In training (asker) Jul 31, 2009:

It's true, that's why I'm gining a new sentence. The document refers to debt rating; so I think this a better example of the term I'm looking for. Many many thanks Alejandro.

Alejandro Alcaraz Sintes Jul 31, 2009:

Context But the context in this second example seems different. I interpreted it as a pledge by the school authorities to fight violence in the school, bullying...
I may be wrong, but that's my interpretation in the scant context provided, to use Rirchard Boulter's words.

In training (asker) Jul 31, 2009:

Security Pledge I found another sentence having the same term: The wide array of structures has led to debt being issued under a variety of security pledges.
I think that in this context "medidas de seguridad" does not apply...