PadSpace: A software architecture for the ad hoc federation of distributed visual components and Web resources

In this paper we will propose an extension of a typical Linda-like coordination model (tuplespace) to provide mechanisms for the cooperation of Web applications, Web services and end users' local resources. This new model assumes that all these different types of resources are wrapped into visual components called pads before their cooperation. Pads are defined based on the meme media architecture. This new Linda-like coordination model is called a PadSpace. A PadSpace uses an XML-tuplespace as its core coordination model. The XML-tuplespace is a distributed coordination model that extends the Linda coordination model with the ability to carry XML documents in tuple fields. We call each tuple an XML-tuple. A PadSpace uses the 2D meme media system IntelligentPad as its platform. Linda represents all the available services as tuples and stores them in its tuplespace. It also represents each service request as a tuple, and matches this requesting tuple with a compatible registered tuple representing a service. Similarly, a PadSpace represents Web applications, Web services, and end users' local resources as XML-tuples, and stores these XML-tuples in its core XML-tuplespace. In IntelligentPad, we represent every compound object as a pad. Therefore, we want to represent a service request also as a pad even before it is matched with a specific service, so that we can define a composite application pad using this service request pad without instantiating it to one candidate of the requested service. This service request pad, when matched with some service, works as a proxy of this service. A PadSpace represents such a service request pad as a requesting XML-tuple, and matches this XML-tuple with an appropriate service XML-tuple stored in its core XML-tuplespace. It establishes a connection between this service request pad and the matched service, and makes the service request pad to work as the proxy pad of this service. Using these mechanisms, a PadSpace provides an end user tool for the service composition of Web resources and local resources. This tool enables end users to register Web resources and local application resources into the core XML-tuplespace and to use those shared resources in combination with their own local resources by defining service compositions in the IntelligentPad architecture without writing any program codes.