of the standard formats, including the documentation, related schemas and software tools.
The wiki is intended to provide updated information on the SAFE standard evolution and resources (e.g. discussion forums, support services, etc...) for the SAFE community.
The ESA's Earth Observation missions archive has to be maintained for at least ten years after the end of the mission. The management of this vast amount of heterogeneous datasets poses problems for their long term preservation, generating the need to establish a clear strategy for the management of these archives.
One of the reasons that contribute to the high operations and maintenance costs of the long term archive is the excessive proliferation of diverse and heterogeneous data formats, caused by mainly three reasons:
- The lack of an agreed standard in the EO community, reason for which the formats tended to be specific for the sensor(s) each missions carried on board.
- Legacies from old ground segments architectures, which tended not to reuse elements previously developed.
- The non-mature status, until recently, of the information technologies and standards used to describe and package the data, preventing the creation of a unique format able to satisfy at the same time the requirements for the long-term preservation of the data and their handling in the processing centres.
Taking all this into account, in early 2004 ESA set up a project called HARM (Historical Archives Rationalization and Management), which aimed mainly at converting its historical datasets into a new format able to ensure the long-term preservation of its holdings.
The format developed within the HARM project was named Standard Archive Format for Europe (SAFE).
SAFE primary goal is to preserve the archived data for a long-term period, facilitating the conversion into different formats, simplifying the extraction from the archive and enhancing their utilization by end-users and/or processing systems.
It has been developed conforming the OAIS (Open Archival Information System) reference model and related standards.
The SAFE format is based on the XFDU (XML Formatted Data Units) data packaging format standard and in its essence, can be considered as a profile of XFDU, restricted to the utilization in the EO domain.
Actually, experience has demonstrated that packaging and archiving several processing levels or auxiliary data in a common format may be effective in many situations. SAFE undergo this concept by offering a single framework for packaging a large variety of information.
The current standards for data packaging have not undergone a major revision in more than 15 years and the computing environment and the understanding of metadata have changed radically.
New requirements have been identified in the Space domain for data encoding and data object description and a new set of packaging standards have to be defined but keeping the existing functionality.
Additionally, the usage of compressed data formats (e.g. Sentinel satellites) and the wish to archive different product levels, have introduced new requirements for data archival. Moreover, other successful standardisation activities not available when the SAFE format was created, suggest an improvement of the metadata model used in SAFE.
As result, the SAFE format has been reviewed to identify new extensions or alignments derived from user necessities. This revision has been carried out in collaboration with European stakeholders in the area of Earth Observation data archiving endorsed via public review process.
As outcomes of the review the following changes with respect to the previous version were agreed:
- Adoption of the OGC Earth Observation Metadata profile of Observations & Measurements (EOP O&M) as mandatory metadata model for EO products.
- Each SAFE EO product shall contain enough information to access related auxiliary/ancillary files inside a long-term archive.
- Adoption of a standard language to provide the representation information for binary data. The OGF Data Format Description Language (DFDL) has been designated as the standard language for this purpose.
- The representation information has to be stored in a different package than the data that it represents.
Currently, a draft version of the new SAFE specification is under internal review to verify how the documentation is aligned with the new requirements.
SAFE 1.3 Standard core documentation (superseded)
The following documents apply to SAFE 1.3 but they are being upgraded completely.
|SAFE Primer (tutorial)||PGSI-GSEG-EOPG-FS-010-0001||1.1||23/06/2010|
|(Control Book 1) SAFE Core Specifications||PGSI-GSEG-EOPG-FS-05-0001||1.14||16/11/2010|
|(Control Book 2) SAFE Recommendation for Specialisations||PGSI-GSEG-EOPG-FS-05-0002||1.11||22/06/2010|
NOTE: These documents must be used just for background about SAFE format. The SAFE design is going to be deeply changed in SAFE 2.0.
SAFE Standard requirements for SAFE 2.0
The following requirements have been defined for the new version of SAFE format:
|LTDP SAFE Software System Specification||SAFE-GMV-SSS-001||2.0||31/05/2012|
SAFE 2.0 Standard core documentation
TBD - An updated version of the SAFE core documentation will be available after the PDR.
Public Reviews Schedule
The public reviews schedule where the SAFE standard shall be updated is the following:
- Software Requirements Review (SRR): Where the requirements for the final standard, toolset and infrastructure shall be reviewed:
|02/03/2012||Deadline for RIDs submission||-||-|
|27/03/2012||SRR collocation meeting||ESRIN||-|
|06/04/2012||Issue of SRR Review Report||-||-|
- Preliminary Design Review of the Core specifications (PDR-C): Where the SAFE core set of documents (i.e. the “SAFE Core”) shall be updated according the new requirements stated after the SRR:
|11/06/2012||Review Data Pack published in RID tool||-|
|25/06/2012||Deadline for RIDs submission||-|
|12/07/2012||PDR-C collocation meeting||ESRIN|
|30/07/2012||Issue of PDR-C Review Report||-|
Internal Reviews Schedule
- Preliminary Design Review (PDR): Where the SAFE specialisations and the final format design will be reviewed by ESA:
|19/09/2013||Review Data Pack published in RID tool||-|
|02/10/2013||Deadline for RIDs submission||-|
|24/10/2013 (updated)||PDR collocation meeting||ESRIN|
|11/11/2013 (updated )||Issue of PDR Review Report||-|
(*) This schedule is subject to change. Changes, if necessary, will be announced in this page.