/ Copying of GDB components / Chapter 50. Operations of copying

GDB components and their interconnections

Arrangements for operations of copying of different GDB components are organized in such a way that the corresponding procedures were more or less uniform, depending on the type of copied components the less the better. However, copying of composite GDB components such as maps, layers and themes demand understanding of their structure and interconnections with other GDB components.

For example, let's examine what a map consists of and with what GDB components it is linked.

A map consists of layers. On the basis of a map themes having the structure similar to map structure can be built. A map layer contains features belonging to one of the layer types. Tables can be linked with every type, queries can be built on the basis of tables. Tables contain records which, in their turn, can be linked with layer features. Styles from libraries are used for specifying displaying style of every map layer and every feature type of the layer, and also specific styles of features and styles used in themes. That is why when copying a map it is necessary to copy not only map layers containing features, but linked tables, queries and displaying styles used in the map and its components.

Thus, before passing to a detailed examination of operations of copying composite GDB components it is required to have a look at GDB components and their interconnections taking into account peculiarities of copying operations (chapter 3 “GDB Structure”, chapter 9 “Map structure”, chapter 23 “Table structure”, chapter 32 “Links between maps and tables”, chapter 78 “Editing styles”).

In table 50-1 generalized GDB structure is presented. The symbol “…” (dots) in the table row denotes that arbitrary number of components is possible.

Table 50-1. GDB components

GDB contains: maps; themes built on the basis of maps; tables; queries built on the basis of tables; layouts; library of displaying styles, list of users.

A map is determined by a name and parameters (base point, range, partition) and is made up of layers. On the basis of a map themes can be built.

A layer is determined by a name and partition. A layer contains features. All features in the layer are divided into types. Default displaying style of features can be specified for a layer.

Feature type of layer is determined by a name, spatial category and tables linked with the type. For a type default style of displaying features belonging to the type can be specified.

A feature always belongs to one of the feature types of the layer and can have a specific displaying style. A feature can have links with records of the tables which are linked with the feature type.

A theme is usually built on the basis of one or several maps. It is determined by the name and displaying parameters (center coordinates, sizes and slope angle of the displayed region, background style, coordinate grid) and consists of layers. A set of theme layers is a subset of layers of the base map. Besides, a theme can comprise work layers which does not belong to any map.

A theme layer is one of the layers of the base map (the map on the basis of which a theme is built) and has the same name as the layer of the base map. Displaying style substituting the layer style of the base map can be specified for a theme layer. A set of types in the theme layer is a subset of types of the corresponding layer of the base map.

A feature type of the theme layer is one of the types of the corresponding layer of base map and has the same name as the type in base map layer. A set of tables linked with theme feature type is a subset of linked tables of the corresponding map type. Displaying style substituting the style of the type of base map can be specified for a theme type. It is possible to specify for a type a filter for which specific displaying styles can be set. When specifying a filter one can use tables linked with theme type and queries based on them.

A table is determined by a name and fields. A table contains records. Each field is determined by a name, a type and attributes.

A query is determined by: a name, base tables (a query can be built on the basis of several tables), fields, join scheme of base tables, search condition, a method of sorting records, indication of removing duplicated records, calculation condition. A query field corresponds to the field of one of the base tables (or it is determined as a calculated one) and is characterized by width.

Now let's look at components from a different point of view. Every GDB component is characterized by a certain structure (description) and contents (filling).

Table structure is understood as description of its fields each of which is characterized by a name, type and attributes. Table records are contents of the table.

Structure of a feature type of a map layer is specified by a spatial category, default style of displaying features of the type and links between the type and tables. Features belonging to the present type and links between these features and table records can be considered to be the type contents.

Layer structure is characterized by description of types of the layer each of which has a name and its own structure, by partition and default style of displaying features. Features of the layer and links between these features and table records are the contents of the layer.

Map structure is characterized by description of layers each of which has a name, its own structure, and the following parameters: base point, range, partition. Features of map layers and links between these features and table records are the contents of the map.