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CONCEPT OUTLINE
The basic assumption made for the study has been the feasibility of its execution. Many times we have encountered solutions, which - although theoretically possible, in practice have not been suitable for execution (e.g the daily updating of IPE).
Another assumption has been to build a system based upon the Internet. Internet network is the fastest developing part of telecommunication infrastructure, and is the 'blood supply system' for all electronic information. At present, Internet is provided with mechanisms making the exchange of information completely safe.
The basic feature of the solution is being based upon services provided by individual nodes of the data infrastructure. Where it has been possible, ISO or OGC standards have been used, which applies in particular to WMS/WFS services.
The concept based upon making services available entails that lower rank nodes will not send data to upper rank nodes, but that upper rank nodes will extract data from the lower rank. This is a substantial change in the approach to the construction of a complex system of servicing the geodetic infrastructure of our country.
Generally, the principle has been assumed that maps will be downloaded by customers in the raster form (WMS format). Vector data (WFS format) could be downloaded by specialized nodes, for the purpose of analyzing or processing them, e.g. for the purpose of plot location service execution, updating of buildings in TBD, updating of PRG borders, or preparation by a specialized map node in various formats. The map distribution service, that is the WMS service, has been divided into two categories:
- the service of providing access to public data,
- the service of providing access to non-public (protected) data.
The data made available via the service included in category one make up the basis of the GEOPORTAL, and because they are publicly available, much interest in them can be expected. These data will be stored at various levels (district/county, province, central one). To provide the required efficiency, distribution directly from the places, where the data have been generated.
The user of GEOPORTAL, when viewing a map, will be at the same time using central data (e.g. administrative borders, ortho-photomap), and district/county data (e.g. borders of plots, address points). It is possible, because the WMS service assumes the possibility of making transparent rasters and their mutual overlaying.
Category two concerns data with limited access. Access may be restricted both regarding areas (e.g. to one entire register unit), and topics (e.g. exclusively to water supply network).
Because the problem of authorization and access control is a complex process, the concept has assumed the existence of special servers proxy. For central data, this will be the Central Server Proxy (CSP), while for data in provinces and districts/counties from the area of a given province, this will be the Provincial (Voivodship) Server Proxy (WSP).
Servers proxy do not generate data. They play the role of filters, which on the basis of the query made by the user and the users authorities will either allow, block, or allow with modification the transmission of the query to the proper data server, being part of:
- a cadastral node,
- a topographic node,
- a general geographic data node.
In general, the activity of a server proxy will boil down to the analysis of queries and their rejection or suitable modification (for example, removal of a specific layer from the WMS/WFS query) before passing the query to a cadastral or topographic node.
The above is worth stressing, as from the economic point of view it is of much importance that the servers distributing data (providing services) with restricted access do not have to deal with any user authorization. All they need to do is check, whether the query came from the correct server proxy. It results from the data distribution manner described above, that data with restricted (protected) access will be always sent via servers proxy.
Simplified implementation scheme
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