SPECIAL FEATURES OF THE UNIVERSAL GEOSPATIAL METADATA MANAGER (GeM+)
The aim of GeM+ was to create an application that would be easy to use. Since the documentation of metadata is already complex when generating and maintaining maps, the use of the application ought to be as intuitive as possible. For this reason a dialog box design was chosen with central tags and with primary importance given to the help provided for the user.
The central tags allow a quick overview of all the aspects (sections) that can be documented in relation to a cartographic database. It is therefore a very useful tool because it allows a lot of information to be organized in a structured way. Another of the interesting features of the tags is that the users are accustomed to using them (in Windows 95 and later versions of Windows) so that they already know how they work. An example of this is the way in which changes can be made in one tag which are automatically saved in memory when switching to another tag (without having to specify that they be saved), but it is necessary to save the changes explicitly (in the main dialog box) in order to save the changes in the hard disk. Similarly, it is important to be aware that this action (clicking on the save button) will save all the changes made in all the tags and not just the visible tag.
The help plays an important role in a metadata program since it has to inform the user of the meaning of all the keys that make up the metadata as well as how to specify these keys, where to find the information that they are looking for, etc. The help provided with the program has two main parts.
Firstly there is a fast and simple help that appears automatically when the cursor is placed over each of the tags. This gives a short explanatory text about the content of each section to indicate to the user which section to go to in order to document a specific aspect of the database.
Secondly it is possible to access the compiled help document of GeM+ (in CHM format) from points within the application ("help" buttons or "?"). This help contains explanations of the content and the characteristics of the various entries in GeM+, together with their equivalences in the REL file, where the metadata are stored (with a section-key structure), in various metadata standards, and in the older documentation files.
Structure and operation of GeM+
GeM+ allows the metadata of a layer to be consulted, edited or, for layers without metadata, created.
Edit Metadata: On opening GeM+ it is necessary to decide which layer is to be edited. The user may choose the name of a layer, the name of an REL, or the name of an older documentation file. Once the metadata to be edited have been selected they are read from the REL file (if the layer has no REL file, in version 4 this information is read from the older documentation files)
Create Metadata: When openning GeM+ it is necessary to select the name of the layer to be documented. It is possible to generate a metadata file for images or unstructured vectors which lack previous documentation (such as I.rel/J.rel, or doc/dvc files respectively). The user will be asked whether they wish to generate the metadata for the file. If they select yes then they will be prompted to fill in some minimum metadata from which they will be able to continue to document the database.
In both cases a structure is saved in memory with all the information. When the GeM+ dialog box is viewed all the elements of the metadata structure are shown as needed. Each of the tags shows the information about one of the sections of the metadata.
On changing from one tag to another the information that the user has introduced is saved with this structure. Should it not be possible to do this (for instance, because the format or the content of some of the fields is incorrect) a message is issued informing the user of the problem. To avoid loosing information the tag cannot be changed until the problem is resolved.
Finally, once all the desired changes have been made, the user may save the metadata in REL4 or REL1 formats. (REL4 is recommended). For raster data it is possible to keep both formats at the same time (it is possible to have information in the *.doc and *I.rel files). If the cancel button is selected in the GeM+ main dialog box then the application is closed without saving the changes made.
What type of information may be documented?
GeM+ calls Base (or cartographic database) a layer, a map series or a MiraMon map. In this context "base" is equivalent to 'geographic dataset'. The first version of GeM+, only allows layers to be documented. It is planned to extend GeM+ to include series and maps in the near future.
Where appropriate, a layer may contain various bands (multi-band layer), each of which provides information on different features of the same territory. For example, the layer "Satellite image of the Alt Emporda area (12 July 1982)" could contain a number of bands corresponding to the spectral bands of the satellite sensor used to acquire the image, whilst the layer "Digital Terrain Model of the Eastern Pyrenees" would contain bands for the related digital models (height, slope, orientation, etc).
The data of the different bands in a multi-band layer can be in individual files (e.g. The seven IMG files of a Landsat-5 TM image, or in a single file containing all the bands grouped together (e.g. in a JPEG 24 bit colour format, which contains 3 bands, JPEG2000 format, MrSID format or in the BIL, BSQ formats used in remote sensing for storing multi-band images).
The keys and sections that are shown in bold type in the help are obligatory. In some cases they are conditional, for example, there are keys that are only obligatory when information is entered on the section to which they relate (which itself may be optional). Another more obvious example are those keys that are obligatory depending on the type of layer that is being documented (for example, the input File Name is only obligatory for multi-band layers).
Metadata files: supported formats
GeM+ reads metadata from older documentation files and from REL4 format relation and metadata files. For more information on these formats see the database metadata and table relations file formats.