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Analysis

Overview

This group of tasks is about improving the base.persistence module and providing the new R3 resource format. After this task is complete, the following will be true:

• The base.persistence module will provide all the commons needed for persistence.
• The R3 format will be a Resource format, not just a Book format. This means that any kind of Resource (Book, Page, Frame etc..) could be saved in this format.
• Functionality for saving Immutables and ProObjects (Resources, in particular) will be present.
• An intermediate storage format will exist.
• Extensions and extension points for simplifying the usage and improving extensibility of the format.

Task requirements

The R3 format replaces the R2 format. These are the goals of these task:

• The R2 format is a file format for saving a given Book. Compared to it, the R3 format is a Resource format - it should be capable of saving any given Resource.
• This Resource-oriented format gives features that should be taken in mind when implementing it:
  • In future it should allow saving/loading any Resource - Frame, Page, Annotation. This will be very useful if we consider Frame/Page editor for example. It would be also useful for saving templates.
• Improve machine and human readability of the format:
  • XML aspect - redesign the used XML tags to be both human and machine readable.
  • File structure - create a good and consistent structure inside the archive.
  • Data standards - what goes where:
    • XML aspect - XML should contain Immutables and metinfo. Define where does it belong in the structure
    • Binary data - define location of the binary data for each ProObject (Resources in particular).
    • Text data - define how to handle text contents; where to store them and in what form.
• Define how a Resource is located and accessed (ID, local path, URL).
• Support caching and offline content - currently cache mechanism doesn't exust. The file format needs to support cache and ability to save online resources.
  • Caching however should be limited. In future releases we may consider GUI input for the limit, for example "100MB"
• Make the R3 format backward compatible with R2:
  • The application should be able to load a book in R2 format and save it to R3 format.
  • Optional - achieve saving a book in R2 format. This doesn't need to have GUI for saving in R2 but there may be a mechanism for converting R3 to R2.
• Support of saving online content. This may not be implemented now, but in future we may have to support downloading online Resources and saving them into the book.
• Also in the future, we need to refactor the Storage in order to implement lazy loading of Resources (and Resource preview, respectively).

Task result

• Source code
• Wiki content

Implementation idea

Define a tree structure and divide the book into folders.

• Each resource has its own folder and contains sub-folders of its subresources.
• Each folder contains an XML with properties (immutables) and information for the specific resource, and information about the subresources. The folder should also contain the binary data of the resource.
• The book's folder has a subfolder for cache. Consider should resources have own cache directory or all should use the book cache directory.
• Implement the annotations that were discussed - @Persist, @Immutable (see the video of the discussion for more information on these):
  • An annotation for entities not to be persisted might be needed.
  • (Optional) Provide a class that handles all Immutables coming from the JDK.
• Design and implement a format registry that keeps track of all formats and their features and limitations:
  • see BASE_PERSISTENCE_FORMAT_REGISTRY_R0 for more ideas on that.
• Ensure backward compatibility.
• Consider forward compatibility in the design.

Related

GROUP_RESOURCE_R0
GROUP_CHANGE_R0?
​http://asteasolutions.net/videos/

How to demo

• Explain the ideas of the format.
• Demo saving and loading of various Resources.
• Run the tests/demos.
• (Optional) Show the created wiki page.

Design

R3 Format Structure

Code Structure

Storage

Persistor <S, T>

Loader <T>

PersistorRegistry

Core Persistors

• MasterPersistor
• ProObjectPersistor
• ImmPersistor

Annotations

• @Persist
• @PersistBy
• @PersistList

Implementation

^{Describe and link the implementation results here (from the wiki or the repository).}

Testing

^{Place the testing results here.}

Comments

^{Write comments for this or later revisions here.}