Computer Adaptive Testing (CAT) Service

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Executive Summary

The Computer Adaptive Testing (CAT) specification defines how to implement adaptive testing based upon assessments defined using the IMS Question and Test Interoperability® (QTI®) specification. This specification defines the data that is exchanged, and how the data is exchanged, between an Assessment delivery system and a CAT engine. The CAT engine is responsible for identifying and supplying the set of Items (the encoded questions) to be delivered in an assessment. This approach allows the use of protected algorithms (black box) with different sets of data such as psychometric data, constraints, stopping criteria, etc.

This document is the abstract description of the IMS CAT Service Model. This description uses the Unified Modelling Language (UML, to provide a diagrammatically-based solution. This description defines the set of operations that realise the data exchange and the data models that define the actual data being exchanged. The corresponding API solutions are derived from this service model through a sequence of machine-transformations [I-BAT, 06].

List of Figures

List of Tables

Table 5.1 The set of interfaces.

Table 5.2 The set of operations for the "SectionsManager" interface.

Table 5.3 The set of operations for the "SessionsManager" interface.

Table 6.1 "AssessmentResult" Class Description

Table 6.1.1 "context" Attribute Description

Table 6.1.2 "testResult" Attribute Description

Table 6.1.3 "itemResult" Attribute Description

Table 6.2 "ItemSet" Class Description

Table 6.2.1 "itemIdentifiers" Attribute Description

Table 6.3 "LUID" Class Description

Table 6.4 "NextItemSet" Class Description

Table 6.4.1 "itemIdentifiers" Attribute Description

Table 6.4.2 "stageLength" Attribute Description

Table 6.5 "Results" Class Description

Table 6.5.1 "assessmentResult" Attribute Description

Table 6.5.2 "sessionState" Attribute Description

Table 6.6 "Section" Class Description

Table 6.6.1 "qtiMetadata" Attribute Description

Table 6.6.2 "qtiUsagedata" Attribute Description

Table 6.6.3 "sectionConfiguration" Attribute Description

Table 6.7 "Session" Class Description

Table 6.7.1 "personalNeedsAndPreferences" Attribute Description

Table 6.7.2 "demographics" Attribute Description

Table 6.7.3 "priorData" Attribute Description

Table 6.8 "SessionState" Class Description

Table 6.9 "imsx_StatusInfo" Class Description

Table 6.9.1 "imsx_codeMajor" Attribute Description

Table 6.9.2 "imsx_severity" Attribute Description

Table 6.9.3 "imsx_description" Attribute Description

Table 6.9.4 "imsx_codeMinor" Attribute Description

Table 7.1.1 AssessmentResult class definitions

Table 7.1.1.1 Description of the "context" attribute for the "AssessmentResult" class

Table 7.1.1.2 Description of the "testResult" attribute for the "AssessmentResult" class

Table 7.1.1.3 Description of the "itemResult" attribute for the "AssessmentResult" class

Table 7.1.2 CandidateResponse class definitions

Table 7.1.2.1 Description of the "value" attribute for the "CandidateResponse" class

Table 7.1.3 Context class definitions

Table 7.1.3.1 Description of the "sourcedId" attribute for the "Context" class

Table 7.1.3.2 Description of the "sessionIdentifiers" attribute for the "Context" class

Table 7.1.4 CorrectResponse class definitions

Table 7.1.4.1 Description of the "interpretation" attribute for the "CorrectResponse" class

Table 7.1.4.2 Description of the "value" attribute for the "CorrectResponse" class

Table 7.1.5 ItemResult class definitions

Table 7.1.5.1 Description of the "identifier" attribute for the "ItemResult" class

Table 7.1.5.2 Description of the "sequenceIndex" attribute for the "ItemResult" class

Table 7.1.5.3 Description of the "datestamp" attribute for the "ItemResult" class

Table 7.1.5.4 Description of the "sessionStatus" attribute for the "ItemResult" class

Table 7.1.5.5 Description of the "responseVariables" attribute for the "ItemResult" class

Table 7.1.5.6 Description of the "templateVariables" attribute for the "ItemResult" class

Table 7.1.5.7 Description of the "outcomeVariables" attribute for the "ItemResult" class

Table 7.1.5.8 Description of the "candidateComment" attribute for the "ItemResult" class

Table 7.1.6 ItemSet class definitions

Table 7.1.6.1 Description of the "itemIdentifiers" attribute for the "ItemSet" class

Table 7.1.7 KeyValuePair class definitions

Table 7.1.7.1 Description of the "glossaryURI" attribute for the "KeyValuePair" class

Table 7.1.7.2 Description of the "key" attribute for the "KeyValuePair" class

Table 7.1.7.3 Description of the "value" attribute for the "KeyValuePair" class

Table 7.1.8 NextItemSet class definitions

Table 7.1.8.1 Description of the "itemIdentifiers" attribute for the "NextItemSet" class

Table 7.1.8.2 Description of the "stageLength" attribute for the "NextItemSet" class

Table 7.1.9 OutcomeVariable class definitions

Table 7.1.9.1 Description of the "identifier" attribute for the "OutcomeVariable" class

Table 7.1.9.2 Description of the "cardinality" attribute for the "OutcomeVariable" class

Table 7.1.9.3 Description of the "baseType" attribute for the "OutcomeVariable" class

Table 7.1.9.4 Description of the "view" attribute for the "OutcomeVariable" class

Table 7.1.9.5 Description of the "interpretation" attribute for the "OutcomeVariable" class

Table 7.1.9.6 Description of the "longInterpretation" attribute for the "OutcomeVariable" class

Table 7.1.9.7 Description of the "normalMaximum" attribute for the "OutcomeVariable" class

Table 7.1.9.8 Description of the "normalMinimum" attribute for the "OutcomeVariable" class

Table 7.1.9.9 Description of the "masteryValue" attribute for the "OutcomeVariable" class

Table 7.1.9.10 Description of the "value" attribute for the "OutcomeVariable" class

Table 7.1.10 PCIContext class definitions

Table 7.1.10.1 Description of the "customTypeIdentifier" attribute for the "PCIContext" class

Table 7.1.10.2 Description of the "interactionKind" attribute for the "PCIContext" class

Table 7.1.11 QTIMetadata class definitions

Table 7.1.11.1 Description of the "itemTemplate" attribute for the "QTIMetadata" class

Table 7.1.11.2 Description of the "timeDependent" attribute for the "QTIMetadata" class

Table 7.1.11.3 Description of the "composite" attribute for the "QTIMetadata" class

Table 7.1.11.4 Description of the "interactionType" attribute for the "QTIMetadata" class

Table 7.1.11.5 Description of the "portableCustomInteractionContext" attribute for the "QTIMetadata" class

Table 7.1.11.6 Description of the "feedbackType" attribute for the "QTIMetadata" class

Table 7.1.11.7 Description of the "solutionAvailable" attribute for the "QTIMetadata" class

Table 7.1.11.8 Description of the "scoringMode" attribute for the "QTIMetadata" class

Table 7.1.11.9 Description of the "toolName" attribute for the "QTIMetadata" class

Table 7.1.11.10 Description of the "toolVersion" attribute for the "QTIMetadata" class

Table 7.1.11.11 Description of the "toolVendor" attribute for the "QTIMetadata" class

Table 7.1.12 ResponseVariable class definitions

Table 7.1.12.1 Description of the "identifier" attribute for the "ResponseVariable" class

Table 7.1.12.2 Description of the "cardinality" attribute for the "ResponseVariable" class

Table 7.1.12.3 Description of the "baseType" attribute for the "ResponseVariable" class

Table 7.1.12.4 Description of the "choiceSequence" attribute for the "ResponseVariable" class

Table 7.1.12.5 Description of the "correctResponse" attribute for the "ResponseVariable" class

Table 7.1.12.6 Description of the "candidateResponse" attribute for the "ResponseVariable" class

