Forum .LRN Q&A: Re: Request for advice from the OCT
What is reuse for you?
The assessment system has an item repository, where all items are stored (item = question = smallest entity of an assessment). This repository stores *all* items, so there is no "reuse" in the traditional sense, as *all* items are reused the moment an assessment is generated. Now I assume that your intention is to store these items in an IMS CP tight repository, handled through LORS. I'm not sure what the benefit is, taking into account that all packages use a common content repository to store the content and IMS CP seems to be a way to distribute courses and course elements as a package for interchange between applications. It should therefore be the main goal to be able to import/export content from IMS CP. And if I'm not utterly mistaken, the concrete packaging of assessments is defined in IMS QTI, which we import and export already (thanks to Eduardo and Alvaro).
Your idea for the focus is a description which I can agree to. The main question though remains, how are we going to solve the issues technically. Taking the OpenACS approach, we store the content in the content repository, regardless of the packaging described in Standards, and offer an API that allows us to import/export the data according to these standards. Taking into account that assessment is used in a variety of use cases which have nothing to do with IMS specifications (see the use cases at http://cvs.openacs.org/cvs/*checkout*/openacs-4/packages/assessment/www/doc/requirements.html), my understanding is it is sufficient to have import/export functionalities.
But I have the slight feeling I'm missing something that others read in the specifications, that make it more useful to use IMS compliant packages than the ones provided by OpenACS. Can someone maybe give me the data model of a LORS ressource, which I could make into an item for assessment? The data model for items is based on the CR and split up into multiple objects, closely linked to each other for a number of (technical) reasons. You can see the latest version at http://cvs.openacs.org/cvs/*checkout*/openacs-4/packages/assessment/www/doc/as_items.html.
After writing this all up, can someone help me out with some questions:
- How does an IMS CP repository differ from the Content Repository used by OpenACS ?
- Would it make sense to extend the OpenACS content repository by the functionality in which IMS CP differs from CR.
- Looking at ims_cp_items (from the LORS package), a couple of other questions come into my mind (in the background of evaluating if assessment should extend ims_cp_items instead of cr_items, which would be implied by using the IMS CP repository and not the OpenACS Content Repository (pure version)).
- How are additional attributes to ims_cp_items handled? I assume through the metadata definition.
- Should this approach taken there be generalized to allow handling metadata of items in general (of the content_repository), thereby making the extensions to cr_items and useage of your own package tables obsolete?
- If the answer to above is no, under which circumstances should a package store it's content in the LORS CP and what is the benefit compared to using it's own tables / plain content repository ?
- Technical questions (Ernie, please help):
- What is the parameter attribute for?
- How do you store prerequsites? Wouldn't it make sense to use relationships for this ?
- Some varchars suggest you would store XML content in these, is this true (e.g. maxtimeallowed, timelimitaction)
- Is there a specific reason for storing isvisible, as this could be handled through the permission system.
- You seem hesitant to use acs_rels in your system. Is there a reason? (I see a couple of mapping tables).
It is important to acknowledge a couple of things before addressing some of this questions. We tent to think way to much on the tech aspects of the implementation and that's cool. But it is also as important to understand the problem that these specs are trying to tackle.
I'd strongly suggest to have a good thorough read of the specs a bit as it would clarify some of the questions you ask here and also will make you go "ahhh, that's what it is..." sort of feeling.
I know, they are an absolute bi#ch to to follow and they are as dry as a pommie's towel. But nevertheless, they are the best we got. The best practices and implementation guides are probably the best start.
http://www.imsglobal.org/content/packaging/cpv1p1p3/imscp_bestv1p1p3.html
<blockquote> - How does an IMS CP repository differ from the Content Repository
used by OpenACS ?
</blockquote>
This is a big and open question. But let me see if we can summarize it a bit:
OACS CR = stores content
IMS CP = organize and structure content
So, LORSm basically uses the OACS CR to store all the content, and the IMS CP implementation maps all the organization and structure of the content to the actual content.
