ESA New Generation Science
Archives (II) : Data Layer
ABSI: Archives Building Systems Infrastructure:• Common Scientific Archives Architecture.
• Set of tools and libraries.
• State of the art technology.
• Three tier architecture.
• Quick building and deployment.
• Easy maintenance.

Query Manager Module Æ Metadata Access
Query Handler• Point of entry for all requests of the Query Manager• Requests processing steps:• Call Query Builder to build a Query Object (if needed)• Call the corresponding DAO• Process the result with the Result Handler (if needed)• Give back the results• Handles all requests related with metadata information using state of the art
software, such as:• Connection Pooling• Statement Pooling• Distributed Query & Objects Cache• Composed of five different modules:• Query Handler• Query Builder• Geometry Handler• Result Handler• Data Access Objects (DAOs)

Geometry Handler• Receives an geometrical condition• This condition is replaced with spherical datatypes, functions and operators provided by thePostgresql module PgSphere

DAO (Data Access Object) Layer• The DAO layer encapsulates access to stored metadata• Hibernate mapping relational tool is used for several reasons:• Maps database tables to java classes• Provides data query and retrieval facilities• Manages connection pooling• Manages query and object cache• Offers portability between different databases

Result Handler
Data Layer Requirements• Access to metadata and data products• Flexible granularity of data with millions of searchable elements• Short response times• Deliver an efficient and reliable access using open source technology:• Postgresql (database)• Spring (application framework)• Hibernate (persistence framework)• Our software is built on top of these software solutions to provide additional
functionality, through the following modules:• Query Manager Module Æ Metadata• Data Distribution Module Æ Data Products

Data Distribution Module Æ Data Access• Receives an object or a set of objects from theDAO layer, and “casts” them to the corresponding
project dependent object• Objects are recognized as simple (String,Integer,…) or complex elements of the project.

Query Builder• Receives a QueryBean object and returns an equivalent object which can be understood by the DAOLayers• If there are any geometrical conditions, the Geometry Handler is called and its result added tothe final result.
• The correspondence between the QueryBean entities and the database tables is achieved by the use ofxml mapping.
• After the target entities are known, the Dijkstra algorithm is used to “join” and extract the requested
attributes. The Dijkstra algorithm, conceived by Edsger Dijkstra in 1959, was chosen because:• It is a graph search algorithm that solves the shortest path problem for a graph, outputting ashortest path tree, which is often used in routing solutions.
• Can be reapplied to our database tables and their relationships.

• Handles all requests related with repository files.
• Data can be requested in different granularity levels, dependant upon the project.
• Once the module finds the data requested, a HTTP URL will be provided to the user for easy
data access. This URL is internally redirected to an FTP server.
• Offers synchronous and asynchronous data retrieval• Synchronous (Direct Download)• Data available in FTP holding area, accessible from HTTP (redirected)• Authentication required• Asynchronous (Shopping Basket)• Email notification when ready• Data available in FTP holding area, accessible from HTTP (redirected)• Authentication required• Retrieval of postcards, when available, is treated as a synchronous request.
• Animation sequences can be performed by date order retrieval of postcards

Use Case: Soho Science Archive• 3 levels of granularity in metadata display & data retrieval• 1 884 997 observations in the database• 765 356 coronal images in the database• 941 424 full disk size images in the database• 3 591 777 files in the data repository… and growing !
SOHO Science Archive
http://soho.esac.esa.int/data/archive/index_ssa.html
EXOSAT Science Archive (coming soon)
http://www.sciops.esa.int/index.php?project=SAT

04-08 Oct.
2009
ADASS XIX
SapporoEuropean Space Astronomy Centre (ESAC) - Villafranca del Castillo, Madrid (Spain)
I.Leon, C. Arviset, D.Baines, I. Barbarisi, J.Castellanos, N.Cheek, H.Costa,
N. Fajersztejn, M.Fernandez, J. Gonzalez, A. Laruelo, I.Ortiz, P. Osuna, J. Salgado,A. Stebe, D. Tapiador