Adding the RDH to the BES

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Point Of Contact: A Human

1 Description

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

2 Goal

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

A person who is configuring a BES daemon adds the RDH and viola, the BES can now retrieve data from an RDBMS.

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 RDH handler reads a configuration (parts of the bes.conf file?) from which it learns:

  • Which ODBC driver to load.
  • Database connection information (connection URL, database name, username, password, etc.)

It then connects to the RDMS and uses the introspection methods of ODBC to collect information about the tables and views in the target database. (This activity may happen at startup and be refreshed asynchronously, or it may be gathered each time a request for the cataolg/inventory is received))

This use case covers just how the RDH handler is added to the BES and how it uses it's configuration to establish a connection with an RDBMS.

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.

A data provider or system administrator.

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.

  1. The BES is installed and configured, except for the RDH
  2. There is an accessible RDBMS with tables and/or views containing data to be served.
  3. ODBC Data Source Definition(s) for the databases to be accessed have been created and tested on the BES host. Data Source Definitions contain the follwoing types of information:
    • The name of the Data Source Definition (which is used by processes on the host using ODBC)
    • ODBC driver string/id/thingy
    • The host name or IP address of the RDBMS system
    • The port number of the RDBMS system.
    • The user name to use for connecting to the RDBMS
    • The password associated with user name
    • The name of database in the RDBMS

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.

The trigger is the need to add this feature to the Hyrax data server. In the case of the IOOS projects, the RDH Handler will provide DAP access to in situ data stored in a RDBMS. Satisfying the requirements for that project will be the trigger. In general, the trigger will be the need to use the features of the RDH with one or more data sets.

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)

  1. User (installer/configurer) installs (builds and installs or installs a binary) of the RDH handler code
  2. The user edits the BES.conf file so that it contains the driver and connection information needed by the RDH handler to locate and connect to the RDBMS
  3. The user (re)starts the BES

Here are two relevant lines from the bes.conf file before adding the handler to the server:

BES.modules=dap,cmd,ascii,usage,www,nc,h4

We would add a ncml handler to the BES.modules line and a regular expression for it to the Typematch line like this:

BES.modules=dap,cmd,ascii,usage,www,nc,h4,drds
BES.drds.databases=name1,name2,name3

Thus any request with file that ends in .ncml (i.e., that matches teh regex .*\.ncml) as its target will be handled by the NcML handler.

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.

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.

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.


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