Table 7.1.13 Results class definitions

Table 7.1.13.1 Description of the "assessmentResult" attribute for the "Results" class

Table 7.1.13.2 Description of the "sessionState" attribute for the "Results" class

Table 7.1.14 Section class definitions

Table 7.1.14.1 Description of the "qtiMetadata" attribute for the "Section" class

Table 7.1.14.2 Description of the "qtiUsagedata" attribute for the "Section" class

Table 7.1.14.3 Description of the "sectionConfiguration" attribute for the "Section" class

Table 7.1.15 Session class definitions

Table 7.1.15.1 Description of the "personalNeedsAndPreferences" attribute for the "Session" class

Table 7.1.15.2 Description of the "demographics" attribute for the "Session" class

Table 7.1.15.3 Description of the "priorData" attribute for the "Session" class

Table 7.1.16 SessionIdentifier class definitions

Table 7.1.16.1 Description of the "sourceID" attribute for the "SessionIdentifier" class

Table 7.1.16.2 Description of the "identifier" attribute for the "SessionIdentifier" class

Table 7.1.17 TemplateVariable class definitions

Table 7.1.17.1 Description of the "identifier" attribute for the "TemplateVariable" class

Table 7.1.17.2 Description of the "cardinality" attribute for the "TemplateVariable" class

Table 7.1.17.3 Description of the "baseType" attribute for the "TemplateVariable" class

Table 7.1.17.4 Description of the "value" attribute for the "TemplateVariable" class

Table 7.1.18 TestResult class definitions

Table 7.1.18.1 Description of the "identifier" attribute for the "TestResult" class

Table 7.1.18.2 Description of the "datestamp" attribute for the "TestResult" class

Table 7.1.18.3 Description of the "responseVariables" attribute for the "TestResult" class

Table 7.1.18.4 Description of the "templateVariables" attribute for the "TestResult" class

Table 7.1.18.5 Description of the "outcomeVariables" attribute for the "TestResult" class

Table 7.1.19 Value class definitions

Table 7.1.19.1 Description of the "fieldIdentifier" attribute for the "Value" class

Table 7.1.19.2 Description of the "baseType" attribute for the "Value" class

Table 7.1.19.3 Description of the "value" attribute for the "Value" class

Table 7.1.20 imsx_CodeMinor class definitions

Table 7.1.20.1 Description of the "imsx_codeMinorField" attribute for the "imsx_CodeMinor" class

Table 7.1.21 imsx_CodeMinorField class definitions

Table 7.1.21.1 Description of the "imsx_codeMinorFieldName" attribute for the "imsx_CodeMinorField" class

Table 7.1.21.2 Description of the "imsx_codeMinorFieldValue" attribute for the "imsx_CodeMinorField" class

Table 7.1.22 imsx_StatusInfo class definitions

Table 7.1.22.1 Description of the "imsx_codeMajor" attribute for the "imsx_StatusInfo" class

Table 7.1.22.2 Description of the "imsx_severity" attribute for the "imsx_StatusInfo" class

Table 7.1.22.3 Description of the "imsx_description" attribute for the "imsx_StatusInfo" class

Table 7.1.22.4 Description of the "imsx_codeMinor" attribute for the "imsx_StatusInfo" class

Table 7.2.1 IdentifierList class definitions

Table 7.2.2 LUID class definitions

Table 7.2.3 SessionState class definitions

Table 7.2.4 String256 class definitions

Table 7.2.4.1 Description of the "maxLength" attribute for the "String256" class

Table 7.3.1 BaseTypeEnum class definitions

Table 7.3.2 CardinalityEnum class definitions

Table 7.3.3 FeedbackTypeEnum class definitions

Table 7.3.4 InteractionTypeEnum class definitions

Table 7.3.5 ScoringModeEnum class definitions

Table 7.3.6 SessionStatus class definitions

Table 7.3.7 ViewEnum class definitions

Table 7.3.8 imsx_CodeMajorEnum class definitions

Table 7.3.9 imsx_CodeMinorValueEnum class definitions

Table 7.3.10 imsx_SeverityEnum class definitions

Table A3.1 The key to the descriptions of data model diagrams

Table A3.2 The key to the descriptions of the data class tables

Table A3.3 The key to the descriptions of the data attribute/characteristic tables

Table A3.4 The key to the descriptions of the enumerated vocabulary tables

Table A3.5 The key to the descriptions of the external vocabulary tables

Table A3.6 The key to the descriptions of the import class tables

1. Introduction

1.1. Scope and Context

This document is the Computer Adaptive Testing (CAT) Service Model v1.0 and as such it is used as the basis for the development of the following documents:

This information model defines the CAT Abstract Application Programming Interface (a-API). This service model is described using the Unified Modeling Language (UML) based upon the IMS Global Model Driven Specification approach and the associated modeling toolkit [I-BAT, 06]. This means that this specification is based upon the concepts of:

1.2. Conventions

All sections marked as non-normative, all authoring guidelines, diagrams (with the exception of the UML diagrams), examples, and notes in this specification are non-normative. Everything else in this specification is normative.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119]. This means that from the perspective of conformance:

The Conformance and Certification Guide for this specification may introduce greater normative constraints than those defined here for specific service or implementation categories.

The SHOULD/SHOULD NOT/RECOMMENDED statements MUST NOT be used in any document, or section of a document, that is responsible for defining the information model and/or the associated bindings and/or conformance and certification.

1.3. Structure of this Document

1.4. Nomenclature

2. The Use Cases

2.1. Use-case 1 (Initialize CAT Engine)

Table 2.1 Initialize CAT Engine
Title:	Initialize CAT Engine
Local ID:	CAT-01
Description:	A Test Driver wants to initialize a third party CAT engine for item selection.
Level	Sub-function
Actors:	Primary - Test Delivery Driver Secondary - Adaptive Engine
Stakeholder:	Administrator, Candidate
Interest:	Test Delivery Driver and CAT Engine have established communication path.
Preconditions:	Credentials/Keys have been exchanged between Test Driver and CAT Engine.
Minimal Guarantees:	The adaptive sectionTest Driver does not start section unless initialization is successful.
Success Guarantees:	The Test Driver establishes communication with CAT engine and CAT engine is ready to receive Candidate sessions.
Triggers:	Test Driver encounters "adaptive callout" within content package (see section 3.1).
Basic Flow of Events:	1. Test Driver encounters adaptive section 2. Test Driver requests section initialization from CAT Engine and provides required data a. At a minimum, the Test Driver would only provide the adaptive settings (black box). This would allow the engine to be initialized up-front; the ID of the pre-initialized section would then reside in the adaptive settings. b. In full, the test driver would provide the (byte-encoded) QTI usagedata and metadata alongside the adaptive settings; all required data would then reside within the content package. 3. CAT engine initializes and returns Section ID.
Postconditions:	Test Driver receives Section ID from CAT Engine.
Exception Handling:	1. Authentication Failure 2. Section Initialization Failure

2.2. Use-case 2 (Initialize Candidate Session)

Table 2.2 Initialize Candidate Session
Title:	Initialize Candidate Session
Local ID:	CAT-02
Description:	A Test Driver wants to initialize a session with a third-party CAT engine with Candidate information.
Level:	Sub-function
Actors:	Primary - Test Delivery Driver Secondary - Adaptive Engine
Stakeholder:	Administrator, Candidate
Preconditions:	Credentials/Keys have been exchanged between Test Driver and CAT Engine. CAT Engine has been initialized by Test Driver.
Minimal Guarantees:	The Test Driver does not start section unless a Candidate session can be established within the CAT Engine.
Success Guarantees:	The CAT engine has received relevant Candidate information and is ready to begin item selection.
Triggers:	Test Driver encounters "adaptive callout" within content package (see section 3.1).
Basic Flow of Events:	1. Test Driver requests session initialization from CAT Engine utilizing previously initialized section. 2. CAT Engine initializes and returns Session ID.
Postconditions:	Test Driver receives Session ID from CAT Engine.
Exception Handling:	1. Authentication Failure 2. Session Initialization Failure

