Granularity
Granularity† of digital learning resources refers to size, decomposability and the extent to which a resource is intended to be used as part of a larger resource.
A related term is aggregation level†, which is used in IEEE Learning Object Metadata (LOM) to describe “the functional granularity” of a learning object. The IEEE LOM Standard (IEEE LOM, 2002) is used in the learning technology community and is incorporated into other specifications and standards [Standards Primer]. IEEE LOM offers the following scale for aggregation level:
- The smallest level of aggregation, e.g. raw media data or fragments.
- A collection of level 1 learning objects, e.g. a lesson.
- A collection of level 2 learning objects, e.g. a course.
- The largest level of granularity, e.g. a set of courses that lead to a certificate.
A point made by the LOM scale is that file size may not be tightly coupled with granularity. For example, an image (LOM aggregation level “1”) may be several megabytes in size, whereas a lesson that incorporates that image using a link (LOM aggregation level “2”) may be only a few kilobytes.
Granularity and Content Models
Granularity, or aggregation level, is important in defining and determining reusability. For an image, reusability means the ability to use the entire image in another setting. For an entire online course, reusability often refers to the ability to use parts of the course.
The Learnativity Foundation has developed a content model or aggregation model (Wagner, 2002) that is useful for describing granularity.
| Granularity | Explanation |
|---|---|
| Content Asset | Raw media: Images, text snippets, audio clips, applets, etc. |
| Information Object | A text passage, Web page(s), applet, etc. that focuses on a single piece of information. It might explain a concept, illustrate a principle, or describe a process. [Single] exercises are often considered to be information objects. |
| Learning Object | In the Learnativity content model a Learning Object is a collection of Information Objects that are assembled to teach a single learning objective [see below]. |
| Learning Component | A learning component is a generic term for things like lessons and courses that typically have multiple learning objectives and are composed of multiple learning objects. |
| Learning Environment | “Learning Environment” is a catch-all phase for the combination of content and technology with which a learner interacts. Thus a course written in a course management system is a learning component, but a deployment of the course in a live Course Managemnet System at a particular institution (with a particular enrollment policy, help center, library reserve system, etc.) is a learning environment. |
The Learnativity Aggregation model blends pedagogic and technical perspectives. The idea of an information object is based on earlier work on learning and structured writing by Robert Horn (Horn, 1993).
The term learning objective† (used to define a learning object) is an instructional design concept that derives from the work of Robert Frank Mager (Mager, 1997), Robert Gagne (Gagne, 1985), Walter Dick and Lou Carey (Dick & Carey, 1996) and others. A learning objective is a single measurable (or verifiable) step on the way to a learning goal. Learning objectives say what a learner is expected to do or learn and how an acceptable level of achievement will be verified. They can come from the psychomotor, affective and cognitive domains and can range from knowledge and comprehension to synthesis and evaluation (see Bloom’s taxonomy (Bloom, 1956)).
Themes found in Clark’s writings(Clark, 1998) and in a corporate training white paper published by Cisco Systems (Barritt & Lewis, 2000) are developed in the Learnativity model. It has gained considerable acceptance in both the training and education communities. The following diagram, reprinted with permission from (Wagner, 2002), shows the above model in graphical format.
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Granularity, Decomposability and Reuse
Each level of granularity has a different inherent degree of ability to be decomposed† into more granular pieces, and each level of granualrity has different inherent expectations for reuse. In addition, reuse often refers to components of resources rather than to the entire resource. It is therefore necessary to scope judgments concerning reusability to the granularity of the resource being examined. The following table is intended to aid in this regard.
| Granularity | Decomposability | Reuse |
|---|---|---|
| Content Asset † | Indecomposable | Content assets are reused as is, possibly with modifications in presentation and style. |
| Information Object† | Decomposable into content assets. | Information objects are normally reused as self-contained units. In authoring situations, sometimes, content assets are extracted and reused as well. |
| Learning Object† | Decomposable into content assets and information objects | Learning objects are meant to be reused as self-contained units. Sometimes, information objects or content objects are extracted from a learning object. |
| Learning Component† | Decomposable into learning objects | Learning components can be reused in their entirety, but it is suspected that most reuse of learning components uses only parts of them, usually learning objects. |
| Learning Environment† | Decomposable into content, technology and processes that support learning | The components of learning environments can be reused, but learning environments are not reusable objects in the sense being discussed here. |
Granularity and Standards
Several common learning technology standards deal with aspects of granularity.
The Learnativity model maps onto the IEEE LOM aggregation level scale with both assets and information objects being assigned an aggregation level of “1”, Learnativity learning objects having aggregation level “2”, learning components aggregation level “3” and learning environments aggregation level “3” or “4.”
The most widely implemented set of specifications intended to allow learning content to be developed independently of a particular delivery platform is the Sharable Content Object Reference Model (SCORM)†, a collection of specifications and standards that is documented and maintained by the Advanced Distributed Learning initiative. SCORM includes a content aggregation model that features:
- Assets
- Sharable content objects (SCOs)
- Content aggregations
SCORM assets are content assets and information objects in the Learnativity model. SCOs are self-contained learning objects or learning components that meet additional technical requirements needed for interoperability with learning delivery platforms. A SCORM content aggregation contains assets, SCOs, information on the order in which these should be delivered and metadata about entire aggregation and its individual components. In the Learnativity model, a SCORM content aggregation could be a learning object or a learning component. SCORM uses a technical specification developed by the IMS Global Learning Consortium† to define the format for content aggregations.