Pretty well all I knew about Geoshare before the course was that it worked with half links. I had also heard of the "n-squared" problem which is the rapid rise in the number of point-to-point data links needed as the number of data sharing applications increases. The Geoshare solution is to define a standard file format to which all applications can read or write data through what is termed a "half link". The standard file format chosen for Geoshare is similar to the Schlumberger DLIS format. In fact DLIS, Geoshare and the SEG RODE data formats all share the same underlying technology, the API's Recommended Practice 66 (RP-66) format. In a sense, the RP-66 standard could be thought of as a portable operating system for this whole family of data exchange technologies.
Geoshare works by defining a universal data model (much in the way that POSC and PPDM have done). A half link is built using an application's programming toolkit (API), or with a good knowledge of the application's internal data format, and writes data out of the application into the Geoshare data model. The reverse occurs when the data is read by another application. The use of the RP66 format, which takes care of the low level stuff, such as how floating point numbers are stored, means that a Geoshare data file can be written to tape, stored on disk, or even sent around the world using the Internet. The actual file structure is in two parts. First comes the Parameter Data. This describes the data to follow in the subsequent Frames - which contain the actual information. Data to be written to a single Geoshare file may contain 15,000 well logs, 17 Gigs of 3D seismic, and so on. Writing a Geoshare sender is said to be much easier than writing a receiver. Footprinting problems may be associated with the transfer into and out of the Geoshare data model.
For those who would like a fast track to building Geoshare half-links, Sumner's company, Independent Consulting Services provides a toolkit in the form of the GeoBasic product. This contains a wide variety of low-level building bricks for constructing Geoshare half links.
The one-day course offers an excellent introduction to the standard and I'm sure that if my livelihood depended on it, I could now be out there writing half-links along with the best of them. More info on the Geoshare course and GeoBasic from Bill Sumner on email@example.com.
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