In the upper part of the Thematic Information tag some the the common metadata of the thematic attributes database are found, specifically the Update Period of the content and the Date of the content located to the left of the tag. To the right of the tag the metadata of the element selecte in the tree are displayed and edited. These metadata change as different elements of the tree are selected.
The elements' metadata change according to the type of element:
- REL file (principal or distributed)
- Structured Vector: principal table (DBF) and fields of the principal table
- Unstructured Vector
- Raster: modal propertis of the image and properties of each band
- Associated Tables (DBF or ODBC) and fields of the associated tables
Principal REL file
This is always the first element in the relational scheme since it is the file in which the metadata are described and the properties of the tables and the fields that form the cartographic database are also described. The REL file that accompanies the database and contains this information is the principal REL file.
The properties shown in the upper right part of the tag for a principal REL file are:
Metadata version
Relations table version
Distributed REL file
It is possible to link a cartographic database with an REL file (which we call a distrinuted REL file) instead of linking it directly with an associated table (only in REL4 format). This relation has the advantage that the properties and links of the fields of the table to which the links are made are not defined in the REL file but in the distributed REL file. This property is interesting if a single table is linked to more than one database (for instance a districts thesaurus) since in this case the table properties can be defined for all the cartographic databases without having to describe them repeatedly.
The properties shown in the right hand part of the tag for a distributed REL file are:
Relations table versionIt is possible to change the distribute REL file name using the funcionalities provided by the Manager.
2.2 Structured Vectors Metadata
Principal Table (DBF)
For structured vector files the principal table is in DBF format and the properties that are shown in the right hand part of the window define the structure of the table, a summary of the properties of the fields and the option to show the content of the table and to open it using MiraDades. The table is not shown by default in case the tables are very big which would slow down the display of the box. It is preferable to only perform this function when the user specifically requests it (by selecting the specific button for this).
The properties shown in the right hand part of the tag for the principal table are:
Table name: TAULA_PRINCIPAL
Number of registers
Number of fields
Character set
More information:
Last update
Graphical Field Identifier
Entity Field Identifier
Geometric and topological fieldsField list and some of their properties
Principal table field (DBF)
Name
Description
Type, Size and Decimals
Treatment of the variable
Units of the variable
Show units
Show in queries
Separator
Can be represented by symbols
Quality
2.3 Non-structured Vectors Metadata
Unstructured vector data are always in REL1 format and cannot have any associated tables. The only metadata entry that can be defined for this sort of database in terms of field properties is the attribute type which these vectors store (text, integer or real).
Multiband image
Rasters are treated in the same way as a table where the information on each band is equivalent to the information on each field of the principal table (for a structured vector). In single band images there is only one field of information.
The structue of the image is stored in its own metadata file. This indicates which bands form each multiband layer. It is possible to modify the structure of the database by adding or removing bands from this structure.
The properties shown in the right hand part of the tag for multiband images are:
Table name: GENERICA_PRINCIPAL
Number of bands
List of bands and some of their properties
Modal data of:Data type and Compressed file
Treatment of the variable
Units of the variable
Show units
NODATA present
NODATA value
NODATA Definition
Remember that for any specific item of metadata, the value shown as the multiband image value is only the mode of the values of the different bands that make up the image. This is interesting as it allows the metadata files to save the majority values only once (they are saved in the section refering to the information on the table) and then store all the specific values of certain bands that are different from the modal value. This allows both the saving of disk space as well as greater consistency in the data.
Band
In the case of raster databases the
possibilities and properties of the metadata stored depend on whether the
raster is in REL1 (doc) or REL4 format. Common to both formats is the
definition of the minimum and maximum raster values and the value and
definition of the background (NODATA) value.
For raster files in REL1 format relations
with associated tables cannot be defined as the old documentation file
only allowed the definition of the raster categories. If the raster had no
categories described it was treated as a continuous quantitative type
raster and in this case the value units entry would describe the
units of the field. But if the field was categorical then this entry would
be used for storing a general description of the categories (for example,
"Land use").
For this reason, the aspect of the
properties of the field of an REL1 format raster in the GeMM varies
according to whether the raster is a continuous quantitative raster or a
categorical one. In either case the REL1 format raster file cannot store
metadata refering to the separator, the use of symbols or whether the
field is visible and can be consulted (they always are). As for the field
quality, the position is the same as for the Spatial Reference System
error in REL1 format as the only value that can be documented is the
Value error quality measure.
In REL4 format rasters all the properties
of the bands can be defined:
Band
Channel
Band index (internal)
Name
Description
Data type and Compressed file
Treatment of the variable
Units of the variable
Show units
Show in queries
Separator
Can be represented by symbols
Quality
Minimum value
Maximum value
NODATA present
NODATA value
NODATA Definition
Radiometry
2.5 Related Tables Metadata (and their
fields)
The associated tables can be in DBF format or any other type of table connected via ODBC (Access, Oracle, etc.). The properties and the metadata that can be defined for an associated table and its fields are the same as those that can be defined for the structured vector principal tables and their fields.
Associated table
Table index
Table name
Number of registers
Number of fields
Character set
More information:Last modification
List of fields and some of their properties
Associated table field
Name
Description
Type, Size and Decimals
Treatment of the variable
Units of the variable
Show units
Show in queries
Separator
Can be represented by symbols
Quality