Data model definitions are at the core of Rigging, and provide an extremely powerful interface of defining exactly what kinds of input data you support and how it should be validated. The definition of strict types in code is how you navigate the complexity of working with stochastic text in your code. “If the parsing succeeds, I’m now safe to use this data inside my code.”

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Fundamentals

Every model in Rigging should extend the Model base class. This is a lightweight wrapper around pydantic-xml’s BaseXMLModel with some added features and functionality to make it easy for Rigging to manage. In general this includes:
  1. More intelligent parsing for the imperfect text which LLMs frequently provide. Nested tags, unclear sub-structures, multiple models scattered in the text, etc. See the .from_text() method for the details.
  2. A nicer .to_pretty_xml() to get new-line formatted outputs.
  3. Some basic handling for escaping interior XML tags which normally wouldn’t parse correctly.
  4. Helpers to ensure the tag names from models are consistent and automatic.
However, everything pydantic-xml (and by extension normal pydantic) models support is also supported in Rigging.
Background KnowledgeIf you are new to modern python like type hinting and pydantic models, we highly recommend that you familiarize yourself with their documentation. Without this context, many Rigging features may be confusing.

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Primitive Models

Often, you want to indicate to the LLM that it should place a block of text between tags so you can extract only that portion of the message content. 
import rigging as rg

class FunFact(rg.Model):
    fact: str
Pydantic XML refers to these as “primitive” because they have a single field. These models leverage the minimal functionality of XML parsing and take only the contents between the start and end tags.
Parsing for Primitive ModelsWe have a pending task to replace the internals of Pydantic XML parsing to make it more flexible for the kinds of “broken” XML that LLMs frequently produce. Primitive models have special handling in Rigging to make them more flexible for parsing this “broken” XML. If you are having issues with complex parsing, using primitive models is a good option for now.
import rigging as rg

class FunFact(rg.Model):
    fact: str

FunFact(fact="Rigging is pretty easy to use").to_pretty_xml()
# '<fun-fact>Rigging is pretty easy to use</fun-fact>'
Notice that the name of our interior field (.fact) isn’t relevant to the XML structure. We only use this to access the contents of that model field in code. However the name of our model (FunFact) is relevant to the XML representation. What you name your models is important to how the underlying LLM interprets it’s meaning. You should be thoughtful and descriptive about your model names as they affect how well the LLM understands the intention, and how likely it is to output one model over another (based on it’s token probability distribution). If you want to separate the model tag from it’s class name, you specify it in the class construction: 
class FunFact(rg.Model, tag="a-super-fun-fact")
    ...

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Dynamic Primitive Models

If you’d like to define a primitive model functionally, we support an experimental make_primitive() utility. The interior field will always be named .content and typed depending on the argument passed. 
import rigging as rg

FunFact = rg.model.make_primitive("FunFact", str) # (1)!

FunFact(content="Rigging is pretty easy to use").to_pretty_xml()

# <fun-fact>Rigging is pretty easy to use</fun-fact>
1. You can apply most basic types here like bool, int, and float.

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Typing and Validation

Even if models are primitive, we can still use type hinting and pydantic validation to ensure that the content between tags conforms to any constraints we need. Take this example from a default Rigging model for instance: 
from pydantic import field_validator
import typing as t

class YesNoAnswer(Model):
    "Yes/No answer answer with coercion"

    boolean: bool
    """The boolean value of the answer."""

    @field_validator("boolean", mode="before")
    def parse_str_to_bool(cls, v: t.Any) -> t.Any:
        if isinstance(v, str):
            if v.strip().lower().startswith("yes"):
                return True
            elif v.strip().lower().startswith("no"):
                return False
        return v
You can see the interior field of the model is now a bool type, which means pydantic will accept standard values which could be reasonably interpreted as a boolean. We also added a custom field validator to check for instances of yes/no as text strings. All of these XML values will parse correctly into the YesNoAnswer model, so you can handle cases where the LLM outputs a variety of different 
<yes-no-answer>true</yes-no-answer>
<yes-no-answer>False</yes-no-answer>
<yes-no-answer>yes, it is.</yes-no-answer>
<yes-no-answer> NO </yes-no-answer>
<yes-no-answer>1</yes-no-answer>

YesNoAnswer(boolean="true")
YesNoAnswer(boolean=" NO ")
YesNoAnswer(boolean="1")
# ...
The choice to build on Pydantic offers an incredible amount of flexibility for controlling exactly how data is validated in your models. This kind of parsing work is exactly what these libraries were designed to do. The sky is the limit, and everything you find in Pydantic and Pydantic XML are compatible with Rigging.

