To account for the latter case, the server may respond with missing authorizations, and request the browser to repeat the request, now with the missing cookies (presumably, covered by the just discovered authorizations).
In our model, however, the client may contact the DNS to retrieve the missing authorizations.
Prior to sending the user's request, the browser looks up missing authorizations (if any) in the DNS.
Send the user request, allow the server to provide any missing authorizations, and then resend the request again.
If purpose compliance is satisfied for at least one policy, the process continues, otherwise it is immediately blocked due to the missing authorizations.
Our proposal provides three mechanisms to discover all applicable authorizations: Send a preflight request to the server Send the user request, allow the server to provide any missing authorizations, and then resend the request again Perform a DNS lookup.
The sequence diagram for an XDC cookie-reading scenario is shown in Figure 4. Before sending XDC cookies to the server the Web client needs to find all missing authorizations.
Our Web server may respond with the missing Xdc-Authorization headers and set the HTTP status code to XDC_RESPONSE_REQUESTED, a value we introduced.
Finally, an Xdc-Options header may include additional XDC processing instructions; currently only the dns-max-age option is defined; if set, it instructs the browser to look up missing XDC authorizations in the DNS and defines the maximum frequency of such lookups.
Such authorization is missing from the United Nations Security Council resolution passed last week, and so far there is no movement in the Council to toughen that resolution.
A few assessments (8) could not be used due to missing data, and 99 assessments involved no authorization for PCS services.
