The Fedora Demo Documentation

About This Manual

• Local Server Demos - These demos can be run under any conditions. They are intended to work when the Fedora repository server is in a stand-alone condition, for example, if the repository is running without a network connection, or if the repository is behind a firewall and not set up to receive outside connections.
• Open Server Demos - These demos can only be run if the Fedora repository server is running as a network accessible server, meaning that it can make outgoing connections AND accept incoming connections. If the repository server is running behind a firewall, the firewall must be configured to allow incoming connections on the port that the repository server is running. The Open Server Demos use distributed content and services that are remote to the repository server.

http://localhost:8080/fedora/get/demo:5

Descriptions of Demos

• Simple Document Demo - This Fedora data object (objectPID is demo:18) demonstrates the simplest Fedora digital object scenario. It is the case where we aggregate content in the Fedora object, and let Fedora's default object behaviors provide access to the content. This is an example of a Fedora digital object that only has default dissemination services. In this case, there are 3 datastreams in the object, one for each format of a particular document (in this case the Fedora paper presented at ECDL2002). We can use the basic Fedora object dissemination service (also called "datastream disseminations") which are part of the basic content model shared by all objects. The basic content model is dynamically associated with every object in the repository (though it may optionally be statically associated). It has a default service definition (sDep) which provides basic operations for every object which includes the ability to list items in the object, get an item, get the dissemination index, get the Dublin Core record, and retrieve other information about the object. The results of these operations can be returned as either HTML (method names begin with "view...") or XML (method names begin with "get..."). The end result is that the object is simply a container for content and metadata. The user can view the contents and get any item from the object. While this scenario may be easy to implement and useful, it does not take advantage of Fedora's extensible service features where custom operations can be associated with an object.


• Simple Image Demo - The Fedora data object (objectPID is demo:5) demonstrates the UVA Simple Image behaviors by associating a simple dissemination with the object through its content model. There are 4 Datastreams in the object, one for each of four different image resolutions. The object is linked to one dissemination service which provides four behavior methods: getVeryHigh, getHigh, getMedium, and getThumbnail. The fulfillment of the service contract entails the Fedora HTTP Image Getter resolving the URL of the appropriate datastream for each of the UVA Simple Image behaviors. There are no transformations performed on the datastreams. This object shows how a service definition can be used to create a normalized set of methods for a particular type of object, an image object in this case, which is defined by a content model. The idea here is that the Simple Image service definition provides a standard set of dissemination services that can be used on any image object that conforms to the standard image content model. As we will see later, different variants of image objects can subscribe to the same service definition, and in some cases the datastreams will be dynamically transformed by a service to provide the appropriate image disseminations. This demo shows a simple one-to-one mapping of the datastreams in the object to the behavior methods.


• Document Transformation Demo - The Fedora data object (objectPID is demo:14) demonstrates the Document Transformation behaviors. There are 3 datastreams in the object, one XML source document, and two XSLT stylesheets. The object's content model provides one dissemination service which is associated with the "Document Transform" service definition and the Fedora Local Saxon Service (service deployment). Two services are available: getDocumentStyle1 and getDocumentStyle2. When these methods are run the repository mediates access to the Fedora Local Saxon Service to produce the appropriate transformation on the XML source in the object. The dissemination result will be one of two document styles.


• Image Collection Demo - This demo illustrates the use of the Resource Index search service to fulfill collection behaviors. For this demo to work, the Resource Index module must be enabled prior to ingesting these objects.
  
  A series of data objects (demo:SmileyBucket, demo:SmileyKeychain, etc.) subscribe to the image behaviors defined by the sDef object demo:DualResImage. Each of these image objects also use the RELS-EXT datastream to assert its membership in the demo:SmileyStuff collection. The demo:SmileyStuff collection subscribes to sDef object demo:Collection, which defines two methods: list and view. The collection object uses the demo:DualResImageCollection sDep to implement those behaviors.
  
  To see the dynamic HTML listing of collection members in action, you can view http://hostname/fedora/get/demo:SmileyStuff/demo:Collection/view
  
  This dissemination first requests the list of members of the demo:SmileyStuff collection using the local risearch service. Then it uses the local saxon service to transform the XML results into a human-readable HTML page. The query text and the stylesheet are both datastreams of the SmileyStuff collection and act as inputs to the list and view behaviors, respectively.

