Data Services Newsletter

Volume 21 : No 1 : Spring 2019

Federated MetaData Aggregator (MDA)

Introduction

The IRIS MetaData Aggregator has been redesigned to show metadata summaries from global data centers supporting FDSN Web Services. In addition to SEED metadata information, MDA presents other details such as data availability, virtual network affiliations, response curves, and links to dynamic maps. MDA adds to the IRIS DMC’s suite of federated web tools including GMAP and Wilber 3, which collectively provides users a convenient view of the station holdings provided by all participating FDSN data centers.

MDA exposes five levels of metadata summary: network list, network, station, location and channel. At each summary level, metadata from different federated datacenters is related using SEED metadata identifiers and time spans.

Input parameters are specified in the URI as extensions of the form: http://ds.iris.edu/mda/[network]/[station]/[location]/[channel].

The summary level is implied by the input parameters; i.e. if only a network is specified, the network summary level is returned. Users can navigate MDA by entering the input parameters in the URL directly or by following links on each summary page.

Screenshot for all networks list

The Power of Federation

Instead of directly querying the IRIS DMC database, MDA now sources SEED metadata information from the IRIS FedCatalog Web Service. The FedCatalog periodically collects metadata from (currently 20) participating FDSN datacenters. The FedCatalog then exposes the collected metadata through a single web service interface.

Federation allows MDA to present SEED metadata summaries from datacenters other than the IRIS DMC. Since it is possible for metadata information to vary between FDSN datacenter holdings, MDA exposes places where metadata differs by displaying metadata discrepancies next to each other.

Screen shot of a network summary containing metadata discrepancies

Filtering Metadata Summaries

A new “Filter” inline form has been added to summary pages for limiting page results. For example, if a summary page shows metadata from several different datacenters then a filter could be applied to limit the results to one datacenter. Additionally, a new “Context” feature provides anchors to network, station, or channel epochs on the page. This enables quickly jumping to a timespan on a page without scrolling through the page.

Screen shot displaying MDA filters and context menu

Timeseries Data Availability

MDA displays availability info for datacenters that support a data availability service compatible with the DMC’s irisws-availability service (under review to become an FDSN standard). Seismic data availability information is harvested multiple times daily from these availability services and is displayed by hovering over the green “A” icon (see figure below). MDA will expand to show availability summaries from more datacenters as they add a supported availability service. Clicking an availability hyperlink in the popover returns more detailed information from the availability web service.

Screen shot displaying availability information for an element by hovering over the “A” availability icon

Conclusion

The Metadata Aggregator (MDA) tool allows users to interactively explore metadata summaries from IRIS DMC and other federated data repositories. It is an example of how IRIS continues to integrate FDSN-wide data discovery into tools. In exposing metadata to a network of data repositories outside of the IRIS DMC, the scope of seismic data discoverable for all researchers expands greatly.

by Nick Falco , Adam Clark , Mick Van Fossen and Bruce Weertman (IRIS DMC)

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