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Handling Multiple Fields

Unlike vanilla Pydantic, our use of Pydantic XML forces us to think about exactly how models with multiple fields will be represented in XML syntax. Take this as an example: 
class Person(rg.Model):
    name: str
    age: int
In XML this could be any of the following: 
<person name="Will" age=30 />

<person name="Will">
    <age>30</age>
</person>

<person>
    <name>Will</name>
    <age>30</age>
</person>

...
You get the idea. Pydantic XML handles this all very well and offers different ways of defining your fields to specific whether they should be attributes or child elements. You can read more about this in their documentation. The basic rule is this: If your model has more than one field, you need to define every field as either an attribute or an element. How exactly you structure your models and their associated representations is completely up to you. Our general guide is that LLMs tend to work better with elements over attributes. 
class Person(rg.Model):
    name: str = rg.element()
    age: int = rg.element()

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XML Examples

For primitive models, using the default .xml_tags() or .xml_example() works well for communicating to the model how it should respond, however for more complex models it’s highly recommended to overload the .xml_example() method to provide a more detailed example of the XML structure you expect. The easiest way to approach this overload is to instantiate your model class with a few standard values and use .to_prety_xml(). 
import rigging as rg
from typing import Annotated
from pydantic import PlainSerializer

newline_str = Annotated[str, PlainSerializer(lambda x: f'\n{x}\n', return_type=str)] # (1)!

class SaveMemory(rg.Model):
    key: str = rg.attr()
    content: newline_str

    @classmethod
    def xml_example(cls) -> str:
        return SaveMemory(
            key="my-note",
            content="Lots of custom data\nKeep this for later."
        ).to_pretty_xml()

print(f"Use the following format:\n{SaveMemory.xml_example()}")

# Use the following format:
# <save-memory key="my-note">
# Lots of custom data
# Keep this for later.
# </save-memory>
  1. Using pydantic serializer annotations is an easy way to introduce subtle content changes before they are formed into their XML form. Here we’re injecting newlines to make the XML more readable.

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Complex Models

Let’s design a model which will hold required information for making a web request. We’ll begin with an outline of our model: 
class Header(rg.Model):
    name: str
    value: str

class Parameter(rg.Model):
    name: str
    value: str

class Request(rg.Model):
    method: str
    path: str
    headers: list
    url_params: list
    body: str
We’ll start with a few standard string constraints to strip extra white space (which LLMs tend to include) and automatically convert our method to upper case. 
from pydantic import StringConstraints

str_strip = t.Annotated[str, StringConstraints(strip_whitespace=True)]
str_upper = t.Annotated[str, StringConstraints(to_upper=True)]

class Header(rg.Model):
    name: str
    value: str_strip

class Parameter(rg.Model):
    name: str
    value: str_strip

class Request(rg.Model):
    method: str_upper
    path: str_strip
    headers: list
    url_params: list
    body: str_strip
Next we’ll assign our fields to attributes and elements. 
from pydantic import StringConstraints

str_strip = t.Annotated[str, StringConstraints(strip_whitespace=True)]
str_upper = t.Annotated[str, StringConstraints(to_upper=True)]

class Header(rg.Model):
    name: str = rg.attr()
    value: str_strip = rg.element()

class Parameter(rg.Model):
    name: str = rg.attr()
    value: str_strip = rg.element()

class Request(rg.Model):
    method: str_upper = rg.attr()
    path: str_strip = rg.attr()
    headers: list
    url_params: list
    body: str_strip = rg.element()
In terms of handling our headers and URL parameters, we want these to be a list of child elements which are wrapped in a parent tag. We also want these and our body to be optional. 
from pydantic import StringConstraints

str_strip = t.Annotated[str, StringConstraints(strip_whitespace=True)]
str_upper = t.Annotated[str, StringConstraints(to_upper=True)]

class Header(rg.Model):
    name: str = rg.attr()
    value: str_strip

class Parameter(rg.Model):
    name: str = rg.attr()
    value: str_strip

class Request(rg.Model):
    method: str_upper = rg.attr()
    path: str = rg.attr()
    headers: list[Header] = rg.wrapped("headers", rg.element(default=[]))
    url_params: list[Parameter] = rg.wrapped("url-params", rg.element(default=[]))
    body: str_strip = rg.element(default="")
Let’s check our final work: 
Request(
    method="POST",
    path="/api/v1/search",
    headers=[
        Header(name="Authorization", value="Bearer sk-1234")
    ],
    url_params=[
        Parameter(name="max", value="100")
    ],
    body="search=rigging"
)