2.3. Use-case 3 (Select Next Items)

Table 2.3 Select Next Items.
Title:	Select Next Items
Local ID:	CAT-03
Description:	A Test Driver wants to determine the next item(s) to present to Candidate.
Level	Sub-function
Actors:	Primary - Test Driver Secondary - Adaptive Engine
Stakeholder:	Administrator, Candidate
Preconditions:	Credentials/Keys have been exchanged between Test Driver and CAT Engine. CAT Engine has been initialized by Test Driver. CAT Engine has been initialized with Candidate Session.
Minimal Guarantees:	CAT Engine user session state is returned to state prior to invocation.
Success Guarantees:	0...N items are returned to present to Candidate. Zero items indicates implicit end of sectiontest.
Triggers:	Test Driver requests an item(s) to present from CAT Engine.
Basic Flow of Events:	1. Test Driver gathers Candidate response from previous item if this is not the beginning of the test. 2. Test Driver requests next items from CAT Engine. 3. Test Driver receives list of items to present to Candidate and optional stage length. 4. Test Driver present item(s) until stage length is met.
Postconditions:	Test Driver receives 0...N items to present to Candidate.
Exception Handling:	1. Authentication Failure 2. Adaptive Engine Response Failure

2.4. Use-case 4 (Terminate Candidate Session)

Table 2.4 Terminate Candidate Session
Title:	Terminate Candidate Session
Local ID:	CAT-04
Description:	A Test Delivery Driver wants to terminate a Candidate session within the CAT engine.
Level	Sub-function
Actors:	Primary - Test Delivery Driver Secondary - Adaptive Engine
Stakeholder:	Administrator, Candidate
Preconditions:	Credentials/Keys have been exchanged between Test Driver and CAT Engine. A Candidate session has been established.
Minimal Guarantees:	CAT Engine Candidate session state is returned to state prior to invocation.
Success Guarantees:	CAT Engine terminates Candidate session and cleans up resources related to it.
Triggers:	No more items are available to present.
Basic Flow of Events:	1. Test Driver requests session termination from CAT Engine utilizing previously initialized Candidate session. 2. CAT Engine cleans up all resources related to Candidate session.
Postconditions:	Test Driver has completed AssessmentSection and is ready to deliver next AssessmentSection.
Exception Handling:	1. Authentication Failure 2. Adaptive Engine Response Failure

3. The Conceptual Model

The CAT service defines how adaptive engines can be used with other delivery engines in presenting adaptive tests to candidates. It does not specify the adative algorithms. Instead the internal functionality of the adaptive engine is treated as a 'black box'. A schematic representation of the service provided by the CAT specification is shown in Figure 3.1.

4. Service Architecture and Specification Model

4.1. An Abstract Representation

It is important to remember that this document contains a description of the underlying information model in terms of the abstract Application Programming Interface (API). The manner in which this abstract representation is visualized is not intended to dictate the implementation form of the Service. The breakdown of the service into its interface classes is a convenient way to document the set of behaviors. The objective for producing these interfaces is to identify and define the messages that are exchanged between the end-systems to realize the system behaviors required of the service.

The internal organization of an implementation of the full abstract API is beyond the scope of this specification. The only constraint is that the external behavior of the abstract API complies with this specification. This means that a .NET, J2EE, etc. physical implementation of this abstract API does not have to represent the functionality using the same breakdown of operations/methods. This physical implementation is not subject to the conformance specification.

It is important to note that the UML representation of the interfaces is used to help develop and document the Information Model and various Bindings. It is not a requirement for a system to implement this interface as defined i.e. to use the same parameters, etc. Conformance against this specification will be confirmed by inspecting the appropriate binding of the information model and ensuring that the relevant information is present and that different sequences of activity result in the predicted and mandated behavior. It is essential that the behaviors described by each of the operations are fully supported and that the behaviors described by different sequences are also maintained.

4.2. Service Architecture and Specification Model

The basic architectural model for the CAT Service specification is shown in Figure 4.1. In this architecture the scope of the IMS CAT Service specification is shown as the dotted line. The scope of the interoperability is the data and behavioral models of the objects being exchanged.

4.3. Service Objects

The set of service collection objects that are exchanged between end-systems are:

4.4. The CAT Service Choreography

The CAT Service consists of a set of synchronous message exchanges, i.e. the consumer is blocked until the response from the provider is received. This means that a consumer can only have one outstanding request with a CAT Engine. A typical sequence of actions is shown in Figure 4.2.

5. The Behavior Model

5.1 Service Definition

Table 5.1 The set of interfaces.
Interface	Description
SectionsManager	The set of service operations that manage access to the adaptive Sections being handled by the CAT Engine.
SessionsManager	The set of service operations that manage access to the adaptive Sessions being handled by the CAT Engine.

5.2 SectionsManager Interface Description

Table 5.2 The set of operations for the "SectionsManager" interface.
Operation	Description
createSection	This is a request to the CAT Engine to create a new adaptive Section. The CAT Engine is responsible for assigning the unique identifier to be used for this Section in other exchanges. This request is NOT idempotent.
getSection	This request returns the parameters which were used by the CAT engine to create the adaptive section, and the list of the items in the adaptive section's item pool, as configured by the CAT engine. It is recommended that assessment platforms and/or delivery engines use this request to verify that the item pool, as configured by the CAT engine, corresponds exactly to the list of items in the QTI source for the adaptive section. It is also recommended that test administrators verify that each item in the item pool is accessible and deliverable before commencing delivery of candidate sessions. The Get Section request may be used for this, and may be made at any time after a successful Create Section request, as many times as required.
endSection	This request ends all candidate sessions for the section which have not already ended, and ends the section. The sectionIdentifier, sessionIdentifiers, and sessionStates returned from previous requests related to the section become invalid. The delivery engine should not make any further requests related to the section or any session for the section. For a REST-based binding this request uses the DELETE HTTP method because of REST conventions, but the CAT engine is not required to physically delete any session or section data. This request should not be repeated once it has succeeded.

5.2.1 "createSection" Operation

5.2.2 "getSection" Operation

5.2.3 "endSection" Operation

5.3 SessionsManager Interface Description

Table 5.3 The set of operations for the "SessionsManager" interface.
Operation	Description
createSession	This request initializes a candidate session for the adaptive section. The request optionally provides the CAT engine with information related to the candidate. The CAT engine returns the initial stage (list of items) to be presented to the candidate. This request may be made multiple times after a successful Create Section request, once per candidate, when each candidate enters the adaptive section on the test. This request is NOT idempotent.
endSession	This request ends the candidate session. The sessionIdentifier, and the sessionState returned from any previous request in the session, become invalid. The delivery engine should not make any further requests related to the session. For a REST-based binding this request uses the DELETE HTTP method because of REST conventions; but it is not required that CAT engines physically delete data or resources associated with the session. If the identified session cannot be found then the 'unknownobject' status code must be reported.
submitResults	This request sends the results from the current item stage in a candidate session to the CAT engine. The CAT engine returns its computed outcome variable values for the current stage and the test as a whole. It also returns the next item stage to be presented to the candidate. Instead of the next item stage, it may also return an indication that the adaptive section has ended, by returning an empty list for nextItems. If the identified Section/Session cannot be found then the 'unknownobject' status code must be reported.

