It often takes a bit of sleuthing to compile this information accurately: the world of web archiving recommends no official metadata structure — yet!
But Obama believes "that we can and should be able to preserve those capabilities while addressing the privacy and civil liberties concerns that are raised by the government holding this metadata," the official said.
The inclusion of synonyms for the free text search allows controlled description of the metadata via the official term name but flexibility in the search term that is used via synonyms.
Officials conceded the metadata retention would not assist in tracking many internet-based communications, but said it would allow intelligence agencies to continue to use telecommunications data that had become less available.
When the White House was asked to respond to Wednesday's disclosure, pertaining to the seizure of telecom metadata, officials defended "the practice as a critical tool for preventing terrorist attacks".
Over the last half-year, government officials have had to abandon several of their claims about the effectiveness of the metadata collection program.
In statements after the programme was disclosed, intelligence and government officials have stressed that the NSA does not collect the contents of US calls, only the "metadata", such as the numbers called, the duration and timing of the calls.
Obama administration officials insist that the metadata program is vital because it assembles a "haystack" that makes it possible for a computer search to extract the "needle" of evidence leading to the perpetrators of a terrorist plot.
Security officials indicate that the metadata can be used to "flag" an individual for closer investigation, but there is no clause that allows for the destruction of information regarding millions of innocent callers caught in the dragnet.
