Linked drawings are drawings that are created dynamically from geometry data stored in tables or created by queries. The table or query may be in the Manifold project or it may be a table or query in an external database provider. Linked drawings are shown in the project pane using an icon that include a yellow "database" cylinder to show they are created from a database table or query.
There are two types of drawings in Manifold:
· Regular drawings - These are static components in which all geometry (the information that defines the shape, size and location of objects) is stored in the drawing component with data associated with each object saved in the drawing's table component. Such drawings are also called local drawings.
· Linked drawings - Linked drawings are created from geometry data stored in database tables or generated from database tables by queries. Such databases and queries can reside within the Manifold project or, as is more frequently the case, they can reside in external database servers, so that even though the linked drawing appears to be a component in the Manifold project the actual data to create that drawing comes from the external database.
Linked drawings have characteristics depending on their source of geometry data:
· Linked drawings from geometry data - These are fully editable, read/write drawings containing points, lines or areas that are created dynamically from geometric columns in tables. Linked drawings can be linked from a variety of database technologies using a variety of different methods of storing geometry data. For example, drawings can be linked from geometry data saved in OpenGIS style Geometry(WKB) form, ESRI style Geometry(SHP) form or Manifold Geometry form in a very wide range of database products, such as Microsoft SQL Server, Oracle, IBM DB2, MySQL or even within ordinary Microsoft Access .mdb databases. Manifold also supports Oracle Spatial and Locator native databases saving geometry as SDO_GEOMETRY data. See the Geometry in Tables topic.
· Linked drawings created from queries - When linked drawings are created from queries, if the query creates geometry data on the fly then the resultant linked drawing will be read-only regarding spatial data such as the shapes and positions of objects (points, lines, areas).
· Linked drawings created from geocoded tables - This is a special case of linked drawing provided for the convenience of users when dealing with simple geocoded data in tables. When a geocoded linked drawing is created from a geocoded table, Manifold will automatically create an intermediate query that takes the simple, non-geometry data from the table's coordinate columns and then on the fly will create geometry data from which a linked drawing may be created. Geocoded linked drawings contain only points or lines that are created from X and Y (Longitude and Latitude) values saved in coordinate columns in database tables, that is, so-called geocoded tables. Linked drawings created from geocoded tables using coordinate columns are read-only and are provided as a convenience to simplify the acquisition and display of geocoded data in a variety of common applications. See the Creating Drawings from Geocoded Tables topic and the Linked Drawings from Geocoded Tables topic for details.
The above guidelines show the tremendous flexibility of linked drawings. However, even with such flexibility we should keep an eye out for logical limitations of various data sources from which drawings may be linked.
For example, linked drawings support adding or removing objects, provided the data source supports adding or removing table records. Suppose we have a table in our project that contains a geometry column. We can link a drawing to that table and it would be possible to add or remove objects in that linked drawing. Suppose now we create a SELECT query in that same project that takes geometry data and other columns from the table. We could also create a linked drawing from that query, but we would not be able to add or remove objects from that linked drawing because it is created from a query, which is a "one way" generator of geometry data.
The projection of a linked drawing is specified by its data source. Attempting to re-project a linked drawing will reload its data from the data source.
The View - Properties dialog for components shows the data source of a linked component (such as a linked drawing) and other relevant information.
The Link / Share dialog accessed from the [...] browse button for linked or shared components accessed from the View - Properties dialog will provide a summary of the link or share properties. This will show the status of a shared component and whether or not changes in a linked component will propagate back to the data source.
Linked Tables in Linked Drawings
Like any drawing, a linked drawing also has its own table, which in the case of a linked drawing is a linked table. Such linked tables are just like regular, standalone linked tables and can be used just like standalone linked tables.
For example, we can make changes in the linked table and those changes will be implemented back to the data source from which the table is linked. In particular:
§ A linked table allows adding or paste-appending a new column, renaming an existing column, and changing the type of an existing column.
§ We can change the design of a linked table.
§ It is possible to geocode records in a linked table.
All of the above capabilities apply to both standalone linked tables and tables bound to linked drawings.
Manifold will also try to exploit the capabilities of the remote data source whenever possible in the case of the linked tables associated with linked drawings. For example, if new columns must be created in such tables because objects are being pasted from other drawings Manifold will try to create such new columns as NULL-able (that is, able to contain NULLs).
Importing or linking a drawing from another drawing in the same .map project using the Geom (I) intrinsic field will inherit both the coordinate system as well as the location precision of the source drawing.
Creating Drawings from Geocoded Tables
Create a Linked Drawing from a Geocoded Table
Formatting Lines in a Linked Drawing
Geometry in Tables
Importing and Linking Tables
Linked Drawings from Geocoded Tables
Multi-User Editing of Linked Drawings
Project Pane - Open Data Source
Queries and Geoms
Spatial DBMS Facilities
View - Refresh Data