Add information about a data set to the catalog

From OPeNDAP Documentation

Point Of Contact: James

Back: REAP Cataloging and Searching

1 Description

Give a short descriptive name for the use case to serve as a unique identifier.

AddInformation00

2 Goal

The goal briefly describes what the user intends to achieve with this use case.

The data provider would like a data set to be included in various online catalogs. By adding information those catalogs require, that becomes possible.

3 Summary

Give a summary of the use case to capture the essence of the use case (no longer than a page). It provides a quick overview and includes the goal and principal actor.

The data provider (DP) will look over the data set to get a general idea of the domain and range of the data set. They would then use a guide or some sort which will suggest which XML fragments they must write to provide support for a specific metadata documet type (e.g., what must they add so the data set will have enough information so the cataloging system can build an EML document for Kepler).

Once the DP knows what information to provide, they go about the task of writing it down in XML fragments and binding those to the data set's DAP attribute set. They will do this using the NcML-based Ancillary Information System (AIS). NcML is an XML notation which can be used to add new attributes, or replace exiting ones, using files that are external to the actual data set. NcML also provides a syntax for defining new variables for an existing data set, although we won't use that for this design. See AIS Using NcML for information on the NcML-based AIS system planned for the WCS interface to the Hyrax Data server.

Since many data sets consist of a collection of files where the content is constant in space but varies over time (or exhibits similar variations with other parameters), data providers might be faced with the task of providing the same information tens, hundreds or thousands of times over; hardly ideal. However, the NcML-based AIS system will provide two ways to address this issue:

  1. The writer may use NcML to mark some information so that it is applied to a collection of files, typically all those in a certain directory tree; and/or
  2. The writer may choose to aggregate the files to create a new logical data set where each file is an array slice or tile. Attributes are then defined for the new data set once and apply to all subsets derived from that new logical entity.

Once the XML fragments have been added to the data set, the data provider will need to see if they can be used to build a decent metadata record. Some system/software will exist to automate this process and will provide a way for the DP to determine if a working record can be built using the fragments provided.

4 Actors

List actors, people or things outside the system that either acts on the system (primary actors) or is acted on by the system (secondary actors). Primary actors are ones that invoke the use case and benefit from the result. Identify sensors, models, portals and relevant data resources. Identify the primary actor and briefly describe role.

  • The Data Provider (DP)
  • The Data set
  • The NcML-based Ancillary Information System (AIS)
  • The information regarding which XML fragments are needed to satisfy different standards/formats (The Guide)

5 Preconditions

Here we state any assumptions about the state of the system that must be met for the trigger (below) to initiate the use case. Any assumptions about other systems can also be stated here, for example, weather conditions. List all preconditions.

  • The data provider has installed/configured/tested Hyrax and is serving the data set.
  • The NcML AIS is part of that server (It will be a standard module/handler in the future, but for the time when these use cases are being used to drive the design, it will be brand new (and buggy ;-)). As a fallback, new features added to libdap 3.9.0 can be used with the existing and supported ancillary DAS to add new attributes to a data set. The ancillary DAS system/feature is no where near as powerful as the AIS, but for it can be used in a proof-of-concept fashion.
  • There exists the necessary documentation regarding what XML fragments to add for at least EML.

6 Triggers

Here we describe in detail the event or events that brings about the execution of this use case. Triggers can be external, temporal, or internal. They can be single events or when a set of conditions are met, List all triggers and relationships.

7 Basic Flow

Often referred to as the primary scenario or course of events. In the basic flow we describe the flow that would be followed if the use case where to follow its main plot from start to end. Error states or alternate states that might be highlighted are not included here. This gives any browser of the document a quick view of how the system will work. Here the flow can be documented as a list, a conversation or as a story.(as much as required)

See the Summary section.

8 Alternate Flow

Here we give any alternate flows that might occur. May include flows that involve error conditions. Or flows that fall outside of the basic flow.

Aside from various errors in creating the XML fragments...

It might be that the data provider discovers, right after adding the XML, that it's not sufficient to build the required information in the required format and that they have done all of the things described in the the Guide. In this case they have to root around and sort out what needs to be added and then add that to both the Guide. If we develop a separate software system to evaluate the completeness of the generated EML (because there are valid EML documents that won't work with the Kepler catalg search system) then that would also likely need to be updated.

9 Post Conditions

Here we give any conditions that will be true of the state of the system after the use case has been completed.

10 Activity Diagram

Here a diagram is given to show the flow of events that surrounds the use case.

11 Notes

There is always some piece of information that is required that has no other place to go. This is the place for that information.

It would be best if the system/software that builds the record(s) is also smart enough to use information already present in the variables (data) in the data set in addition to the data set's attributes. However, the initial version might do this not because it is actually fairly complicated to program since the result is often a mini rule-based system implemented in C++.

12 Resources

In order to support the capabilities described in this Use Case, a set of resources must be available and/or configured. These resources include data and services, and the systems that offer them. This section will call out examples of these resources.

  • Hyrax with the NcML AIS
  • One or more data sets
  • A DP who knows enough about the system to add the correct metadata
  • The Guide; documentation that explains what information must be present to build records fo a specific format

12.1 Other Resources

Resource Owner Description Availability Source System
(sensor name) Organization that owns/ manages resource Short description of the resource How often the resource is available Name of system which provides resource