5.3.1 "createSession" Operation

5.3.2 "endSession" Operation

5.3.3 "submitResults" Operation

6. The Interface Model

6.1 AssessmentResult Class Description

Table 6.1 Description of the "AssessmentResult" class.
Descriptor	Definition
Class Name	AssessmentResult
Class Type	Container [ Sequence ]
Parents	Service parameter data-type used in the following operations: submitResults
Characteristics	There are no characteristics.
Children	The set of children attributes are: context testResult itemResult
Description	An Assessment Result is used to report the results of a candidate's interaction with a test and/or one or more items attempted. Information about the test is optional, in some systems it may be possible to interact with items that are not organized into a test at all. For example, items that are organized with learning resources and presented individually in a formative context.

6.1.1 "context" Attribute Description

Table 6.1.1 Description of the "context" attribute for the "AssessmentResult" class.
Descriptor	Definition
Attribute Name	context
Data Type	Context
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0..1]
Description	Contains contextual information for the associated testResult and itemResults.

6.1.2 "testResult" Attribute Description

Table 6.1.2 Description of the "testResult" attribute for the "AssessmentResult" class.
Descriptor	Definition
Attribute Name	testResult
Data Type	TestResult
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0..1]
Description	A summary report for a test is represented by an assessment result containing a testResult but no itemResults.

6.1.3 "itemResult" Attribute Description

Table 6.1.3 Description of the "itemResult" attribute for the "AssessmentResult" class.
Descriptor	Definition
Attribute Name	itemResult
Data Type	ItemResult
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	When a test result is given the following item results must relate only to items that were selected for presentation as part of the corresponding test session. Furthermore, all items selected for presentation should be reported with a corresponding itemResult.

6.2 ItemSet Class Description

Table 6.2 Description of the "ItemSet" class.
Descriptor	Definition
Class Name	ItemSet
Class Type	Container [ Unordered ]
Parents	Service parameter data-type used in the following operations: getSection
Characteristics	There are no characteristics.
Children	The set of children attributes are: itemIdentifiers
Description	A set of Item identfiers.

6.2.1 "itemIdentifiers" Attribute Description

Table 6.2.1 Description of the "itemIdentifiers" attribute for the "ItemSet" class.
Descriptor	Definition
Attribute Name	itemIdentifiers
Data Type	LUID
Value Space	Container [ DerivedType ]
Scope	Local ("-")
Multiplicity	[1.. unbounded]
Description	The Identifiers for the set of Items. These should be the GUIDs that have been assigned to AssessmentItems when defined using IMS QTI.

6.3 LUID Class Description

Table 6.3 Description of the "LUID" class.
Descriptor	Definition
Class Name	LUID
Class Type	Container [ DerivedType ]
Parents	Service parameter data-type used in the following operations: createSection getSection endSection createSession endSession submitResults
Characteristics	There are no characteristics.
Children	There are no children.
Description	The data-type for establishing a Locally Unique Identifier (LUID) - this must be unique for the set of Section and Session interactions between the consumer and the CAT Engine. The form of the LUID is unrestricted.

6.4 NextItemSet Class Description

Table 6.4 Description of the "NextItemSet" class.
Descriptor	Definition
Class Name	NextItemSet
Class Type	Container [ Unordered ]
Parents	Service parameter data-type used in the following operations: createSession submitResults
Characteristics	There are no characteristics.
Children	The set of children attributes are: itemIdentifiers stageLength
Description	The container for the information about the set of next Items that should be presented to the examinee.

6.4.1 "itemIdentifiers" Attribute Description

Table 6.4.1 Description of the "itemIdentifiers" attribute for the "NextItemSet" class.
Descriptor	Definition
Attribute Name	itemIdentifiers
Data Type	LUID
Value Space	Container [ DerivedType ]
Scope	Local ("-")
Multiplicity	[1.. unbounded]
Description	The Identifiers for the set of Items that should be presented next. These should be the GUIDs that have been assigned to AssessmentItems when defined using IMS QTI.

6.4.2 "stageLength" Attribute Description

Table 6.4.2 Description of the "stageLength" attribute for the "NextItemSet" class.
Descriptor	Definition
Attribute Name	stageLength
Data Type	NonNegativeInteger (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	The (minimum) number of items the CAT Engine can present before requesting next items

6.5 Results Class Description

Table 6.5 Description of the "Results" class.
Descriptor	Definition
Class Name	Results
Class Type	Container [ Unordered ]
Parents	Service parameter data-type used in the following operations: submitResults
Characteristics	There are no characteristics.
Children	The set of children attributes are: assessmentResult sessionState
Description	This is the container for the results that have been accrued by the examinee. These are passed to the CAT Engine to support the selection of the next set of Items.

6.5.1 "assessmentResult" Attribute Description

Table 6.5.1 Description of the "assessmentResult" attribute for the "Results" class.
Descriptor	Definition
Attribute Name	assessmentResult
Data Type	AssessmentResult
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[1]
Description	The set of actual results achieved by the examinee (this is equivalent to the IMS QTI 2.2 Results Reporting data model [QTI, 20b]).

6.5.2 "sessionState" Attribute Description

Table 6.5.2 Description of the "sessionState" attribute for the "Results" class.
Descriptor	Definition
Attribute Name	sessionState
Data Type	SessionState
Value Space	Container [ DerivedType ]
Scope	Local ("-")
Multiplicity	[0..1]
Description	The session state information. This is the data that was supplied by the CAT Engine when the session was created or the next set of Items was requested.

6.6 Section Class Description

Table 6.6 Description of the "Section" class.
Descriptor	Definition
Class Name	Section
Class Type	Container [ Unordered ]
Parents	Service parameter data-type used in the following operations: createSection getSection
Characteristics	There are no characteristics.
Children	The set of children attributes are: qtiMetadata qtiUsagedata sectionConfiguration
Description	The container for the definition of the Section that is to be created in the CAT Engine. A Section is aligned to a QTI AssessmentSection [QTI, 20a].

6.6.1 "qtiMetadata" Attribute Description

Table 6.6.1 Description of the "qtiMetadata" attribute for the "Section" class.
Descriptor	Definition
Attribute Name	qtiMetadata
Data Type	QTIMetadata
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0..1]
Description	This is the container for the QTI metadata. Part of this metadata uses the IMS QTI 3.0 Metadata model [QTI, 20d].

6.6.2 "qtiUsagedata" Attribute Description

Table 6.6.2 Description of the "qtiUsagedata" attribute for the "Section" class.
Descriptor	Definition
Attribute Name	qtiUsagedata
Data Type	String (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	This is the Base64 encoded XML conforming to IMS QTI 3.0 Usage Date data model [QTI, 20c].

6.6.3 "sectionConfiguration" Attribute Description

Table 6.6.3 Description of the "sectionConfiguration" attribute for the "Section" class.
Descriptor	Definition
Attribute Name	sectionConfiguration
Data Type	String (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[1]
Description	This is the Base64 encoded data containing section configuration, aligned with adaptive engine (black box). This format will be proprietary to each adaptive CAT Engine.

6.7 Session Class Description

Table 6.7 Description of the "Session" class.
Descriptor	Definition
Class Name	Session
Class Type	Container [ Unordered ]
Parents	Service parameter data-type used in the following operations: createSession
Characteristics	There are no characteristics.
Children	The set of children attributes are: personalNeedsAndPreferences demographics priorData
Description	This is the container for the session configuration data that must be supplied to the CAT Engine when the session is to be created.

6.7.1 "personalNeedsAndPreferences" Attribute Description

Table 6.7.1 Description of the "personalNeedsAndPreferences" attribute for the "Session" class.
Descriptor	Definition
Attribute Name	personalNeedsAndPreferences
Data Type	NormalizedString (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	This is the Base64 encoded XML data for the Personal Needs and Preferences (PNP) for the examinee. This data conforms to the XML as defined in the IMS Access for All Personal Needs and Preferences (AfAPNP) 3.0 XML Binding specification [AFAPNP, 20].

