Data Services Newsletter

Volume 3 : No 3 : September 2001

What happened to FISSURES? Or exactly what is the Data Handling Interface?

FISSURES is an effort to define object-oriented seismic classes so that software developers can use standard objects for seismology. Additionally FISSURES uses a distributed computing technology called CORBA (Common Object Request Broker Architecture) to allow software systems to work across the Internet in a platform independent and computer-language neutral manner.

The IRIS DMS (relying heavily on efforts by Philip Crotwell at South Carolina) spearheaded the original definition of the seismic classes and the overall FISSURES framework. We then focused our efforts on developing tools to effectively deliver seismic data (waveforms and hypocenters) from the DMC to the end users. This article will provide a brief summary of our current activities.

Object Oriented Approaches

Objects are self-contained software modules that consist of attributes and methods. The attributes are the data and parameters contained within a specific object. Methods are things the object can do to itself. For instance if one had a “ seismogram object” the attributes might be its sample rate, starting time and the individual time series values. The methods might be things such as re-sampling or plotting. One can think of objects as containers that hold attributes and methods.

Figure 1: The seismic object

The Interface Definition Language (IDL) is the standard interface software that allows an object to communicate with other objects. I think of IDL as flanges that attach the objects to the network.

Figure 2: The IDL

Finally, one can think of CORBA as the infrastructure or plumbing that connects the various objects together through the IDL flanges. IDL and CORBA are what allow the distributed objects to work together to form an application.

Figure 3: CORBA plumbing

The Data Handling Interface or DHI

The IRIS DMC currently has three FISSURES compliant services in operation. These services are:

  • An event service
    • This service takes information from the DMC Oracle DBMS and serves selected events to a FISSURES enabled client.
  • A network service
    • This service provides information about seismic stations, their recording channels and the responses for those channels to a FISSURES client. The information comes from the Oracle Database.
  • A waveform service
    • This service provides FISSURES seismogram objects to a client somewhere on the Internet. Currently the waveforms can come from the new IRIS FARM or SPYDER® Products and work is currently underway for data to come from the new IRIS real time system, BUD (see this previous newsletter article).

Figure 4: DHI services

DHI Clients

Work is about to begin on a series of clients that can exploit information from the DMC services. One such client will be developed by the Moscow Data Center. This client will provide WEED functionality but using the FISSURES technology. One distinct advantage to this approach is that the information about events and stations will always be current; information about events and stations and channels that WEED requires will come directly from the Oracle DBMS at the IRIS DMC. The WEED client will determine the data windows needed, identify them to the Waveform service at the DMC and receive the waveforms back on their client machine.

Figure 5: DHI clients

Other clients that are being (or may be) developed include:

  • The Virtual Seismic Network (VSN) Explorer by the IRIS E&O program by the University of South Carolina
  • A real time waveform display from the BUD by Chris Laughbon of the IRIS DMC
  • An equivalent of the Standing Order for Data (SOD) system by the University of South Carolina
  • A C (and perhaps Fortran) callable implementation of the Evalresp application by ISTI
  • A link into MatLab from the DHI by the University of Washington

We will be announcing the availability of these clients in this IRIS DMS Newsletter as they become available and we will be looking for interested parties to beta test them. If you are interested, please contact us

by Tim Ahern (IRIS Data Management Center)

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