• Simple Image Demos - These Fedora data objects (objectPIDs are demo:6 and demo:7) demonstrate the UVA Simple Image behaviors by associating more complex disseminators with the objects. They also demonstrate how two objects with different kinds of datastreams can be made to fulfill the UVA Simple Image behavior contract. The key thing to note here is that both the demo:6 and demo:7 objects provide disseminations which subscribe to the UVA Simple Image service definition. However, they each use a different service deployment to fulfill the behavior contract. In the case of demo:7, we have an object with 4 image datastreams, one for each of four different image resolutions. In this object the UVA ImageZoomer service is used to add value to the image datastreams at runtime. When a behavior method is run, the UVA ImageZoomer service will be called upon to wrap the image in a Java applet that provides a standardized, zoomable viewer for the images. No matter which UVA Simple Image behavior is run (getVeryHigh, getHigh, getMedium, getThumbnail), the applet is provided. In the case of demo:6, we have an object with one image datastream, a wavelet-encoded MrSID file, which is passed through the UVA MrSID Service to produce results similar to those provided by the UVA ImageZoomer service. Each object's content model subscribes to the "UVA Simple Image" service definition but the services are provided by seperate service deployments such that the same four behavior methods are available (getVeryHigh, getHigh, getMedium, and getThumbnail). Another notable feature of the demo:6 object is that it shows how XML metadata can be put in the object as datastreams too. The XML metadata datastreams can be viewed via the Default Disseminator (run getItemIndex or viewItemIndex). A final important point about these demos is that the services contracted by the service deployment run remote from the repository. Both the UVA ImageZoomer service and the UVA MrSID Service run as web services at the University of Virginia. These demonstrations show how Fedora objects can leverage distributed web services, and most importantly, now the Fedora repository system handles the mediation and binding to these services in a manner that is transparent to the user.
  
  The Fedora object with objectPID demo:30 demonstrates the UVA Simple Image behaviors with yet another twist. There are 4 datastreams in the object, one for each of four different image resolutions. The object is mapped to a single dissemination service using the "UVA Simple Image" service definition and uses the Fedora HTTP Image Getter service (service deployment). As on other objects, four behavior methods are available (getVeryHigh, getHigh, getMedium, and getThumbnail). The fulfillment of the behavior contract entails the Fedora HTTP Image Getter resolving the URL of the appropriate datastream for each of the UVA Simple Image behaviors. There are no transformations performed on the datastreams. This object is almost identical to the Fedora object (objectPID of demo:5) created under the local-server-demos. The major distinction is that the datastreams for this object are of type "R" indicating that their external URLs are to be redirected by Fedora. The Fedora server typically protects the true location of external datastreams by functioning as a proxy service, thereby not exposing the physical datastream locations stored in the Fedora objects. However, there are certain situations where users may not want Fedora to proxy the location of external datastreams. For example, streaming audio and video providers may provide special optimization and performance tuning designed to function with a direct connection between a web browser and the content provider. Another example is datastreams that are protected by HTTP Basic authentication. Fedora will provide its own authentication and access policy in a future release to handle access restrictions. In the interim, the redirected datastream type can be used to access external datastreams that are protected with Basic authentication. In the Fedora object in this example, all 4 datastreams are protected on the external web server using HTTP Basic authentication which requires a username and password in order to access the datastreams. When attempting to execute the disseminations for these datastreams, you will be prompted for a username and password. The required username and password is "fedora".


• Userinput Image Demos - These Fedora data objects (objectPIDs are demo:10 and demo:11) demonstrate the UVA Userinput Image behaviors by associating more complex services with the objects. The UVA Userinput Image service definition was constructed as a demonstration to show how a service definition can allow for user input parameters at run time. In this case, the service definition has two methods (getThumbnail and getImage). The getImage method takes two user input parameters: the size of the image (e.g., small, medium1, medium2) and whether to wrap the image in a zoomable applet (yes, no). The content models of both objects share this service definition and both use the same the UVA MrSID service. Depending on what the user enters, the MrSID Service will derive the proper size of the image, and wrap it with a zoomable applet if the user requested. The UVA MrSID Service runs as web services at University of Virginia. As with the Open Server Simple Image Demos, these demonstrations show how Fedora object can leverage distributed web services.