6.7.2 "demographics" Attribute Description

Table 6.7.2 Description of the "demographics" attribute for the "Session" class.
Descriptor	Definition
Attribute Name	demographics
Data Type	NormalizedString (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	The Base64 encoding of the JSON data for the Demographics information for the examinee. This data conforms to the JSON as defined in the IMS OneRoster 1.1 specification [OR, 17].

6.7.3 "priorData" Attribute Description

Table 6.7.3 Description of the "priorData" attribute for the "Session" class.
Descriptor	Definition
Attribute Name	priorData
Data Type	KeyValuePair
Value Space	Container [ Unordered ]
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	This is proprietary data that is supplied to the CAT Engine as a key/value pairs.

6.8 SessionState Class Description

Table 6.8 Description of the "SessionState" class.
Descriptor	Definition
Class Name	SessionState
Class Type	Container [ DerivedType ]
Parents	Service parameter data-type used in the following operations: createSession submitResults
Characteristics	There are no characteristics.
Children	There are no children.
Description	This is the container for the Base64 encoded session data, aligned with the adaptive CAT Engine (black box). In general this will be a proprietary format.

6.9 imsx_StatusInfo Class Description

Table 6.9 Description of the "imsx_StatusInfo" class.
Descriptor	Definition
Class Name	imsx_StatusInfo
Class Type	Container [ Sequence ]
Parents	Service parameter data-type used in the following operations: createSection getSection endSection createSession endSession submitResults
Characteristics	There are no characteristics.
Children	The set of children attributes are: imsx_codeMajor imsx_severity imsx_description imsx_codeMinor
Description	This is the container for the status code and associated information returned within the HTTP messages received from the Service Provider.

6.9.1 "imsx_codeMajor" Attribute Description

Table 6.9.1 Description of the "imsx_codeMajor" attribute for the "imsx_StatusInfo" class.
Descriptor	Definition
Attribute Name	imsx_codeMajor
Data Type	imsx_CodeMajorEnum
Value Space	Enumerated value set of: { success \| processing \| failure \| unsupported }
Scope	Local ("-")
Multiplicity	[1]
Description	The code major value (from the corresponding enumerated vocabulary).

6.9.2 "imsx_severity" Attribute Description

Table 6.9.2 Description of the "imsx_severity" attribute for the "imsx_StatusInfo" class.
Descriptor	Definition
Attribute Name	imsx_severity
Data Type	imsx_SeverityEnum
Value Space	Enumerated value set of: { status \| warning \| error }
Scope	Local ("-")
Multiplicity	[1]
Description	The severity value (from the corresponding enumerated vocabulary).

6.9.3 "imsx_description" Attribute Description

Table 6.9.3 Description of the "imsx_description" attribute for the "imsx_StatusInfo" class.
Descriptor	Definition
Attribute Name	imsx_description
Data Type	String (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	A human readable description supplied by the entity creating the status code information.

6.9.4 "imsx_codeMinor" Attribute Description

Table 6.9.4 Description of the "imsx_codeMinor" attribute for the "imsx_StatusInfo" class.
Descriptor	Definition
Attribute Name	imsx_codeMinor
Data Type	imsx_CodeMinor
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0..1]
Description	The set of reported code minor status codes.

7. Data Model

7.1. Data Class Descriptions

All of the data classes used within this Information Model are described in this Section. The syntax and semantics for this representation is described in Appendix A3.2.

7.1.1 AssessmentResult Class Description

Table 7.1.1 Description of the "AssessmentResult" class.
Descriptor	Definition
Class Name	AssessmentResult
Class Type	Container [ Sequence ]
Parents	The set of parent classes are: Results
Derived Classes	There are no derived classes.
Super Classes	This class is not derived from another class.
Characteristics	There are no characteristics.
Children	The set of children attributes are: context testResult itemResult
Description	An Assessment Result is used to report the results of a candidate's interaction with a test and/or one or more items attempted. Information about the test is optional, in some systems it may be possible to interact with items that are not organized into a test at all. For example, items that are organized with learning resources and presented individually in a formative context.

7.1.1.1 "context" Attribute Description

Table 7.1.1.1 Description of the "context" attribute for the "AssessmentResult" class.
Descriptor	Definition
Attribute Name	context
Data Type	Context
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0..1]
Description	Contains contextual information for the associated testResult and itemResults.

7.1.1.2 "testResult" Attribute Description

Table 7.1.1.2 Description of the "testResult" attribute for the "AssessmentResult" class.
Descriptor	Definition
Attribute Name	testResult
Data Type	TestResult
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0..1]
Description	A summary report for a test is represented by an assessment result containing a testResult but no itemResults.

7.1.1.3 "itemResult" Attribute Description

Table 7.1.1.3 Description of the "itemResult" attribute for the "AssessmentResult" class.
Descriptor	Definition
Attribute Name	itemResult
Data Type	ItemResult
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	When a test result is given the following item results must relate only to items that were selected for presentation as part of the corresponding test session. Furthermore, all items selected for presentation should be reported with a corresponding itemResult.

7.1.2 CandidateResponse Class Description

Table 7.1.2 Description of the "CandidateResponse" class.
Descriptor	Definition
Class Name	CandidateResponse
Class Type	Container [ Sequence ]
Parents	The set of parent classes are: ResponseVariable
Derived Classes	There are no derived classes.
Super Classes	This class is not derived from another class.
Characteristics	There are no characteristics.
Children	The set of children attributes are: value
Description	The response given by the candidate.

7.1.2.1 "value" Attribute Description

Table 7.1.2.1 Description of the "value" attribute for the "CandidateResponse" class.
Descriptor	Definition
Attribute Name	value
Data Type	Value
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	The value(s) of the response variable. A NULL value, resulting from no response, is indicated by the absence of any value. The order of the values is significant only if the response was declared with ordered cardinality.

7.1.3 Context Class Description

Table 7.1.3 Description of the "Context" class.
Descriptor	Definition
Class Name	Context
Class Type	Container [ Sequence ]
Parents	The set of parent classes are: AssessmentResult
Derived Classes	There are no derived classes.
Super Classes	This class is not derived from another class.
Characteristics	There are no characteristics.
Children	The set of children attributes are: sourcedId sessionIdentifiers
Description	This is the context for the 'assessmentResult'. It provides the corresponding set of identifiers.

