CORES - Workshop - Exercise 3

Some questions to consider:

what criteria might you use to define/bound an Element Set?
does the principle that an Element belongs to exactly one Element Set "stand up" when applied to real examples?
what are the implications for managing Element Sets through time? Versioning?

1. Introduction

If your Application Profile contains application-specific Elements that are not part of an existing Element Set (or if they are part of an Element Set that is not described in the registry), then you will need to create a description of those Elements before creating the description of your Application Profile.

(If all the Elements "used" within your Application Profile do already appear in the registry, then you are in the fortunate position of not needing to describe an Element Set. However to familiarise yourself with this feature of the Schema Creation Tool, you may still find it useful to submit an "invented" Element Set).

The aim of the exercise is to become familiar with aspects of the data model, and the relationships between different types of resource, and with the features of the client tool.

2. Describe an Agency that regulates an Element Set

Element Sets, Encoding Schemes and Application Profiles must be associated with an Agency that is responsible for the management of that resource.

The client application works on the basis that multiple Element Sets, Encoding Schemes and Application Profiles can be described in the same Schema, but within a single Schema, all the Element Sets, Encoding Schemes and Application Profiles described are associated with a single Agency. The first step in working on a new Schema is to create a description of the Agency. The other functions on the main document window are not available until an Agency description is created.

Click the "Edit Agency" button. The Agency details form appears in a separate window. Ensure that the Agency identifier and name you supply here correspond to those you supplied when you registered with the server (or for the workshop, the Agency identifier and name provided).

You must supply the URI for the Agency. This is the only point at which the client requires you to supply a URI: default identifiers for other resources are generated using this URI as a root.

Click the "OK" button. The Agency details window closes and the main document window is updated with the name of your Agency.

This main document window shows the contents of your current Schema. The contents of the three central viewer boxes provide a representation of the RDF graph which you are building up or editing using the client. At this point it is currently empty except for the description of the Agency which you just created. All the resources described in this Schema will be associated with the Agency whose name appears in the header.

The second window is a search window. We will not use this search window in this exercise, but we shall see later that it is the main mechanism for "reusing" existing resources and describing relationships between the resources you describe and the resources described by other Schema creators.

3. Describe an Element Set

Select the Mode -- Advanced option on the menu. (The default "Simple" mode allows you to work only with Application Profiles.)

The main window changes to show three boxes, for Application Profiles, Element Sets and Encoding Schemes (instead of just the one for Application Profiles).

Click in the heading "Element Sets" to select that as the type of resource to describe, and then click "New Element Set".

A node for the Element Set (currently untitled) appears highlighted in the Element Set box, and the Element Set details form appears below. Note that the client has provided a default identifier (based on the identifier of the Agency).

Your team may decide to divide up the task of describing Elements amongst the team members. In this case, you need to ensure that you each use the same identifier for your Element Set in your separate client sessions. Set the identifier of the Element Set to a URI like http://example.org/teamN/elementSet1/ and make sure you are all using the same identifier.

Complete the description of your Element Set. N.B. This is a description of the Element Set as a whole, rather than the individual constituent Elements.

If several of your team are contributing Element descriptions, only one of you needs to describe the Element Set fully in your client session: the registry will merge the metadata you submit. However, you should all complete the Name field.

Press "OK". The node in the Element Set box is still highlighted and it now shows the name you assigned to your Element Set.

3. Describe the Elements in an Element Set

With the node for your Element Set still selected, click "Add Element".

A node for an Element (currently untitled) appears as a "child" of the Element Set node in the Element Set box, and the Element details form appears below. Again, the client has provided a default identifier. Again, for this exercise, leave that default identifier unedited.

Complete the description of your Element. N.B. The association of Encoding Schemes and Elements is described in the next exercise.

Press "OK". The Element node in the Element Set box now shows the name you assigned to your Element.

Click on the node for the Element Set so that it is highlighted again, and repeat section 3 to add a description of each Element in your Element Set

4. Save the descriptions of your Element Set (and its Elements) as a Schema

So far, you have been building up descriptions of your Element Set and its Elements in the current Schema. The nodes in the boxes in the centre of the main window show the resources you have described. The client has constructed an RDF graph in memory. This information has not so far been stored in a file. You are in the same position as if you had started editing a new document using a word processor programme, but you have not yet saved the file to disk for the first time.

Use the File -- Save menu command to save your Schema. You should be prompted for a name for your Schema document. Assign it a filename of ex3. The client appends a file suffix of .meg to these documents.

After you have saved the file, you should see that the name of the file appears in the title bar of the main document window.

Note: As with any other file editing application, it is good practice to save your work to file at regular intervals, especially during a lengthy editing session.

The file is an XML serialisation of the RDF graph representing the descriptions you have built up in the client - an "RDF Schema", if you like, though in fact the descriptions use classes and properties specific to the registry application in addition to the RDF Vocabulary Description Language (RDF Schema) classes and properties.

If you wish, you can open the ex3.meg file with a text editor and review the RDF/XML representation of your descriptions.

5. Submit the descriptions of your Element Set (and its Elements) to the Registry

You have now saved the descriptions of your Element Set and its Elements as a Schema. You now have the information stored in a file, but the descriptions have not yet been submitted to the registry.

To submit the descriptions in the current file, click the "CORES" logo in the upper right of the main document window.

A new submission window opens. Click "OK". The client should now send the descriptions to the server. Before accepting them, the server requests the userid and password of the registry administrator of this Agency. When those details are supplied, the server uploads the data, and the submission window should display a message indicating the outcome of the operation.

6. Browse the descriptions of your Element Set (and its Elements) in the Registry

Open a Web browser and go to the main menu of the registry:

http://cores.dsd.sztaki.hu/

From the main menu, go to the Agency browse page.

You should see an entry for your Agency. Follow the "details" link to open the details page for that Agency.

The Agency details page includes a list of the Element Sets owned by this Agency. That list should consist of one entry, for the Element Set you described. Follow the "details" link to open the details page for that Element Set.

The Element Set details page includes a list of the Elements of this Element Set. Follow the "details" link to open the details page for an individual Element.

7. Note on Encoding Schemes

At present, the registry permits the description of Encoding Scheme at two levels of detail

a simple description of the Encoding Scheme as a whole, including pointers to any external specifications which describe syntax or formatting rules etc i.e. the descriptions that can be submitted to the registry do not extend to descriptions of those rules (e.g. pattern matching etc);
the description of individual Values which make up a simple controlled vocabulary

Some Encoding Schemes specify that an Element has a "structured value" i.e. effectively the value is itself a second resource with its own attributes/properties. The description of Encoding Schemes here does not extend to the description of the component parts of structured values,

Similarly, the model does not cater for the description of relationships between Values within an Encoding Scheme, as for example might occur between thesaurus terms.

For both of these cases, the best solution is probably just to create a description of the Encoding Scheme as a whole.