ANÁLISIS DE ALTERNATIVAS
4.7 Intercambio iónico
Platform for Internet Content Selection (PICS) enables Internet users to filter the material they encounter while surfing the web. Users can accept or reject the material based on its ratings. This filtering allows parents, businesses, schools, or discerning individuals to block access to inappropriate and objectionable material. For the most up-to-date PICS information, see the World Wide Web consortium’s PICS web site . You need access to the Internet to reach this site. The
specifications published at this web site enable:
v People who publish information on the Web to rate and label their own
documents. These can be HTML files or other files that contain images, sound or animations.
v Independent rating services to rate and label documents published by other Web sites and to distribute the labels to whomever requests them.
v Internet users to use their browsers to request these labels and determine how to handle rated and unrated information.
How Web clients use PICS
PICS-enabled clients allow the users to determine which rating services they want to use and, for each rating service, which ratings are acceptable and which are unacceptable.
For example, a family might choose a rating service that rates documents according to their sexual content. the rating service might have a low rating for romance, a higher rating for passionate kissing, and yet higher ratings for more explicit sexual activity. The parents might decide that documents containing romance are the highest acceptable rating for their household. they would then configure their browser to reject all documents that are unrated or contain a higher rating from this rating service.
In another example, the Hi-Tek Systems Corporation could label its own
documents with a ″For Hi-Tek Use only″ and could equip all its employees with browsers configured to accept only documents with a″for Hi-Tek Use Only″ and could equip all their employees with browsers configured to accept only
documents with this rating.
There are several steps in this process. v The client sends a request.
When a PICS enabled client requests a document, it indicates in the request which rating services are of interest. For example, assume these parents had configured their browser to evaluate rating labels from The Best rating service. When their children click a link to an HTML document, the browser request would also ask for the rating labels that were assigned to the document by this rating service.
v The server sends a response.
Assume the PICS-enabled server has a copy of the labels the client is requesting. When the server receives the client’s request, it sends the labels along with the
requested document. However, if the server does not support PICS or does not have copies of labels from that particular rating service, it sends the requested document anyway.
v The client checks the server response first.
The client first checks to see if the requested rating labels are imbedded in the document (in the meta-information) or if they were sent along with the
document. Some clients might accept rating information that is embedded in the file. Others might require a separate label from a registered rating service and a guarantee that it was created by that service. If the client successfully finds the label information it wanted, it evaluates the rating and either displays the document or blocks it and displays a message.
v The client contacts the rating service, if necessary.
If the client does not receive the label information with a requested document from the server, it might send a subsequent request directly to the rating service asking for the label information for that document. This requires a second connection, which takes longer and can discourage future visits to that site. The browser waits until the label information is returned before it displays any data.
Using a rating service to rate your site
With the IBM HTTP Server you can store and serve rating labels for the documents you publish. If you choose this option, you will want to start by registering a third-party rating service.
Setting up a rating service
The web server also enables you to act as a rating service or label bureau by providing a means for you to maintain and distribute rating labels for your site or other web sites.
Setting up a PICS rating service and a PICS label bureau
Because many Webmasters will want their pages rated, you have an opportunity to provide a service to a large number of web sites.
v Content providers will contact your organization to request that you rate their Web site and provide them with the labels so that they will be able to serve the labels along with their Web documents.
v Clients will connect to your server electronically to request labels for pages they are attempting to view when they cannot get the label information with the requested pages.
The PICS configuration file provides you with the means to manage the labels for other Web sites and transmit them when requested.
The PICS specifications enable anyone to set up a rating service, define the criteria by which they rate Web sites and documents, and then provide the ratings. With PICS support, you can establish your server as a rating service and maintain and distribute labels for other web sites. You can rate documents at a Web site
individually or use wildcard characters to quickly assign the same rating to all or part of a site’s offerings. You will need to create these labels and your own RAT file, you can use the PICS configuration file to manage these labels from a central point. Your server will then be able to automatically send the rating labels you have assigned when a client requests them.
If a Web site that you have rated requests the labels for their pages, you can also provide them with all their current ratings. Unfortunately, the World Wide Web Consortium has not yet defined a standard for the label bureaus or rating services to send a Web site all their label information. This means that the method for this exchange will have to be determined by the rating services and the web site that asked for them.
