About Hermes

Hermes is, concisely stated, a platform technology for high-throughput data visualization and analysis. It is capable of gathering data from multiple sources; providing remote access to that data (both in real time and retrospectively) via the Internet; and processing the incoming data in user-customizable ways.

"Platform technology" is an oft-used buzzword that may often translate loosely into "a technology that purports to do everything but does nothing". A platform technology can only be considered useful when it has found a specific application - that is to say, when it has been implemented. Hermes was designed with the high-level goal of accommodating any type of data, but it has been successfully implemented and strenuously tested in physiological data applications at MIT.

Hermes is intended to provide an easy and intuitive mechanism to serve users as a web-based portal for viewing incoming data and/or analysis results retrospectively and in real-time.

Record Selection

When the HERMES Java applet starts up, a tabbed pane opens in a new window, with the 'Record Selection' tab active. Select a database, and then a record within that database (and, if desired and available, a set of annotations).

Databases, Records, and Annotators are all chosen in a similar fashion. After selecting the Database of interest from the Database drop-down menu, the Records and Annotators of the database are made visible via similar drop-down menus.

Verify your choices by looking at the 'Selected:' values shown above each drop-down menu, and click on 'Load Record' if satisfied. To view data from a different Database, click on 'Select New Database' to refresh the Record and Annotator menus.

Waveform Viewer

After clicking on 'Load Record', the 'Waveform Viewer' becomes active. Waveforms from the chosen record are drawn over a grid with intervals of 0.2 seconds and 0.5 mV. If a set of annotations was chosen, these appear along the bottom edge of the plot.

There are currently three methods to move through the record. The controls are below the waveforms; move your mouse pointer over them to view their functions, which are shown as "tooltips".

• To view the record as a movie, simply click (Play Waveform as movie). Click (Pause waveform) to interrupt playback, and 'Play' again to resume the movie. The 'Adjust Speed' slider to control the playback rate (network delays may limit your speed, however).
• You can also navigate using the 'Next' and 'Previous' buttons. Four such buttons allow you to move by half or all of the width of the window, forward or back, and two more allow you to search through the record for the next or previous occurrence of an annotation (which you may choose from the drop-down list between the search buttons).
• There is also a time line representing the entire record, just below the waveform plot. Drag the time line's pointer to any desired location in the record.

Use 'Reset' to move to the beginning of the record and re-initialize the zoom and speed slider controls to their default postitions.

Signal Visibility

It can be difficult to understand a view of many signals. When viewing a record with multiple signals, you may right-click over the waveform plot to obtain a popup menu of the available signals appears. Click on any of these signals to hide them or to make them reappear. (This feature is unavailable in "movie" mode.)

Saving Waveform Plots

Even if your system offers a way to record screenshots (not available on all platforms), a better way to save your output is to get a high-resolution PostScript plot by email. Erase the words "ENTER YOUR ADDRESS" and type your email address in the box, then click on 'Email To:'. Your plot is made with better than screen resolution on the PhysioNet server and sent to you immediately by email.