The inclusion of the theses is compulsory since 2012 due to a change in Spanish legislation (article 14.5 of RD 99/2011). Before that inclusion was voluntary.
TDX goals are:
The theses included on TDX are described with Dublin Core metadata and use the interoperability protocol OAI-PMH (Open Archives Initiative-Protocol for Metadata Harvesting), which increases visibility when offered together with other repositories.
According to Spanish legislation, thesis must be published in digital format in an institutional repository. The Declaration by the author, the file of the thesis and the file with abstract a keywords will be used to do this publication.
When you deposit the thesis, you must also sign a Declaration by the author. Some highlights:
If the thesis is affected by technology transfer or protection issues (patents, confidentiality agreements, etc), the author must contact his/her department before the thesis' deposit. A special procedure might be necessary.
The integrity of the text if guaranteed by applying PDF security options.
According to Spanish legislation the thesis must be published in digital format in an institutional repository. However, the regulation can be adapted for specific cases duly justified. See:
UPF regulations require the institutional repository to be TDX.
All these regulations are embodied in the Declaration by the author and the procedure for publishing thesis in TDX.