METAMOD overview

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Introduction

This document assumes that the basic METAMOD software are working on the various servers where METAMOD are intended to run. How to achieve this is described in a separate document: ... The current document describes how to use the software to create a cluster of one or more co-operating METAMOD applications (or METAMOD instances).

Data base

All the METAMOD instances in a cluster share a common data base. This data base is divided into the following parts:

Metadatabase

SQL Database for Metadata. This can be shared among different METAMOD instances

User database

SQL Database for User administration. Each METAMOD instance must have it's own private user database

XML archive

Metadata file archive based on XML

Data repository

Archive of netCDF files

One of the METAMOD applications in a cluster is responsible for the SQL metadata database. Initialization and administration of the metadata database are done through this application, which is called the base application. Each METAMOD instance must administer its own user database.

Although the METAMOD instances in a cluster may operate on different servers, they must share a common file system where the XML archive and the Data repository resides. Technically they may reside on different file systems, but for each file, the file paths on the various servers must be the same. Furthermore, for a smooth operation, the clocks on all the involved servers must be synchronized.

The SQL databases may reside on a separate server, different from any of the servers where the METAMOD instances run.

METAMOD functional modules

The METAMOD software comprise a broad range of functionality. The software is divided into different modules, each representing a separate set of related functionality. One such module is the BASE module, which is used in the base application described above. A METAMOD instance may use any combination of modules, except for the WEB module which is mandatory.

The only restriction is that one and only one application in a cluster must use the BASE module to initialize the metadata database. Each application must initialize its own user database however.

The METAMOD software comprise the following modules, which may be disabled unless otherwise noted:

WEB

Web interface for search, file upload, editing metadata, system administration and web services (RSS, OAI-PMH). This module is required, although some of the services may be disabled.

BASE

Used for creating the SQL databases. Since every METAMOD instance must have its own user database, this is also required.

UPLOAD

Services for uploading (or registering) netCDF files (via web, ftp).

HARVEST

Service for harvesting metadata from internet servers offering OAI-PMH support.

PMH

OAI-PMH provider service. See http://www.openarchives.org/.

THREDDS

Used for automatic building of THREDDS catalogs that may be utilized by a THREDDS Data Server to access the data repository.

Directory structure

On each server where METAMOD should run, the generic METAMOD software must be available in some directory. If you installed METAMOD using a met.no Debian package it will be located in /opt/metamod-2.x (where x denotes the minor version). In the description below, this directory is called the installation directory.

In addition to the generic installation directory you need a configuration directory. This directory contains configuration files, style sheets etc., and also files regulating metadata requirements. An example application configuration directory is included in the generic installation directory (the app/example subdirectory of the installation directory).

The main subdirectories of the generic installation directory are:

base

Files only used in the BASE module

upload

Files only used in the UPLOAD module (scripts only, the user interface is implemented in Catalyst)

harvest

Files only used in the HARVEST module

thredds

Files only used in the THREDDS module

common

Files used by several modules

catalyst

Perl Catalyst framework files used for the WEB module

app

Contains the example application source directory, as well as default configuration settings

docs

METAMOD documentation directory