System architecture : Subsystems : 2.3.3. Criterion objects (for query and subsetting)

• Introduction
• Overview of classes

Introduction

In order to allow the data centers to send back special "subsetting specifications" which would allow the user to enter various types of subsetting criteria during package-selection, ODL was created to support it.

The Web Gateway takes this ODL and converts it into objects (which, as of 1.8, are some appropriate subclass of class IU::Criterion). Such objects know how to do the following:

• Render themselves as HTML (as part of a form).

• Read the user input in from the CGI tags defined when they rendered themselves.

• Validate themselves.

• Output themselves as ODL, usually for queries or data orders.

For example, the following ODL would become an instance of IU::Criterion::InputNum:

    GROUP = SPECIALIZED_CRITERIA
      CRITERIA_NAME = "MaxGamma"
      CRITERIA_TYPE = "REAL"
      COMMENT = "Brief explanation of MaxGamma"
      CRITERIA_MIN = 0.0
      CRITERIA_MAX = 10.0
      SELECT_NUM = ONE
    END_GROUP = SPECIALIZED_CRITERIA

And this would become an instance of IU::Criterion::SelectMany:

    GROUP = SPECIALIZED_CRITERIA
      CRITERIA_NAME = "Channel"
      CRITERIA_TYPE = "STRING"
      COMMENT = ("Select one or more of the following instrument channels")
      CRITERIA_VALUE = ("19V", "19H", "36V", "36H")
      SELECT_NUM = MANY
      REQUIRED = Y
    END_GROUP = SPECIALIZED_CRITERIA

In 1.8, these objects were used to solve the similar problem of extended search criteria.

Overview of classes

Criterion classes

The following classes represent query/subsetting criteria:

  IU::Criterion             - abstract search criterion
  IU::Criterion::Geo        - a geographic region
  IU::Criterion::InputNum   - a single number/date in a query
  IU::Criterion::InputRange - a range in a query
  IU::Criterion::InputText  - a text field in a query
  IU::Criterion::SelectMany - a multiple-selection list in a query
  IU::Criterion::SelectOne  - single-selection menu in a query

Users of criteria

Collections of criteria are used by the following:

  IU::Query            - a query created through the search form
  IU::SubsetSpec       - subsetting criteria in the "choose package" page