Metacat

DataONE Member Node Support

===========================

DataONE_ is a federation of data repositories that aims to improve

interoperability among data repository software systems and advance the

preservation of scientific data for future use.

Metacat deployments can be configured to participate in DataONE_. This

chapter describes the DataONE_ data federation,  its architecture, and the

way in which Metacat can be used to participate as a node in the DataONE system.

What is DataONE?

----------------

The DataONE_ project is a collaboration among scientists, technologists, librarians,

and social scientists to build a robust, interoperable, and sustainable system for

preserving and accessing Earth observational data at national and global scales.

Supported by the U.S. National Science Foundation, DataONE partners focus on

even when those repositories use divergent underlying software and support different

data and metadata content standards. DataONE defines a common web-service service

programming interface that allows the main software components of the DataONE system

to seamlessly communicate. The components of the DataONE system include:

* DataONE Service Interface

* Member Nodes

* Coordinating Nodes

* Investigator Toolkit

Metacat implements the services needed to operate as a DataONE Member Node,

as described below.  The service interface then allows many different scientific

software tools for data management, analysis, visualization and other parts of

the scientific lifecycle to directly communicate with Metacat without being

further specialized beyond the support needed for DataONE.  This streamlines the

The DataONE Service Interface

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

REST_ web services that can be implemented by various data management software

systems to allow those systems to effectively communicate with one another,

exchange data, metadata, and other scientific objects.  This `DataONE Service Interface`_

expectations for software components that wish to participate in the DataONE

federation. This service interface is divided into `four distinct tiers`_, with the

intention that any given software system may implement only those tiers that are

relevant to their repository; for example, a data aggregator might only implement

the Tier 1 interfaces that provide anonymous access to public data sets, while

a complete data management system like Metacat can implement all four tiers:

1. **Tier 1:** Read-only, anonymous data access

2. **Tier 2:** Read-only, with authentication and access control

3. **Tier 3:** Full Write access

4. **Tier 4:** Replication target services

.. _four distinct tiers: http://releases.dataone.org/online/d1-architecture-1.0.0/apis/index.html

Member Nodes

~~~~~~~~~~~~

particular scientific communities, manage and preserve their data and metadata, and

provide tools to their community for contributing, managing, and accessing data.

DataONE provides a standard way for these individual repositories to interact, and helps

to coordinate among the Member Nodes in the federation.  This allows Member Nodes

to provide services to each other, such as replication of data for backup and failover.

To be a Member Node, a repository must implement the Member Node service interface,

and then register with DataONE.  Metacat provides this implementation automatically,

and provides an easy configuration option to register a Metacat instance as a

DataONE Member Node (see configuration section below). If you are deploying a Metacat

instance, it is relatively simple to become a Member Node, but keep in mind that

DataONE is aiming for longevity and preservation, and so is selecting for nodes

that have long-term data preservation as part of their mission.

Coordinating Nodes

~~~~~~~~~~~~~~~~~~

allow Member Nodes to easily interact with one another and to provide a unified

view of the whole DataONE Federation.  The main services provided by Coordinating

Nodes are:

* Resolution service to map unique identifiers to the Member Nodes that hold data

* Authentication against a shared set of accounts based on CILogon_ and InCommon_

* Replication management services to reliably replicate data according to

  policies set by the Member Nodes

* Fixity checking to ensure that preserved objects remain valid

* Member Node registration and management

* Aggregated logging for data access across the whole federation

Three geographically distributed Coordinating Nodes replicate these coordinating

services at UC Santa Barbara, the University of New Mexico, and the Oak Ridge Campus.

Coordinating Nodes are set up in a fully redundant manner, such that any of the coordinating

nodes can be offline and the others will continue to provide availability of the services

without interruption.  The DataONE services expose their services at::

  https://cn.dataone.org/cn

And the DataONE search portal is available at:

  https://cn.dataone.org/

.. _CILogon: http://www.cilogon.org

.. _InCommon: http://incommon.org

~~~~~~~~~~~~~~~~~~~~

DataONE, the third component represents a library of software tools that have been

adapted to work with DataONE via the service interface and can be used to

discover, manage, analyze, and visualize data in DataONE.  For example, DataONE

plans to release metadata editors (e.g., Morpho), data search tools (e.g., Mercury),

data access tools (e.g., ONEDrive), and data analysis tools (e.g., R) that all

know how to interact with DataONE Member Nodes and Coordinating Nodes.  Consequently,

scientists will be able to access data from any DataONE Member Node, such as a Metacat

node, directly from within the R environment.  In addition, software tools that

are written to work with one Member Node should also work with others, thereby

greatly increasing the efficiency of creating an entire toolkit of software that

is useful to investigators.

programming language can be adapted to interact with DataONE.

In addition, to ease the process of adapting tools to work with DataONE, libraries

are provided for common programming languages such as Java (d1-libclient-java)

and Python (d1_libclient-python) are provided that allow simple function calls

to be used to access any DataONE service.

------------------------------------

Configuring Metacat as a DataONE Member Node is accomplished with the standard

Metacat Administrative configuration utility. To access the utility, visit the

following URL::

  http://<yourhost.org>/<context>/admin

where ``<yourhost.org>`` represents the hostname of your webserver running metacat,

and ``<context>`` is the name of the web context in which Metacat was installed.

Once at the administrative utility, click on the DataONE configuration link, which

should show the following screen:

.. figure:: images/screenshots/screen-dataone-config.png

   :align: center

   The configuration screen for configuring Metacat as a DataONE node.

Being a replication target

~~~~~~~~~~~~~~~~~~~~~~~~~~

TODO: Describe the configuraiton for acting as a replication target.

Replication Policies

--------------------

TODO: Describe the replication policies for objects in DataONE.

Access Control Policies

-----------------------

TODO: Describe access control for objects in DataONE.