Finally, the tools should not impose any particular format on the event data files, but, instead, be able to adapt to any format. Event data refers to the very rich data sets produced by photon counting detectors such as those commonly used in high-energy telescopes. These tags are retained through the later processing of the events, so that a scientist analyzing the data can use filtering techniques to examine subsections of the complete data set, or form secondary data products such as images or light curves by binning the data in any desired manner. Another typical feature of event data sets is the presence of auxiliary information from the telescope or the spacecraft on which it may be operating, in addition to the events themselves. Event data sets will typically consist of several event lists and tables of auxiliary information, along with various filters that may have been established, and images and light curves that have been computed.
Scientific meaning is attached to event data objects.
We build upon existing libraries, which support basic objects, and provide applications that manipulate event data. We have developed a model for event data that describes the objects and operations needed for their analysis. The dataset is an object that contains all of the component parts of an event data observation in a directory-like structure. It supports operations to add, remove, and list contained objects. Every object in the dataset has an associated property list, which is a set of zero or more properties.