7.1.3.1 "sourcedId" Attribute Description

7.1.3.2 "sessionIdentifiers" Attribute Description

7.1.4 CorrectResponse Class Description

7.1.4.1 "interpretation" Attribute Description

7.1.4.2 "value" Attribute Description

7.1.5 ItemResult Class Description

7.1.5.1 "identifier" Attribute Description

7.1.5.2 "sequenceIndex" Attribute Description

7.1.5.3 "datestamp" Attribute Description

7.1.5.4 "sessionStatus" Attribute Description

7.1.5.5 "responseVariables" Attribute Description

7.1.5.6 "templateVariables" Attribute Description

7.1.5.7 "outcomeVariables" Attribute Description

7.1.5.8 "candidateComment" Attribute Description

7.1.6 ItemSet Class Description

7.1.6.1 "itemIdentifiers" Attribute Description

7.1.7 KeyValuePair Class Description

7.1.7.1 "glossaryURI" Attribute Description

7.1.7.2 "key" Attribute Description

7.1.7.3 "value" Attribute Description

7.1.8 NextItemSet Class Description

7.1.8.1 "itemIdentifiers" Attribute Description

7.1.8.2 "stageLength" Attribute Description

7.1.9 OutcomeVariable Class Description

7.1.9.1 "identifier" Attribute Description

7.1.9.2 "cardinality" Attribute Description

7.1.9.3 "baseType" Attribute Description

7.1.9.4 "view" Attribute Description

7.1.9.5 "interpretation" Attribute Description

7.1.9.6 "longInterpretation" Attribute Description

7.1.9.7 "normalMaximum" Attribute Description

7.1.9.8 "normalMinimum" Attribute Description

7.1.9.9 "masteryValue" Attribute Description

7.1.9.10 "value" Attribute Description

7.1.10 PCIContext Class Description

7.1.10.1 "customTypeIdentifier" Attribute Description

7.1.10.2 "interactionKind" Attribute Description

7.1.11 QTIMetadata Class Description

7.1.11.1 "itemTemplate" Attribute Description

7.1.11.2 "timeDependent" Attribute Description

7.1.11.3 "composite" Attribute Description

7.1.11.4 "interactionType" Attribute Description

7.1.11.5 "portableCustomInteractionContext" Attribute Description

7.1.11.6 "feedbackType" Attribute Description

7.1.11.7 "solutionAvailable" Attribute Description

7.1.11.8 "scoringMode" Attribute Description

7.1.11.9 "toolName" Attribute Description

7.1.11.10 "toolVersion" Attribute Description

7.1.11.11 "toolVendor" Attribute Description

7.1.12 ResponseVariable Class Description

7.1.12.1 "identifier" Attribute Description

7.1.12.2 "cardinality" Attribute Description

7.1.12.3 "baseType" Attribute Description

7.1.12.4 "choiceSequence" Attribute Description

7.1.12.5 "correctResponse" Attribute Description

7.1.12.6 "candidateResponse" Attribute Description

7.1.13 Results Class Description

7.1.13.1 "assessmentResult" Attribute Description

7.1.13.2 "sessionState" Attribute Description

7.1.14 Section Class Description

7.1.14.1 "qtiMetadata" Attribute Description

7.1.14.2 "qtiUsagedata" Attribute Description

7.1.14.3 "sectionConfiguration" Attribute Description

7.1.15 Session Class Description

7.1.15.1 "personalNeedsAndPreferences" Attribute Description

7.1.15.2 "demographics" Attribute Description

7.1.15.3 "priorData" Attribute Description

7.1.16 SessionIdentifier Class Description

7.1.16.1 "sourceID" Attribute Description

7.1.16.2 "identifier" Attribute Description

7.1.17 TemplateVariable Class Description

7.1.17.1 "identifier" Attribute Description

7.1.17.2 "cardinality" Attribute Description

7.1.17.3 "baseType" Attribute Description

7.1.17.4 "value" Attribute Description

7.1.18 TestResult Class Description

7.1.18.1 "identifier" Attribute Description

7.1.18.2 "datestamp" Attribute Description

7.1.18.3 "responseVariables" Attribute Description

7.1.18.4 "templateVariables" Attribute Description

7.1.18.5 "outcomeVariables" Attribute Description

7.1.19 Value Class Description

7.1.19.1 "fieldIdentifier" Attribute Description

7.1.19.2 "baseType" Attribute Description

7.1.19.3 "value" Attribute Description

7.1.20 imsx_CodeMinor Class Description

7.1.20.1 "imsx_codeMinorField" Attribute Description

7.1.21 imsx_CodeMinorField Class Description

7.1.21.1 "imsx_codeMinorFieldName" Attribute Description

7.1.21.2 "imsx_codeMinorFieldValue" Attribute Description

7.1.22 imsx_StatusInfo Class Description

7.1.22.1 "imsx_codeMajor" Attribute Description

7.1.22.2 "imsx_severity" Attribute Description

7.1.22.3 "imsx_description" Attribute Description

7.1.22.4 "imsx_codeMinor" Attribute Description

7.2. Derived Class Descriptions

All of the derived data classes used within this Information Model are described in this Section. The syntax and semantics for this representation is described in Appendix A3.2.

7.2.1 IdentifierList Class Description

7.2.2 LUID Class Description

7.2.3 SessionState Class Description

7.2.4 String256 Class Description

7.2.4.1 "maxLength" Attribute Description

7.3. Enumerated Vocabulary Descriptions

All of the enumerated vocabularies used within this Information Model are described in this Section. The syntax and semantics for this representation is described in Appendix A3.4.

7.3.1 BaseTypeEnum Vocabulary Description

7.3.2 CardinalityEnum Vocabulary Description

7.3.3 FeedbackTypeEnum Vocabulary Description

7.3.4 InteractionTypeEnum Vocabulary Description

7.3.5 ScoringModeEnum Vocabulary Description

7.3.6 SessionStatus Vocabulary Description

7.3.7 ViewEnum Vocabulary Description

7.3.8 imsx_CodeMajorEnum Vocabulary Description

7.3.9 imsx_CodeMinorValueEnum Vocabulary Description

7.3.10 imsx_SeverityEnum Vocabulary Description

8. Link Data Definitions

9. Extending and Profiling the Service

9.1. Extending the Service

It is NOT permitted to change the behavior of the current set of operations. Such changes MUST be supported by the creation of new operations.

9.1.1. Proprietary Operations

The definition of new operations should follow the same format as adopted herein. The new operations should be defined using a new interface type. Every operation must result in the return of a status code that describes the final state of the request on the target end system.

An example of creating such an extension is given in the accompanying Best Practices document [CAT, 20b].

9.1.2. Proprietary Data Elements

Extensions to the data model are only permitted where the IMSExtension class is available. Currently, data extensions are NOT permitted.

9.2. Profiling the Service

Valid Profiles must be restrictive i.e. optional features can be removed or constraints increased but new features must not be added. A Profile of this service is made by annotating the UML supplied with the documentation for the specification.

It is strongly recommended that a profile of this specification is undertaken either by, or with the close support, of IMS Global. However, no matter who is responsible for creating the profile artifacts (documents, XSDs, etc.), it is strongly recommended that the IMS specification tools are used. This will ensure that the artifacts are consistent with the base specifications and that useful support documentation is automatically produced e.g. creation of a document that summarizes the differences between the base specification and the profile. Organizations wishing to produce a profile of this specification should contact Lisa Mattson (IMS Global Chief Operations Officer) at: lmattson@imsglobal.org.

References

Appendix A Modeling Concepts and Terms

A1 Behavior Descriptions Explanations

A1.1 Service Model Diagrams

A1.2 Operation Descriptions

A2 Interface Descriptions Explanations

A2.1 Parameter Model Diagrams

A2.2 Class Descriptions

A2.3 Attribute Descriptions

A3 Data Model Descriptions Explanations

A3.1 Data Model Diagrams

A3.2 Class Descriptions

A3.3 Attribute and Characteristic Descriptions

Table A3.3 provides the key to the descriptions of the data attributes/characteristics for the data classes.

A3.4 Enumerated Vocabulary Descriptions

Table A3.4 provides the key to the descriptions of the enumerated vocabulary classes. These are vocabularies that will be contained within the binding form itself. They are contained within a class that has a stereotype of either « Enumeration » or « EnumeratedList ».

A3.5 External Vocabulary Descriptions

Table A3.5 provides the key to the descriptions of the external vocabulary classes. These are vocabularies that will be contained in some independent format e.g. using the IMS VDEX [VDEX, 04].

A3.6 Import Class Descriptions

A3.7 Link Data Descriptions

Appendix B Service Status Codes

B1 Definition of the Status Codes

The interpretation of the "CodeMajor/Severity" behavior matrix is summarized in Table B1.1.

B1.1 Definition of the "CodeMajor" Values

B1.2 Definition of the "Severity" Values

B1.3 Definition of the "CodeMinor" Values

About this Document

List of Contributors

Revision History

IMS Global Learning Consortium, Inc. ("IMS Global") is publishing the information contained in this document ("Specification") for purposes of scientific, experimental, and scholarly collaboration only.

IMS Global makes no warranty or representation regarding the accuracy or completeness of the Specification.

The Specification is at all times subject to change and revision without notice.

It is your sole responsibility to evaluate the usefulness, accuracy, and completeness of the Specification as it relates to you.

