Add attributes to a single data set

Back: AIS Using NcML

Description

Give a short descriptive name for the use case to serve as a unique identifier. Consider goal-driven use case name.

Add_Attribtues_00

Goal

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

The user adds attributes that enable 'better' or more 'complete' use of the data by a downstream data consumer (client or server-side processing module). Examples:

1. adding information so that the WCS front-end can build responses that include geo-referencing information that was not originally part of the data set
2. adding information so that EML documentation can be built for a data set
3. adding information so that a client that recognizes COARDS-compliant data sets will have the information it needs to offer those special capabilities for a data set that it otherwise could not.

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.

A person decides to add one or more attributes to a data set. They first examine the data set, maybe using DAP to look at the dataset's variables and attributes or maybe using some other tool(s), and determine what information/attributes to add. These attributes may be global attributes or they may be bound to a specific variable in the data set. They write a NcML file that describes the extra information needed and a correctly configured BES uses that *.ncml file as if it were a data set. The URL to the NcML file is effectively a new data set that contains all of the original data set's information (variables, attributes and data values) plus the information in the NcML file. The added information can be used by any downstream consumers of the data including clients and server-side processing elements.

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.

1. Primary actor: The person who writes the NcML file
2. The BES NcML handler
3. The BES
4. The data set to be modified
5. The downstream processor that will use the additional information

The person who writes the NcML file will wind up using the other actors in various ways. The most important of the other actors are the data set itself, how much information it already contains and the requirements of the intended downstream data processing element. In practice the AIS will be used to add information that can be used by several downstream data processing elements, so the NcML writer will want to have their combined requirements in mind or else will wind up repeating similar information for each downstream processor.

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.

1. The WCS Front-end is part of this Hyrax installation
2. The NcML handler has been installed and configured

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.

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)

1. The user/configurer decides to make a data set available using the WCS front-end
2. They look at the WCS documentation to see what information it needs and how that information should be represented.
3. They look at the data source and figure out what of the information needed is already there in the necessary form and what needs to be added
4. They add the extra information to a NcML file that references the original data set.
5. They store the new NcML file in a directory that the BES can use to 'serve it using the NcML handler'. This probably means any directory under the BES' DocumentRoot directory (since the BES uses regular expressions to match data sets to handlers, there's a fair amount of latitude to where the NcML file is stored).
6. They test the result.

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.

Post Conditions

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

Activity Diagram

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

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.

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.

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