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Records

The databases for which the WFDB library was designed consist of a small number of records, each of which is quite large (typically a megabyte or more). Before 1990, database records usually originated as multi-channel analog tape recordings that had been digitized and stored as disk files. For this historical reason, they are sometimes referred to as tapes, although most newly created records are digitally recorded onto disk media. Each record contains a continuous recording from a single subject. A typical application program accesses only a single record, and most (if not all) of the access within the record is sequential. Much less frequently, it may be of interest to compare the contents of several records, or to select sets of records. These databases are therefore qualitatively different from those for which conventional database management software is written.

Records are identified by record names of up to 20 characters (the limit is MAXRNL, defined in ‘<wfdb/wfdb.h>’). For example, record names in the MIT DB are three-digit numbers, those in the AHA DB are four-digit numbers, and those in the ESC DB are four-digit numbers prefixed by the letter ‘e’. You may create database records with names containing letters, digits, and underscores. Case is significant in record names that contain letters, even in environments such as MS-Windows for which case translation is normally performed by the operating system on file names; thus ‘e0104’ is the name of a record found in the ESC DB, whereas ‘E0104’ is not. A record is comprised of several files, which contain signals, annotations, and specifications of signal attributes; each file belonging to a given record normally includes the record name as the first part of its name. A record is an extensible collection of files, which need not all be located in the same directory, or even on the same physical device. Thus it is possible, for example, to create a local disk file of your own annotations for a record read from a web server or a CDROM, and to treat your file as part of the record.


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George B. Moody (george@mit.edu)