Date Issued:	2021-02-01
Latest version:	http://www.imsglobal.org/cat/latest/

Name:	createSection ()
Return Function Parameter:	statusInfo : imsx_StatusInfo - the status information report for the request. This report has end-to-end significance and must map between the messaging technology approach and the business transaction API.
Supplied (in) Parameters:	section : Section - the data for the configuration of the new adaptive Section.
Returned (out) Parameters:	sectionIdentifier : LUID - the LUID that has been assigned by the CAT Engine to the new Section (this has no significance in the context of a QTI Section definition).
Behavior:	This is a request to the CAT Engine to create a new adaptive Section. The CAT Engine is responsible for assigning the unique identifier to be used for this Section in other exchanges. This request is NOT idempotent.

Name:	getSection ()
Return Function Parameter:	imsx_StatusInfo : imsx_StatusInfo - the status information report for the request. This report has end-to-end significance and must map between the messaging technology approach and the business transaction API.
Supplied (in) Parameters:	sectionIdentifier : LUID - the LUID that identifies the Section for which the data on the CAT Engine is to be obtained.
Returned (out) Parameters:	items : ItemSet - the list of Items (the identifiers) in the Section's item pool. section : Section - the set of parameters that were used to create the adaptive Section.
Behavior:	This request returns the parameters which were used by the CAT engine to create the adaptive section, and the list of the items in the adaptive section's item pool, as configured by the CAT engine. It is recommended that assessment platforms and/or delivery engines use this request to verify that the item pool, as configured by the CAT engine, corresponds exactly to the list of items in the QTI source for the adaptive section. It is also recommended that test administrators verify that each item in the item pool is accessible and deliverable before commencing delivery of candidate sessions. The Get Section request may be used for this, and may be made at any time after a successful Create Section request, as many times as required.

Name:	endSection ()
Return Function Parameter:	statusInfo : imsx_StatusInfo - the status information report for the request. This report has end-to-end significance and must map between the messaging technology approach and the business transaction API.
Supplied (in) Parameters:	sectionIdentifier : LUID - the LUID that identifies the Section to be deleted on the CAT Engine.
Returned (out) Parameters:	None.
Behavior:	This request ends all candidate sessions for the section which have not already ended, and ends the section. The sectionIdentifier, sessionIdentifiers, and sessionStates returned from previous requests related to the section become invalid. The delivery engine should not make any further requests related to the section or any session for the section. For a REST-based binding this request uses the DELETE HTTP method because of REST conventions, but the CAT engine is not required to physically delete any session or section data. This request should not be repeated once it has succeeded.

Name:	createSession ()
Return Function Parameter:	imsx_StatusInfo : imsx_StatusInfo - the status information report for the request. This report has end-to-end significance and must map between the messaging technology approach and the business transaction API.
Supplied (in) Parameters:	sectionIdentifier : LUID - the LUID that identifies the Section in the CAT Engine to which this new Session is to be assigned. session : Session - the Session configuration data including the information about the examinee.
Returned (out) Parameters:	sessionIdentifier : LUID - the LUID that has been assigned by the CAT Engine to the new Session. nextItems : NextItemSet - the initial sequence of Items to administer to this examinee. sessionState : SessionState - the session state to send back on subsequent calls within this session.
Behavior:	This request initializes a candidate session for the adaptive section. The request optionally provides the CAT engine with information related to the candidate. The CAT engine returns the initial stage (list of items) to be presented to the candidate. This request may be made multiple times after a successful Create Section request, once per candidate, when each candidate enters the adaptive section on the test. This request is NOT idempotent.

2. The Use Cases	The set of core use cases supported by this specification. This includes the exchange of QTI based items or tests intended to be adaptive;
3. The Conceptual Model	The conceptual model underlying this computer adaptive testing service. This includes definition of the end-systems that are exchanging this data;
4. Service Architecture and Specification Model	An overview of the service including the key use cases and the underlying service architecture and end-system service objects.
5. The Behavior Model	The definition of the operations of the service. This focuses on the description of the behaviors supported by the service. The behaviors are grouped as interfaces;
6. The Interface Model	The definition of the data models exchanged between the service End Systems. These are the parameters exchanged across the interoperability interface. These are an abbreviated description with the full set of details in the corresponding data class description;
7. Data Model	The definition of the data classes for the full data exchange. This addresses the data classes used to supplement the interface parameters. The descriptions are grouped according to their type e.g. data, enumeration, derived, etc;
8. Link Data Definitions	The set of descriptions for the link data definitions that are used to establish the intra- and inter- specification relationships;
9. Extending and Profiling the Service	An explanation of how the service can be extended, using the permitted points of extension, and/or profiled. Profiling is the process by which the specification is tailored to a specific set of market/domain requirements;
References	The set of cited documents, normative and informative, that are used to support the technical details in this document;
Appendix A Modeling Concepts and Terms	An overview of the model driven approach, the concepts and the terms used by IMS to create the service model representations (based upon a profile of UML), the corresponding set of bindings and the accompanying documentation (including this information model);
Appendix B Service Status Codes	A summary list of the status codes, and their causes, that can be returned by each of the operations forming the service. These describe the end-to-end status of the transaction.

API	Application Programming Interface
Adaptive/CAT Engine	Engine responsible for selecting next item(s) to present to the candidate based on the data provided.
AfAPNP	Access for All Personal Needs and Preferences
CAT	Computer Adaptive Testing
Candidate	The individual taking the (adaptive) test.
GUID	Globally Unique Identifier
ISO	International Standards Organization
Item Pool	The pool of items the Adaptive Engine can select from to present to the candidate.
JSON	JavaScript Object Notation
LUID	Locally Unique Identifier
PNP	Personal Needs and Preferences
QTI	Question and Test Interoperability
REST	Representational State Transfer
Section	A section of the test that can be configured to be adpative.
Session	The period in which the candidate is taking the test.
Test Driver/Test Delivery Engine	Test Delivery Engine responsible for the presentation of the graphical user interface and test content.
UML	Unified Modeling Language
URI	Uniform Resource Identifier
URL	Uniform Resource Locator
XML	Exchange Markup Language
XSD	XML Schema Definition

Name:	endSession ()
Return Function Parameter:	imsx_StatusInfo : imsx_StatusInfo - the status information report for the request. This report has end-to-end significance and must map between the messaging technology approach and the business transaction API.
Supplied (in) Parameters:	sectionIdentifier : LUID - the LUID that identifies the Section to be deleted on the CAT Engine. sessionIdentifier : LUID - the LUID that identifies the Session, in the context of the identified Section, to be deleted on the CAT Engine.
Returned (out) Parameters:	None.
Behavior:	This request ends the candidate session. The sessionIdentifier, and the sessionState returned from any previous request in the session, become invalid. The delivery engine should not make any further requests related to the session. For a REST-based binding this request uses the DELETE HTTP method because of REST conventions; but it is not required that CAT engines physically delete data or resources associated with the session. If the identified session cannot be found then the 'unknownobject' status code must be reported.

Name:	submitResults ()
Return Function Parameter:	imsx_StatusInfo : imsx_StatusInfo - the status information report for the request. This report has end-to-end significance and must map between the messaging technology approach and the business transaction API.
Supplied (in) Parameters:	sectionIdentifier : LUID - the LUID that identifies the Section in the CAT Engine to be used. sessionIdentifier : LUID - the LUID that identifies the Session, in the context of the Section, in the CAT Engine to be used. resultSet : Results - the set of results that have been obtained, so far, by the examinee for the identified session.
Returned (out) Parameters:	nextItems : NextItemSet - the next set of Items to administer to this examinee. assessmentResult : AssessmentResult - the assessment results but these are usually only at the end of the session when there are no next items to administer. sessionState : SessionState - the session state to send back on subsequent calls within this session.
Behavior:	This request sends the results from the current item stage in a candidate session to the CAT engine. The CAT engine returns its computed outcome variable values for the current stage and the test as a whole. It also returns the next item stage to be presented to the candidate. Instead of the next item stage, it may also return an indication that the adaptive section has ended, by returning an empty list for nextItems. If the identified Section/Session cannot be found then the 'unknownobject' status code must be reported.

