Content Hosting (CH) is currently implemented via a two-tier set of objects: one to store content and properties in a datbase, the other to store content in files. If content is saved in files and properties are kept in the database, this presents a serious problem with resource integrity. For example, if a file is deleted in Sakai, and the user asks their IT people to restore it, the metadata is lost, potentially corrupting the Content Hosting system. Also, the implementation uses an internally defined method of naming files and directories that makes restoring files nearly impossible.
Given a desire to support restoring lost files and external file system management (via AFS, etc.), I am exploring a new implementation of Content Hosting based solely on a standard file system. Naturally, there are trade-offse with this approach. It may not be as fast as the existing implementation, and some way needs to be found to associate base files with their metadata files. Coupled with this is a desire (expressed by some) to implement some form of JSR-170.
See also, CH Project Notes
Planned Approach
- Map directory names and file names directly to an underlying (specified) file system.
- Save properties in a file called file-name.properties, where file name corresponds to the base file name.
- Save attachement references in a file called file-name.attachments.
Identifiers
Content resources are identified by a file name. In most cases, this name will have a file extention separated by a period, from which the MIME type may be deduced (via an extention map). All files also have a metadata file associated with it named the same, with a file extension of .properties. These properties may optionally be cached in a database to allow faster access to them.
Resources may have attachemnts - how will these be identified? How will they be kept together with their resource?
All resources (and attachments) live in a collection. Resource identifiers must be unique within the collection they live in. Collections may contain sub-collections. Collections are simply named and correspond to directories in a file system. Collection names must be unique within the collection they live in.
Collection paths are defined against a local root. This root is associated with a context (usually a site). Local roots branch from a Sakai global root, which in turn is mapped to a file system location. Context specific roots cause problems, however. Unless the context is included in a resource or collection id, it is no longer globally unique. This might not be a problem as long as methods that resolve against the id are done in the current context.
Things To Do
Item |
Status |
Notes |
|---|---|---|
Resource metadata |
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Collection metadata |
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Attachments |
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Need to figure out how to include these. |
Attachment metadata |
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File types |
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Need a mapping function. |
Drop Box |
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Has this been changed for 2.2? |
Project Status
Based implementation of resources and collections have begun. Interfaces have been copied locally to the ContentTool to simplify things for the interrim. As the implementations approach the full API specifications, the real APIs will be referenced. This is especially true of the ContentHostingService, which has many, many methods.
The APIs are sorta mid-way between Sakai 2.1 and 2.2. I need to create a sandbox in the 2.2 world and start referring to the new package names for ContentHosting. I'm holding off until I do the initial check in to contrib before making these changes.
Note: Sakai 2.2 defines a ContentEntity.
ContentHostingService Methods
Method Name |
Status |
Notes |
|---|---|---|
getLabel(); |
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willArchiveMerge(); |
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willImport(); |
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archive(); |
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merge(); |
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importEntities(); |
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parseEntityReference(); |
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getEntityDescription(); |
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getEntityResourceProperties(); |
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getEntity(); |
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getEntityUrl(); |
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getEntityAuthzGroups(); |
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getCollection(String id); |
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(many more collection methods) |
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(many resource methods) |
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ContentCollection Methods
Method Name |
Status |
Notes |
|---|---|---|
getUrl(); |
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getReference(); |
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getUrl(root-prop); |
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getReference(root-prop); |
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getId(); |
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getProperties(); |
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toXml(); |
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getMembers(); |
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getMemberResources(); |
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getBodySizeK(); |
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getReleaseDate(); |
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2.2 method |
getRetractDate(); |
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2.2 method |
ContentCollectionEdit Methods
Method Name |
Status |
Notes |
|---|---|---|
isActiveEdit(); |
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getPropertiesEdit(); |
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setReleaseDate(); |
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2.2 method |
setRetractDate(); |
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2.2 method |
ContentResource Methods
Method Name |
Status |
Notes |
|---|---|---|
getUrl(); |
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getReference(); |
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getUrl(root-prop); |
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getReference(root-prop); |
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getId(); |
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getProperties(); |
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toXml(); |
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getContentLength(); |
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String getContentType(); |
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getContent(); |
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getReleaseDate(); |
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2.2 method |
getRetractDate(); |
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2.2 method |
streamContent(); |
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ContentResourceEdit Methods
Method Name |
Status |
Notes |
|---|---|---|
isActiveEdit(); |
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getPropertiesEdit(); |
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setContentLength(); |
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setContentType(); |
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setContent(); |
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setReleaseDate(); |
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2.2 method |
setRetractDate(); |
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2.2 method |
You can track progress via my CH Project Notes.
Things to Do
- Move the work to contrib.
Joining
Send me email if you are interested in participating in this project.