6. data model

One of the primary goals for mudpy is to apply a consistent data model for all information, from configuration and preferences to user accounts and world data. Individual pieces of information are called facets, and are grouped together into entities called elements. Elements are meant to be treated as loosely-typed objects (if it walks like a duck and talks like a duck…), while facets within them have predefined names and are strictly typed. This combination provides the ability to have facet inheritance among elements as a layered sieve.

The mudpy data model consists of a mix of persistent data (stored externally but cached in memory), and ephemeral data (cross-reference indexes which can be regenerated from it). For now, persistent data is stored externally in a tree-like hierarchy of text files starting from a main configuration usually named mudpy.yaml and cached in memory as a single python dict known as the universe. This default implementation, while memory-hungry, is planned so as to reduce the number of dict lookup operations performed to retrieve an individual piece of information, when compared with a more deeply-nested dict model.

6.1. groups

The universe is organized with a hierarchical namespace using the period (.) symbol as a separator. It is rooted at . and grows to the right with successive nodes. The right-most node must always be a facet, and the remainder of the series thus denotes the absolute name of an element within the universe (the second node from the right being the relative element name and the remaining nodes to the left are called the group). Near the root of the universal namespace are a number of special elements anchored within the .mudpy branch which provide necessary configuration information and keeps some basic elements from cluttering the rest of the tree.

6.1.1. .mudpy.actor

Where new actor elements with no specified storage destination are kept by default.

6.1.2. .mudpy.archetype

Where the default archetype definitions are grouped together.

6.1.3. .mudpy.command

Where the default command definitions are grouped together.

6.1.4. .mudpy.data

Defines default long-term storage locations for various element groups.

6.1.5. .mudpy.facet

Defines default values and validation checks for every facet.

6.1.6. .mudpy.filing

Defines filesystem-based backend storage meta data.

6.1.7. .mudpy.linguistic

Language specific configuration.

6.1.8. .mudpy.limit

Various aspects determining mudpy performance.

6.1.9. .mudpy.log

Configuration for logging.

6.1.10. .mudpy.menu

Where the default menu definitions are grouped together.

6.1.11. .mudpy.movement

Defines movement directions.

6.1.12. .mudpy.network

Network socket configuration.

6.1.13. .mudpy.process

Process-specific configuration.

6.1.14. .mudpy.prop

Where new prop elements with no specified storage destination are kept by default.

6.1.15. .mudpy.room

Where new room elements with no specified storage destination are kept by default.

6.1.16. .mudpy.timing

Timing-specific settings and scheduling for the main loop.

6.2. storage

Long-term storage is accomplished with YAML format files, consisting of an associative array of keys mapped to values of various data types. The keys can be either absolute (beginning with a . character) or relative to the anchor specified by the parent file which loaded it. Special records can also exist to describe a data file’s properties, and always begin with an underscore (_). These are stored in the universe under the .mudpy.file group with elements named for escaped versions of the file path (. and : replaced by \. and \:) and the underscore stripped from the beginning of each facet.

6.2.1. _copy

Arbitrary string providing copyright notice and license information.

6.2.2. _desc

Arbitrary string containing a description of the file or any other useful information worth noting.

6.2.3. _load

List of additional data sources to load and where to anchor their elements in the universe. The value is prefaced by the storage medium separated from the remainder by an optional parenthetical parameter and a colon. The only type implemented so far is file and the optional parameter is p to indicate a private file which should only be readable by the account under which the process is running rather than created with the default umask (ignored on unsupported platforms).

6.2.4. _lock

Boolean value indicating read-only status. Any file not protected with a _lock record will be regenerated and rewritten by mudpy if its records are changed, so record format will be normalized, records arbitrarily reordered and YAML comments lost in the process.