Modular VO oriented Java EE service deployer

Abstract

The International Virtual Observatory Alliance (IVOA) has produced many standards and recommendations whose aim is to generate an architecture that starts from astrophysical resources, in a general sense, and ends up in deployed consumable services (that are themselves astrophysical resources). Focusing on the Data Access Layer (DAL) system architecture, that these standards define, in the last years a web based application has been developed and maintained at INAF-OATs IA2 (Italian National institute for Astrophysics – Astronomical Observatory of Trieste, Italian center of Astronomical Archives) to try to deploy and manage multiple VO (Virtual Observatory) services in a uniform way: VO-Dance. However a set of criticalities have arisen since when the VO-Dance idea has been produced, plus some major changes underwent and are undergoing at the IVOA DAL layer (and related standards): this urged IA2 to identify a new solution for its own service layer. Keeping on the basic ideas from VO-Dance (simple service configuration, service instantiation at call time and modularity) while switching to different software technologies (e.g. dismissing Java Reflection in favour of Enterprise Java Bean, EJB, based solution), the new solution has been sketched out and tested for feasibility. Here we present the results originating from this test study. The main constraints for this new project come from various fields. A better homogenized solution rising from IVOA DAL standards: for example the new DALI (Data Access Layer Interface) specification that acts as a common interface system for previous and oncoming access protocols. The need for a modular system where each component is based upon a single VO specification allowing services to rely on common capabilities instead of homogenizing them inside service components directly. The search for a scalable system that takes advantage from distributed systems. The constraints find answer in the adopted solutions hereafter sketched. The development of the new system using Java Enterprise technologies can better benefit from existing libraries to build up the single tokens implementing the IVOA standards. Each component can be built from single standards and each deployed service (i.e. service components instantiations) can consume the other components' exposed methods and services without the need of homogenizing them in dedicated libraries. Scalability can be achieved in an easier way by deploying components or sets of services on a distributed environment and using JNDI (Java Naming and Directory Interface) and RMI (Remote Method Invocation) technologies. Single service configuration will not be significantly different from the VO-Dance solution given that Java class instantiation that benefited from Java Reflection will only be moved to Java EJB pooling (and not, e.g. embedded in bundles for subsequent deployment).