Descriptor	Definition
Attribute Name	sourcedId
Data Type	LUID
Value Space	Container [ DerivedType ]
Scope	Local ("-")
Multiplicity	[0..1]
Description	A unique identifier for the test candidate.

Descriptor	Definition
Attribute Name	sessionIdentifiers
Data Type	SessionIdentifier
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	The system that creates the result (for example, the test delivery system) should assign a session identifier that it can use to identify the session. Subsequent systems that process the result might assign their own identifier to the session which should be added to the context if the result is modified and exported for transport again.

Descriptor	Definition
Class Name	CorrectResponse
Class Type	Container [ Sequence ]
Parents	The set of parent classes are: ResponseVariable
Derived Classes	There are no derived classes.
Super Classes	This class is not derived from another class.
Characteristics	There are no characteristics.
Children	The set of children attributes are: interpretation value
Description	The correct response may be output as part of the report if desired. Systems are not limited to reporting correct responses declared in responseDeclarations. For example, a correct response may be set by a templateRule or may simply have been suppressed from the declaration passed to the delivery engine e.g. for security.

Descriptor	Definition
Attribute Name	interpretation
Data Type	String (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	A human readable interpretation of the correct value.

Descriptor	Definition
Attribute Name	identifier
Data Type	LUID
Value Space	Container [ DerivedType ]
Scope	Local ("-")
Multiplicity	[1]
Description	The identifier of the item for which this is a result. For item results that are reported as part of a test result this is the identifier used to refer to the item in the test (see assessmentItemRef). For item results that are reported on their own, this can be any suitable identifier for the item. Where possible, the value should match the identifier attribute on the associated assessmentItem.

Descriptor	Definition
Attribute Name	sequenceIndex
Data Type	NonNegativeInteger (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	For item results that are reported as part of a test, this attribute must be used to indicate the position of the item within the specific instance of the test. The first item of the first part of the test is defined to have sequence index 1.

Descriptor	Definition
Attribute Name	datestamp
Data Type	DateTime (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[1]
Description	The date stamp of when this result was recorded.

Descriptor	Definition
Attribute Name	sessionStatus
Data Type	SessionStatus
Value Space	Enumerated value set of: { final \| initial \| pendingResponseProcessing \| pendingSubmission }
Scope	Local ("-")
Multiplicity	[1]
Description	The session status is used to interpret the values of the item variables. See the sessionStatus vocabulary.

Descriptor	Definition
Attribute Name	responseVariables
Data Type	ResponseVariable
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	Indicates that a Response Variable is being reported. This is the value of one of the responses associated with an Item in the corresponding ASI instance.

Descriptor	Definition
Attribute Name	templateVariables
Data Type	TemplateVariable
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	Indicates that a Template Variable is being reported. This is the value of one of the template variables associated with an Item in the corresponding ASI instance.

Descriptor	Definition
Attribute Name	outcomeVariables
Data Type	OutcomeVariable
Value Space	Container [ Sequence ]
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	Indicates that an Outcome Variable is being reported. This is the value of one of the outcomes associated with either an Item or Test and defined in the corresponding ASI instance.

Descriptor	Definition
Attribute Name	candidateComment
Data Type	String (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	An optional comment supplied by the candidate (see the allowComment in the ASI documentation [QTI, 20a]).

Descriptor	Definition
Attribute Name	glossaryURI
Data Type	AnyURI (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	This is a URI to the definition of the data being supplied in this accompanying key/value pair. This definition should provide a human readable description of the data-type and value space for the value being identified by its key.

Descriptor	Definition
Attribute Name	cardinality
Data Type	CardinalityEnum
Value Space	Enumerated value set of: { multiple \| ordered \| record \| single }
Scope	Local ("-")
Multiplicity	[1]
Description	The cardinality of the Outcome Variable, taken from the corresponding declaration or definition.

Descriptor	Definition
Attribute Name	baseType
Data Type	BaseTypeEnum
Value Space	Enumerated value set of: { boolean \| directedPair \| duration \| file \| float \| identifier \| integer \| pair \| point \| string \| uri }
Scope	Local ("-")
Multiplicity	[0..1]
Description	The base type of the Outcome Variable, taken from the corresponding declaration of definition. This value is omitted only for variables with record cardinality.

Descriptor	Definition
Attribute Name	view
Data Type	ViewEnum
Value Space	Enumerated value set of: { author \| candidate \| proctor \| scorer \| testConstructor \| tutor }
Scope	Local ("-")
Multiplicity	[0.. unbounded]
Description	The views (if any) declared for the outcome must be copied to the report to enable systems that render the report to hide information not relevant in a specific situation. If no values are given, the outcome's value should be considered relevant in all views.

IMS Computer Adaptive Testing (CAT) Service Version 1.0

IMS Public Candidate FinalVersion 1.0

IMS Public Candidate Final
Version 1.0

Descriptor	Definition
Attribute Name	longInterpretation
Data Type	AnyURI (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	An optional link to an extended interpretation of the outcome variable's value.

Descriptor	Definition
Attribute Name	normalMaximum
Data Type	Double (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	The normalMaximum attribute optionally defines the maximum magnitude of numeric outcome variables, it must be a positive value. If given, the outcome's value can be divided by normalMaximum and then truncated (if necessary) to obtain a normalized score in the range [-1.0,1.0]. normalMaximum has no affect on responseProcessing or the values that the outcome variable itself can take.

Descriptor	Definition
Attribute Name	normalMinimum
Data Type	Double (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	The normalMinimum attribute optionally defines the minimum value of numeric outcome variables, it may be negative.

Descriptor	Definition
Attribute Name	masteryValue
Data Type	Double (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	The masteryValue attribute optionally defines a value for numeric outcome variables above which the aspect being measured is considered to have been mastered by the candidate.

Descriptor	Definition
Class Name	PCIContext
Class Type	Container [ Sequence ]
Parents	The set of parent classes are: QTIMetadata
Derived Classes	There are no derived classes.
Super Classes	This class is not derived from another class.
Characteristics	There are no characteristics.
Children	The set of children attributes are: customTypeIdentifier interactionKind
Description	This is the container for the contextual information that can be supplied for a PCI used within an Item. The contained information is only relevant when there is an 'interactionType' of 'portableCustomInteraction'.

Descriptor	Definition
Attribute Name	customTypeIdentifier
Data Type	NormalizedString (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	This is used alongside an 'interactionType' value of 'portableCustomInteraction' to disambiguate which class of PCI is in use as PCIs can vary widely in terms of how they might need to be psychometrically analyzed. This field could potentially also be used to identify which type of a traditional customInteraction is in use by the item.

Descriptor	Definition
Attribute Name	interactionKind
Data Type	NormalizedString (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	This is used to provide insight into the nature of the PCI e.g. this is a PCI which allows a user to add notes to a musical stave to author some music that might be given a description of 'authoring'. This information could be used by a psychometrician, etc. as an indication of a similar type of standard interaction.

Descriptor	Definition
Attribute Name	itemTemplate
Data Type	Boolean (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	True if the item is actually an item template, in other words, the item changes its appearance based on some random or external factor. An assessmentItem that contains a templateProcessing section.

Descriptor	Definition
Attribute Name	timeDependent
Data Type	Boolean (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	Whether or not the item is time dependent. A time dependent item takes the length of time taken for an attempt into consideration when scoring.

Descriptor	Definition
Attribute Name	composite
Data Type	Boolean (Primitive-type)
Value Space	See Appendix A3.3.
Scope	Local ("-")
Multiplicity	[0..1]
Description	True if the item comprises more than one interaction, for example, an assessmentItem that contains more than one interaction.