This task allows you to configure your server as a Platform for Internet Content Selection (PICS) rating service. You will need to define a rating system and create your own RAT file. Check the World Wide Web Consortium’s PICS specification
for instructions on how to do this. It includes the syntax for the
machine-readable format of the RAT file. You will also need to specify a URL for PICS-enabled clients and servers to use when they use their browsers to contact your server for labels. The default setting is internal which means the labels are stored on your server. This setting provides the best performance. You need access to the Internet to reach this site.
Use the Configuration and Administration forms to register your own rating service.
1. Click Configurations.
2. Click PICS Local.
3. Click Register your own rating service.
4. Complete the Register your own rating service form that is provided.
5. Click the Apply button.
You will receive a message that tells you whether or not the task completed successfully. Then, you may want to create a PICS label.
Maintaining your PICS rating service and label bureau
This task allows you to manage PICS labels for other web sites from a central point and serve them when clients request them. You can add, change, and delete the label entries that associate specific documents or pages with your rating labels. Use the Configuration and Administration forms to maintain PICS label entries for other Web sites.
1. Click Configurations.
2. Click PICS Local.
3. Click Maintain PICS label entries for other Web sites.
4. Complete the Maintain PICS label entries for other Web sites form that is provided.
5. Click the Search button and the Selected PICS label entries for other Web
sitesform shows your search results.
6. Complete the Selected PICS label entries for other Web sites form.
7. Click the Apply button.
Creating a PICS label
If you decide to act as a rating service, you will need to create PICS files. When webmaster’s contact you and ask for a rating you will send them these files.
PICS label extensions
The IBM HTTP Server has added extensions to save repetitious data entry and to allow you to add comments.
Comments for your own use
You can insert comments for your own use into label files. Begin these comments lines with #. Lines beginning with # are not sent to clients. This type of comments is an addition to the comment statements used inside labels, which are sent to clients.
Additional variables
You can insert the following variables in label files: v %%URL%%
The current URL will be substituted for this variable. When the server receives a request for a rating label that contains %%URL%%, it replaces this variable with the correct for statement before sending the label.
Note: Do not use this variable on generic labels (those that apply to multiple files).
v %%SERVICENAME%%
The service name requested will be substituted for this variable. When the server receives a request for a rating label that contains
%%SERVICENAME%%, it replaces this variable with the correct service statement before sending the label.
Use the Configuration and Administration forms to create a PICS label.
1. Click Configurations.
2. Click PICS Local.
3. Click PICS labels for your own rating service.
4. Complete the PICS labels for your own rating service form that is provided.
5. Click the Apply button.
You will receive a message that tells you whether or not the task completed successfully.
You need to store all your Platform for Internet Content Selection (PICS) rating labels in a threadsafe integrated file system on your server. The system stores each rating label in a separate file.
After you have created PICS files you may want assistance Maintaining your PICS files
Registering third-party rating services
Use this task to register the third-party rating services whose Platform for Internet Content Selection (PICS) rating labels your web site will use.
Any individual or organization can offer content labels for information on the Internet and serve as a rating service. You can use your server to start a rating service and label bureau. Whether you use a rating service or act as your own rating service, you’ll work with label files and rating files. Label files usually carry the .lbl extension while rating files carry the .rat extension.
Before you can register a rating service, you must have a copy of its RAT file stored on your server. The RAT file describes the rating system and provides the identifying URL for the service. You also need to get the rating labels from the
third-party rating service. You may be able to retrieve these automatically using the Request Label Entries from Third-Party Rating Service form.
Use the Configuration and Administration forms to register a third-party rating service.
1. Click Configurations.
2. Click PICS Third-Party.
3. Click Register third-party rating services.
4. Complete the Register third-party rating services form that is provided.
5. Click the Apply button.
You will receive a message that tells you whether or not the task completed successfully. You may want assistance requesting PICS labels after you’ve set up the rating service.
Requesting PICS label information
Perform this task to request label entries from a third-party rating service.