For instance, an IMS CP item (an entity that could describe a learning unit/object/chapter/etc) is basically an aggregation of content put together to fulfil a specific learning objective (of course without getting very heavily into technicalities and details).
So manifest/organizations/organization/items and to some extent resources, are entities defined for IMS CP that hold structure and organize content in a particular way.
I hope this answers/clarifies the question a bit.
<blockquote> - Would it make sense to extend the OpenACS content repository by the
functionality in which IMS CP differs from CR.
</blockquote>
No. The CR is pretty cool the way it is and that all it needs to do (for storing content).
The IMS CP implementation sits on top, mapping
<blockquote> - Looking at ims_cp_items (from the LORS package), a couple of other
questions come into my mind (in the background of evaluating if
assessment should extend ims_cp_items instead of cr_items, which would
be implied by using the IMS CP repository and not the OpenACS Content
Repository (pure version)).
</blockquote>
??
<blockquote> - How are additional attributes to ims_cp_items handled? I assume
through the metadata definition.
</blockquote>
Metadata is a different set altogether. If for instance an item contains a node of metadata ala:
<item identifier="here_item">
<metadata>
...
</metadata>
</item>
... when I parse the item, I grab the metadata node and pass it to the IMS MD implementation that parses the node and extracts the whole 100+ fields of metadata and maps them into the DB (yeah, it was hell of a mapping).
And this might be *just* the same way as it might work with IMS SS extensions.
<blockquote> - Should this approach taken there be generalized to allow handling
metadata of items in general (of the content_repository), thereby
making the extensions to cr_items and useage of your own package
tables obsolete?
</blockquote>
Although I think that IMS MD has waaay more metadata than any normal human can think of, I wouldn't try to map out all sort of metadata into this schema. Why? well, because you might not need so much. In the implemetnation of IMS MD in LORS, you can specify metadata for any acs_object. So in theory yes, it is possible. However, practically, it might not make a lot of sense.
<blockquote> - If the answer to above is no, under which circumstances should a
package store it's content in the LORS CP and what is the benefit
compared to using it's own tables / plain content repository ?
</blockquote>
The simple answer is: it's done, you don't have to generate 50+ tables in metadata and content packaging entities. It has integration with OACS CR, all IMS CP are acs_objects, exposes the metadata to the search packages (tsearch/tsearch2) and it uses the file-storage for storage and delivery (taking advantage of versioning, permissioning, webdav, etc).
The other best bet you might have would be to manually put your content in the file-storage, creating the folders and then putting all your files in them and liking them together. But then you will miss out on the main purpose of putting this content into packages (the idea of having learning objects)
<blockquote> - What is the parameter attribute for?
</blockquote>
It is for passing parameters to the LMS on runtime. So for instance, if your item points to a resource and this resource has href ="/index", then you can specify parameters to pass to this page when it's requested. For instance if the parameter is "msg=hello", then the LMS should render '/index?msg=hello' as URL.
<blockquote> - How do you store prerequsites? Wouldn't it make sense to use
relationships for this ?
</blockquote>
??
<blockquote> - Some varchars suggest you would store XML content in these, is this
true (e.g. maxtimeallowed, timelimitaction)
</blockquote>
No, I parse XML, get the value for the attribute and put it in the DB. It's all XML, but you just need to extract what you need.
<blockquote> - Is there a specific reason for storing isvisible, as this could be
handled through the permission system.
</blockquote>
Yes it is, as it doesn't mean that you are display the item, but also how it's position is in the sequence (have a look at the best practices doc)
<blockquote> - You seem hesitant to use acs_rels in your system. Is there a reason?
(I see a couple of mapping tables).
</blockquote>
It's not that I've been hesitant, I haven't used them at all. As I mentioned in my previous posting, I still need to play with permissions.
I hope this helps, again, I strongly suggest to have a look at the best practices and implementation guidelines as they might help a lot
Ernie
