Persistence Layer¶

The persistence layer forms the heart of crunch_uml: a standardized metaschema stored via SQLAlchemy ORM with multi-version support.

Architecture¶

graph TB
    subgraph Persistentie
        DB["Database (db.py)<br/>Singleton + SQLAlchemy 2.0"]
        SCH["Schema (schema.py)<br/>Multi-version isolation"]
        ORM["ORM Models"]
    end

    DB --> SCH
    SCH --> ORM

    subgraph Backends
        SQLite[("SQLite")]
        PG[("PostgreSQL")]
        MySQL[("MySQL")]
    end

    DB --> SQLite & PG & MySQL

Database Class¶

Singleton implementation that guarantees one active connection per process.

Database(db_url=const.DATABASE_URL, db_create=False)
    .session          # SQLAlchemy session
    .engine           # SQLAlchemy engine
    .commit()         # Commit changes
    .rollback()       # Rollback transaction
    .close()          # Close session
    .add(obj)         # Add new object
    .save(obj)        # Save/merge object

Default database URL: sqlite:///crunch_uml.db

Schema Class¶

Wrapper around a logical schema in the database. Enables multi-version models in one database via schema_id on all tables.

Schema(database, schema_name=const.DEFAULT_SCHEMA)
    .add(obj, recursive=False)           # Add to schema
    .save(obj, recursive=False)          # Save/merge in schema
    .get_package(id)                     # Get package
    .get_class(id)                       # Get class
    .get_all_packages()                  # All packages
    .get_all_classes()                   # All classes
    .count_package()                     # Count packages
    .clean()                             # Delete everything in schema

ORM Models¶

All models inherit from UML_Generic and optionally UMLBase and UMLTags* mixins. See Data Model for the complete entity-relationship diagram.

Model Overview¶

Model	Table	Important Fields
Package	`packages`	id, name, parent_package_id, schema_id
Class	`classes`	id, name, package_id, is_datatype
Attribute	`attributes`	id, name, clazz_id, primitive, enumeratie_id
Association	`associations`	id, src_class_id, dst_class_id, multiplicities
Generalization	`generalizations`	id, superclass_id, subclass_id
Enumeration	`enumeraties`	id, name, package_id
EnumerationLiteral	`enumeratie_literals`	id, name, enumeratie_id
Diagram	`diagrams`	id, name, package_id

Junction Tables¶

Table	Connects
`diagram_classes`	Diagram ↔ Class
`diagram_enumerations`	Diagram ↔ Enumeration
`diagram_associations`	Diagram ↔ Association
`diagram_generalizations`	Diagram ↔ Generalization

Mixins¶

graph TB
    UG["UML_Generic<br/>id, schema_id, name, definitie,<br/>bron, toelichting, created, modified, stereotype"]
    UB["UMLBase<br/>author, version, phase, status,<br/>uri, visibility, alias"]
    UTC["UMLTagsClazz<br/>MIM tags, GEMMA tags"]
    UTA["UMLTagsAttr<br/>Attribute-specific tags"]

    UG --> UB
    UB --> UTC
    UB --> UTA

Planned Extensions¶

Caching & Validation Engine

Cache mechanism for stored validations so that not every validation has to run completely from scratch.

Indexing Techniques

Full-text indexing, fuzzy indexing, and AI-based indexing for more efficient queries on large models.

Centralized Repository

Hierarchically documented metaschema with unique identifiers for relationships.