The Spatial Data Transfer Standard (SDTS) was designed to be capable of representing virtually any data model, rather than being a prescription for a single data model. It has fallen short of this ambitious goal for a number of reasons, which this paper investigates. In addition to issues that might have been anticipated in its design, a number of new issues have arisen since its initial development. These include the need to support explicit feature de® nitions, incremental update, value-added extensions, and change tracking within large, national databases. It is time to consider the next stage of evolution for SDTS. This paper suggests development of an Object Pro® le for SDTS that would integrate concepts for a dynamic schema structure, OpenGIS interface, and CORBA IDL.

Pigging of pipelines within the oil industry has been around for well over 100 years and has been used as the preferred (if not the only) internal method for cleaning, maintaining operational efficiency, data gathering and inspection for integrity management purposes. The benefits in carrying out routine "operational" pigging cannot be underestimated and operational pigging to remove water, wax, scale and other debris which is formed during routine operations whilst transporting crude oil and gas is paramount in maintaining the integrity of any crude oil and gas pipeline system. The build up of such debris is common whether the pipeline is offshore between production platforms, from a production platform to onshore or a totally land based pipeline. Similar problems are encountered to varying degrees dependent on pipeline size, location and type of the crude product being transported. Pipelines are normally designed for a specific maximum flowrate, this maximum rate is generally maintained on a "plateau" for several years of a field's life, during which routine pigging operation presents little or no real problem to the pipeline operator. The cleaning pigs which are used are generally designed for the "maximum" of "potential flowrate" which the pipeline is due to see during it's plateau phase of operation. This assumption, that these pigs will be suitable for the life of field operations, is common place with pipeline operators and as such there is a significant increase in the risk that pigs will become "stalled" on a regular basis or potentially "stuck" causing significant disruption to operation, production and in the worst case scenario a very costly subsea intervention. As can be seen from Industry Analysts¹ there will be a decline in overall oil production not just from the UK Sector but from the North Sea Basin and Europe as a whole. Therefore the need to understand pigging operations in "low flow" modes of operation cannot be stressed highly enough. Receiver 11. Launch Foam Pig 12. Check Pig Signallers and Pig Receiver 13. Launch Metal Bodied Recovery Pig

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