SAS

A service advertisement service--a service which allows netlets to be downloaded and hence allows service binding.

More correctly, it allows the downloading of netlet descriptors and corresponding unsigned arguments. It may use the HTTP protocol, but other options are possible which allow, for example, negotiation for the most suitable netlet.

Since any netlet descriptor will probably contain references to the JARs it needs (rather than containing the JARs themselves) a SAS will most likely also deliver JAR files.

Figure: Using a service advertisement service (SAS). (1) A developer uploads their service to the SAS. (2) In return they get the URLs of bind servers which they put into warrants for their service. (3) & (4) A consumer netlet uses such a warrant to bind to the developer's service.

Access to a SAS is likely to be in three ways:

• The owner of the SAS will have administration access to it. They will be able to create contracts with customers and issue them with user warrants.
• A SAS user will use their warrant to upload netlet descriptors, unsigned arguments and JAR files. With each upload they will get in return a list of bind servers (i.e. URLs) where the uploaded items are now available. They can then incorporate these bind servers into warrants for their newly-uploaded service and pass on these warrants to their service consumers.
• A service consumer will present a warrant to its node which will then bind the service from the SAS. It will use the SAS because the warrant lists the bind servers where the service is available.

See Figure  for the second and third of these.

See also: binding protocol.