If the third-party rating service has a Domino Go Webserver or IBM HTTP Server, you can electronically request rating labels for all the documents on your Web site that the third-party service has rated. You will receive both rating labels and PICS configuration file label entries as a response to your request. Both types of
information are automatically stored on your server in the directory that is specified on the form.
The directory must exist, and you must authorize the server authorized to write to that directory. If the third-party rating service has not rated your Web site, it will return a response that indicates that it does not have the information you
requested.
Note: For a faster response time, rating labels for your site should reside at your site. That way the your server doesn’t have to call the rating bureau’s server to fulfill the request for rating information, instead it can supply the rating information from it’s own copy of the label file.
Use the Configuration and Administration forms to request PICS label information.
1. Click Configurations.
2. Click PICS Third-Party.
3. Click Request label entries from third-party rating services.
4. Complete the Request label entries from third-party rating services form that is provided.
5. Click the Apply button.
After you request the labels you might want assistance managing the PICS labels.
Managing PICS labels
In general, a label file is a text file that contains a label. Labels for a Web site can be:
v Self-assessed according to your own criteria.
v Self-assessed according to published criteria of a voluntary rating service. v Assessed by a third-party rating service according to the service’s criteria.
Once the ratings are established, you use label information to create
PICS-compliant rating labels, store the labels in the ″root″ (/) file system, and use the PICS configuration file to manage and transmit them. You will need to store both the RAT file and the rating labels in files on your server. The RAT file should be available from a rating service’s Web site. The rating labels must be stored one label per file.
Let the system automatically store the transmitted rating labels and RAT file and update your PICS configuration file for you. You can only do this when
electronically requesting labels for a third-party rating service that has a Domino Go Webserver-based Web server
You can use any directories, subdirectories, and file names that make sense at your site and for your implementation. We recommend that web sites have a separate directory or subdirectory for each third-party rating service that they use. This is required for automatic updates when requesting labels from rating services that have the Domino Go Webserver of the IBM HTTP Server.
Our examples use a file extension of .lbl on each rating label file. This is also the extension for any label files the server transmits electronically.
Managing PICS labels for your own web site
Follow these steps to store rating labels in your file system and configure your server so it sends these labels when clients request them.
1. Obtain a copy of the RAT file from the rating services you want to use and store it in your file system or your server.
2. If you are getting rating labels from a third-party rating service that has Domino Go Webserver or the IBM HTTP Server use the on-line Configuration and Administration forms to request the labels and the entries for your PICS configuration file electronically. When you receive these files, your server will automatically be updated for you.
If you are not getting rating labels from a third-party rating service that has the Domino go Webserver or the IBM HTTP Server.
v Obtain the ratings from the third-party rating service or rate your own documents.
v Create labels according to the format published in the PICS specification. v Store the labels in separate files, one label per file, in your server’s file
system.
v Tell your server which documents are rated, where the actual rating labels can be found, and which rating service provided the labels. You do this by adding entries to the PICS configuration file to associate the rated documents with their label files. You can use the on-line Configuration and
Administration forms to update and maintain this file or you can edit it manually.
Managing PICS labels for your Web site in each document
You can edit your HTML files and embed PICS ratings information in the meta element of the document header. This process is entirely manual and therefore time-consuming, error-prone, and difficult to maintain. Because the header is a part of the HTML file, you can’t include non-HTML files such as images. It does not incorporate any security mechanisms (message digest, digital signature, and so on) to guarantee label validity. This may be important to the requesting client. The
PICS specification explains how you can embed rating information in each document. You need access to the Internet to reach this site.
Managing PICS labels for your Web site from a central file
The Web server’s PICS support allows you to store the rating labels for all the documents on your Web site and manage them from a central file. The server sends labels along with your Web pages when a client requests them.
In addition to the rating labels, you must also have a PICS-compliant rating system description file that describes the rating system used to rate your documents. These are called RAT files, usually have a .rat extension, and rating services will provide them along with their labels.
Use the Configuration and Administration forms to configure label entries for your Web site.
1. Click Configurations.
2. Click PICS Third-Party.
3. Click Maintain PICS label entries for your Web site.
4. Complete the Maintain PICS label entries for your Web site form that is provided.
5. Click the Search button.