Section author: Matt Windsor<matt.windsor@ury.org.uk>
This is a brief overview of the structure of the LASS project as a whole, including its sub-apps.
In cases where the current state of the code differs from this outline, the code takes precedence. LASS is a constantly changing beast, and thus this can go out of date very quickly.
Often, LASS has needed to reinvent things that Django or existing applications already do.
The usual reason for this is that it is very important that LASS’s database usage plays fair with existing URY applications both legacy and new, and thus the tendency is to eschew any system that would introduce “djangoisms” into the database. This includes things like content-types, MySQL-style prefixed tables (URY runs PostgreSQL), as well as the desire for LASS to be able to use URY’s database table naming conventions where possible.
Usually when it comes to things that LASS doesn’t need to share with other applications, our main philosophy is to reuse where possible, which is why LASS pulls in a large amount of external apps at the website level.
Another reason is that we’re only human, and genuinely might have overlooked a better solution!
Most of LASS is implemented in a few highly generalised apps, which provide a class framework for the higher levels of the system to use.
These are referred to here, with documentation links, in a vague order from low-level to high-level. Usually items referenced lower down the list will have dependencies on packages higher up.
The “root” of the system is the django-lass-utils app, which is intended to have no other dependencies from the LASS project.
The utils app contains a large amount of extremely general mixins and other features used by practically everything else, including:
The documentation for django-lass-utils is here.
Large amounts of data in LASS are tied to people, for example show credits, data change approval, metadata creators and so on. The django-lass-people app provides mixins, models and other items for dealing with these.
The documentation for django-lass-people is here.
A large part of the LASS backbone is the django-lass-metadata app, which implements a general metadata system using the AttachableMixin from django-lass-utils that can be used to attach typed key-value metadata (with history and both single and multiple-value support) to arbitrary models.
It also provides, through MetadataSubjectMixin, a very simple API for accessing metadata that has been attached to models. Often, currently valid metadata can be accessed as if it was an attribute on the model, making transition to and from the metadata system easy.
LASS uses this nearly everywhere where items of data need titles, descriptions, tags, attached images, or internal notes.
The documentation for django-lass-metadata is here.