T. Hadzilacos and N. Tryfona, "Logical Data Modeling for Geographic Databases," Int. Journal on Geographical Information Systems (IJGIS), 1996.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... 2) The previous example on the map of states shows a feature that frequently occurs in GIS applications, namely the possibility of representing a composition of objects (e.g. a state is composed of counties) In the GIS area, it is only recently that object composition has received attention [6, 7]. The example above also illustrates the similarity with statistical databases [8] where a major problem is to define proper mechanisms for data aggregation (across many dimensions) According to [9] a database is a statistical database if it contains the following three kinds of data: ....

....of interest are regions within the space; attributes (such as temperature or elevation) are associated with them. In the latter case, the primary objects are geographic entities with which is associated a spatial attribute. Recent work has been done to integrate both approaches, as for instance in [14, 7]. These approaches are based on a mapping of conceptual geographic models onto geometric Section 2. A Conceptual Geographic Model 4 layers. The model proposed in this paper belongs to the latter category, hence we focus on conceptual geographic entities. This section starts with a description ....

T. Hadzilacos and N. Tryfona, "Logical Data Modeling for Geographic Databases," Int. Journal on Geographical Information Systems (IJGIS), 1996.

.... The previous example on the map of states shows a feature that frequently occurs in GIS applications, namely the possibility of representing a composition of objects (e.g. a state is composed of counties) In the GIS area, it is only recently that object composition has received attention [Wor94, HT96] The example above also illustrates the similarity with statistical databases [Mic91] where a major problem is to define proper mechanisms for data aggregation (across many dimensions) According to [Len93] a database is a statistical database if it contains the following three kinds of data: ....

....are regions within the space; attributes (such as temperature or elevation) are associated with them. In the latter case, the primary objects are geographic entities with which is associated a spatial attribute. Recent work has been done to integrate both approaches, as for instance in [GS93b, HT96] These approaches are based on a mapping of conceptual geographic models onto geometric layers. The model proposed in this paper belongs to the latter category, hence we focus on conceptual geographic entities. This section starts with a description of our base complex object model. We then ....

T. Hadzilacos and N. Tryfona. Logical Data Modeling for Geographic Databases. Int. Journal on Geographical Information Systems (IJGIS), 1996.

....semantic and object oriented models (see [18] 20] spelling out the details for ER is significant in showing the generality and practicality of our approach. This work builds on (a) classic and recent research on conceptual modeling by using ER [5] 14] 16] b) the study of spatial needs [8][10][22] and (c) previous and theoretical research on the subject at CTI [17] 18] 19] Its contribution starts with the identification of the particular needs of geographic applications which are not adequately served by ER (Section 2) The main goal is the satisfaction of these requirements ....

....and used extensively by others shows that the problem has not yet been solved and a deep understanding of semantics of space has to precede. 2. What is special about Geographic Conceptual Modeling Modeling geographic applications entails tackling of specific and unique problems [4] 8][10]. These include the duality of objects and fields, reasoning with incomplete information in several forms such as indeterminate boundaries, fuzzy geographical phenomena, imprecise measurements, scaling and map generalization, spatial relationships, and technical issues such as raster vs. ....

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Hadzilacos, Th., and Tryfona, N., 1994, Logical Data Modeling for Geographic Databases, IJGIS (10,2).

....background; and OMT as a representative of the Object Oriented family. We present the way we handle the six geographic peculiarities of Section 2 by using (extending or specializing) each one of these three models 1 . b) At the phase of logical geographic database modeling we extended [Hadzilacos and Tryfona, 1994] the mathematically sound relational model with the aspects of geometry and time. Here, we argue why the relational model is good to serve as a basis for an extended model to accommodate spatial needs, but not good enough as a stand alone solution. 4.1 Evaluation of conceptual data models for ....

....Dimensional) region (2 Dimensional) or combination there of) The former is modeled with concepts like layers whereas the latter is modeled with concepts oriented towards objects. Couclelis, 1992] offers an insightful view on the orthogonallity of the two approaches. The GeoRelational Data Model [Hadzilacos and Tryfona, 1994] is an extension of the relational. It provides a language for the definition of relations (used for non spatial entities and relationships) of layers (to represent space dependent attributes) of object classes (to represent geographical entities that have characteristics from more than one ....

Hadzilacos, Th., and Tryfona, N. Logical Data Modeling for Geographic Databases, International Journal of Geographical Information Systems Vol. 10, No 2. (1994).

....(rasters) and standard data (e.g. text, numbers) To handle data at this level, many types of conceptual models exist which are either based on an entity viewpoint or on a space viewpoint of the data. We do not elaborate on this here. For information about such models the reader is referred to [HT96, Wor94] In order to give the reader an insight into such a model, below is a simplistic entityoriented conceptual model for (vector) maps. The main objects are of type map which are composed of geographic objects. Each such object has two parts, an alphanumerical one (or description) and a ....

T. Hadzilacos and N. Tryfona. Logical Data Modeling for Geographic Databases. Int. Journal on Geographical Information Systems (IJGIS), 1996.

....(rasters) and standard data (e.g. text, numbers) To handle data at this level, many types of conceptual models exist which are either based on an entity viewpoint or on a space viewpoint of the data. We do not elaborate on this here. For information about such models the reader is reported to [HT96, Wor94] In order to give the reader an insight into such a model, below is a simplistic entity oriented conceptual model for (vector) maps. The main objects are of type map which are composed of geographic objects. Each such object has two parts, an alphanumerical one (or description) and a ....

T. Hadzilacos and N. Tryfona. Logical Data Modeling for Geographic Databases. Int. Journal on Geographical Information Systems (IJGIS), 1996.

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