The Quatro Proxy
QUAPRO is a server-based application that processes two types of request concerning a given URL:
- Does the site carry any labels and, if so, what type(s) of labels are present?
- Is the label authentic?
Communication with Quapro is carried out using the Simple Object Access protocol (SOAP) with output available in text, RDF and HTML formats.
The authenticity of each label is determined using three controls: date control, hash control, content analysis control.
a) Date control
When an authentication request is made to an LA, it will return a true or false flag to indicate whether the current date and time is within the validity period of the label. The definition of that period of validity is entirely in the hands of the labelling authority but is typically a year after the label was first issued.
b) Integrity control
Each label detected by Quapro is hashed and the resulting digest is passed to the LA with the authentication request. This can be compared with an equivalent data point in the LAs database if the LA chooses to operate such a check.
c) Content analysis control
A resource is forwarded to a content analyser application (e.g. FilterX). The automated analysis is then compared with the label and an error is raised if the two differ widely.
As can be seen, the first two checks are used to authenticate the label against the LA’s database, whereas the third check compares label’s description against the content of the corresponding resource. Not all checks need be used by each LA. The final result of the analysis is one of: valid, invalid, or ‘cannot be verified.’
The processing steps of QUAPRO
- The QUAPRO steps, from the moment it receives the URL(s) until its response, are as follows:
- QUAPRO receives an array of URLs (if single URL, array of size 1). QUAPRO always processes URLs one-by-one.
- QUAPRO visits a URL and looks for a link to an RDF file. Such a link may be found either as an entry inside the http header or as an html link tag.
- In any of the following cases
- no link to an RDF file is found,
- there is a link to an RDF file but this file is not accessible,
- there is a link to an RDF file but this file contains no quality labels,
- When there is an RDF file which is accessible and does contain content labels (it is a RDF-CL file), this file is retrieved and parsed by QUAPRO. QUAPRO identifies the LA(s) in the label(s) and replies to the original agent which label from which LA is found.
- QUAPRO contacts then each LA’s database (via DAcc) taking into account that the following cases are possible:
- The RDF-CL file is stored on the labelled site AND the content label can be edited by the site admin/owner,
- The RDF-CL file is stored on the labelled site BUT the content label cannot be edited by the site admin/owner,
- The RDF-CL file is stored on the LA database, which means that the content label cannot be edited by the site admin/owner.
- When the LA has specified, inside its content label schema (in the tag “contentAnalyserURL”), the URL of a content analyser, the resource HAS TO be forwarded to the content analyser for the content analysis control.
- A synthesis of the results of the date, hash, and content checking (if all of them are available) gives the final validity value of a label.
- Finally, QUAPRO returns a relevant SOAP message
The full technical detail of the messaging used by QUAPRO is published in the accompanying .(NB. A link tag in header for this page should point to the WSDL doc as an alternate representation of the page.)