The PD system allows one to integrate programs and their documentation in ASCII files. Such a program with documentation file (PD file) consists of alternating documentation and program sections. PD files can be compiled directly; for a compiler, documentation sections are just commentaries to be ignored. On the other hand, the PD system allows one to transform PD files into LaTeX source files and so to produce formatted documents. For the description of formatted material in the documentation sections, a simple markup language is offered. The main goal in the design of this language is readability of the source text. In other words, formatting specifications are kept as ``implicit'' and ``invisible'' as possible and much of the ``formatting noise'' occurring in LaTeX and other markup languages can be hidden. PD files should be readable for anyone without prior learning of the markup language.
Independent from the problem of documenting programs, PD files may be convenient for describing text documents in ASCII files (rather than using LaTeX directly). The PD System was written in C using the lex and yacc tools. It includes its own documentation as a PD file.
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Abstract. Recently there is much interest in moving objects databases, and data models and query languages have been proposed offering data types such as moving point and moving region together with suitable operations. In contrast to most earlier work on spatio-temporal databases, a moving region can change its shape and extent not only in discrete steps, but continuously. Examples of such moving regions are oil spills, forest fires, hurricanes, schools of fish, spreads of diseases, or armies, to name but a few.
Whereas the database will contain a "temporally complete" representation of a moving region in the sense that for any instant of time the current extent and shape can be retrieved, the original information about the object moving around in the real world will most likely be a series of observations ("snapshots"). We consider the problem of constructing the complete moving region representation from a series of snapshots. We assume a model where a region is represented as a set of polygons with polygonal holes. A moving region is represented as a set of slices with disjoint time intervals, such that within each slice it is a region whose vertices move linearly with time. Snapshots are also given as sets of polygons with polygonal holes. We develop algorithms to interpolate between two snapshots, going from simple convex polygons to arbitrary polygons.
For more information, download the Paper:
E. Tøssebro and R. H. Güting:
An applet demonstrating the algorithm and the source code for download is available here.
Some documentation of the algorithms behind the applet can be found here.
Download Slides for book Moving Objects Databases
Letzte Änderung: 2018-08-30 (HHH)