Overview

The schema for the entities that actually collect, store and retrieve Assesment data parallels the hierarchical structure of the Metadata Data Model. In the antecedent "complex survey" and "questionnaire" systems, this schema was simple two-level structure:

• survey_responses which capture information about which survey was completed, by whom, when, etc
• survey_question_responses which capture the actual user data in a "long skinny table" mechanism

This suffices for one-shot surveys but doesn't support the fine granularity of user-action tracking, "save&resume" capabilities, and other requirements identified for the enhanced Assessment package. Consequently, we use a more extended hierarchy:

• Assessment Session which captures information about which Assessment, which Subject, when, etc
• Section Data which holds information about the status of each Section
• Item Data which holds the actual data extracted from the Assessment's html forms; this is the "long skinny table"

To support user modification of submitted data (of which "store&resume" is a special case), we base all these entities in the CR. In fact, we use both cr_items and cr_revisions in our schema, since for any given user's Assessment submission, there indeed is a "final" or "live" version. (In contrast, recall that for any Assessment itself, different authors may be using different versions of the Assessment. While this situation may be unusual, the fact that it must be supported means that the semantics of cr_items don't fit the Assessment itself. They do fit the semantics of a given user's Assessment "session" however.)

We distinguish here between "subjects" which are users whose information is the primary source of the Assessment's responses, and "users" which are real OpenACS users who can log into the system. Subjects may be completing the Assessment themselves or may have completed some paper form that is being transcribed by staff people who are users. We thus account for both the "real" and one or more "proxy" respondents via this mechanism. To make live not too complicated we will assume that all subjects have a user_id in OpenACS.

Note that we assume that there is only one "real" respondent. Only one student can take a test for a grade. Even if multiple clinical staff enter data about a patient, all those values still pertain to that single patient. 

Synopsis of Data-Collection Datamodel

Here's the schema for this subsystem:

Specific Entities

This section addresses the attributes the most important entities have in the data-collection data model -- principally the various design issues and choices we've made. We omit here literal SQL snippets since that's what the web interface to CVS is for. ;-)

• Assessment Sessions (as_sessions) are the top of the data-collection entity hierarchy. They provide the central definition of a given subject's performance of an Assessment. Attributes include:
  • session_id
  • cr::name - Identifier, format "$session_id-$last_mod_datetime"
    
  • assessment_id (note that this is actually a revision_id)
  • subject_id - references a Subjects entity that we don't define in this package. Should reference the users table as there is no concept of storing persons in OpenACS in general (yet)
  • staff_id - references Users if someone is doing the Assessment as a proxy for the real subject
  • target_datetime - when the subject should do the Assessment
  • creation_datetime - when the subject initiated the Assessment
  • first_mod_datetime - when the subject first sent something back in
  • last_mod_datetime - the most recent submission
  • completed_datetime - when the final submission produced a complete Assessment
  • session_status - Status of the session (and therefore of the assessment with regards to the subject)
  • ip_address - IP Address of the entry
    
  • percent_score - Current percentage of the subject achieved so far
    

• Assessment Section Data (as_section_data) tracks the state of each Section in the Assessment. Attributes include:
  • section_data_id
  • cr::name - Identifier, format "$session_id-$last_mod_datetime"
    
  • session_id
  • section_id
  • section_status

• Assessment Item Data (as_item_data) is the heart of the data collection piece. This is the "long skinny table" where all the primary data go -- everything other than "scale" data ie calculated scoring results derived from these primary responses from subjects. Attributes include:
  • item_data_id
  • session_id
  • cr::name - identifier in the format "$item_id-$subject_id"
  • subject_id
  • staff_id
  • item_id
  • choice_id_answer - references as_item_choices
  • boolean_answer
  • clob_answer
  • numeric_answer
  • integer_answer
  • varchar_answer
  • text_answer
  • timestamp_answer
  • content_answer - references cr_revisions
  • Possible Extension: item_status - Status of the answer. This might be "unanswered, delayed, answered, final". This can be put together with is_unknown_p - defaults to "f" - important to clearly distinguish an Item value that is unanswered from a value that means "We've looked for this answer and it doesn't exist" or "I don't know the answer to this". Put another way, if none of the other "value" attributes in this table have values, did the subject just decline to answer it? Or is the "answer" actually this: "there is no answer". This attribute toggles that clearly when set to "t".

• Assessment Scales will for the time being be handled by an external grading / evaluation package. Assessment will only work with percentages internally. It might be necessary to add scales into assessment as well, but we will think about this once the time arrives.

• Assessment Annotations provides a flexible way to handle a variety of ways that we need to be able to "mark up" an Assessment. Subjects may modify a response they've already made and need to provide a reason for making that change. Teachers may want to attach a reply to a student's answer to a specific Item or make a global comment about the entire Assessment. This will be achieved by using the General Comments System of OpenACS

• Signing of content allows to verify that the data submitted is actually from the person it is pretended to be from. This assumes an public key environment where the public key is stored along with the user information (e.g. with the users table) and the data stored in as_item_data is additionally stored in a signed version (signed with the secret key of the user). To verify if the data in as_item_data is actually verified the system only has to check the signed_data with the public key and see if it matches the data.