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  1. What is a Virtual Observatory?
  2. What is ViRBO’s long-term plan?
  3. Why does ViRBO host files?
  4. What is the “small box” concept?
  5. What is SPASE?

1. What is a Virtual Observatory?

Recent articles related to Virtual Observatories include Weigel et. al, 2009 and Baker et. al, 2008. See also the Senior Review Proposal [1]. From [2]:

“A VO is a service that unites services and/or multiple data providers, with a "VxO" doing this for community "x."”

“… a suite of software applications on a set of computers that allows users to uniformly find, access, and use resources (data, software, document, and image products and services using these) from a collection of distributed product and service providers. A VO includes registries based on a metadata model, front-end applications, and connections to data providers.”

2. What is ViRBO’s long-term plan?

Most of the NASA Virtual Observatories were funded under 3-year proposals, and this period ended in 2009. The Virtual Observatories underwent a review in Fall 2009, and are expected to receive continued support. A more detailed plan for ViRBO is being prepared. More generally, from the review proposal [3]: "The primary function, then, of the VxOs in the next two to three years will be to complete resource descriptions and easy access to the data within their domains. Some of the latter task will be separated out into activities that clearly cross domains, and thus will be funded separately ..." Check the HPDE page for updates.

3. Why does ViRBO host files?

The "small box" Virtual Observatory concept (see next question for definition) says that a virtual observatory should only provide services on data in remote locations.

Our objective is to simplify the process of doing radiation belt research. Sometimes this requires doing things in a "non-VxO" way until a service becomes available that allows us to simultaneously do things the "VxO way" and meet user demands.

ViRBO locally holds two types of data.

  1. Data stored in temporary cache. This is data that would have been returned from a web service or a data provider, but the request would have taken too long to complete. For small data sets, it is more efficient and reliable to serve data from ViRBO's server, especially when we want to do transforms or filtering or to combine data from multiple locations. Ideally, there would be a service that provided our required speed and reliability and ViRBO would connect to this service. We are participating in the development of software that will enable such a service [4].
  2. The second is data in merged files. These are usually created for (a) users who want to do large-scale statistical studies on a very large data set that is difficult to create or (b) for validation and testing purposes on data analysis programs (e.g., QinDenton). That is, some of the merged files contain data that are used as inputs to data analysis programs. In order to reliably determine how changes to the analysis algorithms affect the output, the input must be the same.

Another reason that we locally hold data files is as a service to the community. Some of the data sets are from users at institutions that do not have easy access to a public ftp site. It was much easier for them to share their (generally small) data files using ViRBO than to set up a ftp site of their own.

In addition, we took on many of these data sets to fulfill obligations from our original proposal to develop ViRBO. Eventually these data sets should be migrated to a more appropriate place.

4. What is the “small box” concept?

Figure 1 The “small box” Virtual Observatory concept says that a virtual observatory should only provide services for data in remote locations.
Figure 1 The “small box” Virtual Observatory concept says that a virtual observatory should only provide services for data in remote locations.

The “small box” Virtual Observatory concept says that a virtual observatory should only provide services for data in remote locations, as shown in Figure 1 from [5].

In the first three years of operations, many virtual observatories have been involved in activities that fall outside of the “small box”. This happened for two reasons. First, some of the virtual observatories included such activities in their original 3-year proposal. Second, this happens when a tool or resource that a VxO needs to enable a service for their community does not exist, so they develop it on their own.

5. What is SPASE?

SPASE - (Space Physics Search and Extract) - a metadata model for Heliophysics data and related resource types which can describe each type of resource and their relationships.

SPASE is a metadata model (standardized descriptors) for heliophysics data and related resource types. For any given resource type, the data model specifies a set of "attributes" and their definitions and, for some attributes, specifies enumerated lists of valid values along with the definition of each.

SPASE descriptive standards are expected to facilitate registering, finding, understanding and accessing heliophysics data products, or parts thereof, now distributed across a broad heliophysics data environment. The "understanding" will come partly from SPASE-descriptors and partly from more detailed documentation files pointed to in SPASE descriptors.

SPASE is a description language for describing the holdings of scientific archives and the related entities necessary to find, understand, extract make use of their data holdings.

SPASE descriptions allow interested parties to identify if there are data of interest available, where it is available from, and how to make use of it once the data are acquired.

SPASE allows scientific archives to provide a consistent description for use by access and visualization tools to find and make use of their data holdings.

SPASE isn't about making data systems, but in describing systems that hold data (or possibly, process data, that seemed to be a bit of a debate at one point) for use by other systems.

Accessing individual values in data records will sometimes be enabled by SPASE descriptor content, but in other cases will need supplementary extra-SPASE information.

SPASE is NOT a data system NOR a language. It is at the least a set of standard descriptors and protocols for heliophysics-data metadata. It is designed for use by data systems (e.g., VxOs) to provide interoperable data search, access, retrieval and/or delivery functionalities.

The SPASE Group [6] develops and defines the SPASE metadata model and provides links to the basic tools that aid in the implementation and use of SPASE. The primary goal of SPASE group is to provide a metadata model for heliophysics that will allow VxOs, Resident Archives, and Active Archives to communicate at a high level about people, observatories, repositories, and instruments. Resources include people, observatories, instruments, repositories, and data. The metadata model will include sufficient semantics to enable scientifically relevant searches. The metadata model will include an abstract data model which will support the description of data content at a parameter level. The SPASE Group is to provide specifications to enable the free and open exchange of resources. This includes a query language compatible with the SPASE metadata model and services to support the registration, finding, and accessing and presentation of resources. The SPASE group will provide specifications for the expression of all persistent information in a common, accessible form (currently XML).

SPASE Metadata Working Group (SMWG) - The SPASE Metadata Working Group [7] is a group that manages a distributed and versioned repository of high-level SPASE metadata and encourages common conventions in its implementation.

The SPASE Query Language - [8] is being developed and will provide a semantic model for queries of SPASE repositories.

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