🌐 Week 8 Activity — Exploring APIs and Parameters

🧩 What You’ll Learn

In this activity, you’ll:

Send API requests in your browser and terminal.
Change parameters to see how they affect results.
Record observations about how APIs deliver structured data.

🔍 Quick Refresher: What’s an API?

An API (Application Programming Interface) lets one program request information or perform an action on another system.

When you use a web API, you:

send a request to a URL,
include parameters that specify what you want,
receive a structured response (usually in JSON format).

Example:

https://api.open-meteo.com/v1/forecast
  ?latitude=39.1653
  &longitude=-86.5264
  &hourly=temperature_2m

Part	Meaning
Base URL	`https://api.open-meteo.com/v1/forecast` (the main API endpoint)
Query Parameters	`latitude`, `longitude`, `hourly` (control the output)
Response	JSON data showing forecast values

1️⃣ Wikipedia API (Path Parameters)

Base: https://en.wikipedia.org/api/rest_v1/page/summary/

Try these URLs in your browser or with curl:

Version	URL	What Changed?
Original	https://en.wikipedia.org/api/rest_v1/page/summary/International_Image_Interoperability_Framework
Variation 1	https://en.wikipedia.org/api/rest_v1/page/summary/Albert_Camus	Changed article name
Variation 2	https://en.wikipedia.org/api/rest_v1/page/html/Albert_Camus	Changed endpoint from “summary” to “html”
Variation 3	https://en.wikipedia.org/api/rest_v1/page/summary/ThisArticleDoesNotExist	Invalid title

Reflection:

How does the path parameter (part of the URL path) define what you get?
What happens if you change the endpoint?

2️⃣ Open-Meteo API (Query Parameters)

Base: https://api.open-meteo.com/v1/forecast

Try each variation and observe the differences:

Version	URL	Parameters Added or Changed
Original	https://api.open-meteo.com/v1/forecast?latitude=39.1653&longitude=-86.5264&hourly=temperature_2m	baseline
Variation 1	https://api.open-meteo.com/v1/forecast?latitude=39.1653&longitude=-86.5264&hourly=temperature_2m,relative_humidity_2m	add second variable
Variation 2	https://api.open-meteo.com/v1/forecast?latitude=48.8566&longitude=2.3522&hourly=temperature_2m	change location to Paris
Variation 3	https://api.open-meteo.com/v1/forecast?latitude=39.1653&longitude=-86.5264&hourly=temperature_2m&timezone=America/New_York	add timezone

Reflection:

Which parameters control what vs where vs how results appear?
How could this be useful in your own digital projects?

3️⃣ GitHub API (Pagination Parameters)

Base: https://api.github.com/repos/UniversalViewer/universalviewer/releases

Version	URL	Parameter(s)
Original	https://api.github.com/repos/UniversalViewer/universalviewer/releases?per_page=3	`per_page=3`
Variation 1	https://api.github.com/repos/UniversalViewer/universalviewer/releases?per_page=5	`per_page=5`
Variation 2	https://api.github.com/repos/UniversalViewer/universalviewer/releases?per_page=3&page=2	add `page=2`
Variation 3	https://api.github.com/repos/IIIF/api/releases?per_page=3	change repository

Reflection:

How do per_page and page control how much data you see?
What stays constant (the endpoint)? What changes (the parameters)?

4️⃣ JSONPlaceholder (Path, Query, and Body Parameters)

Base: https://jsonplaceholder.typicode.com/todos

Version	Method	Example	Parameter Type
GET single record	Browser	https://jsonplaceholder.typicode.com/todos/1	path
Filtered list	Browser	https://jsonplaceholder.typicode.com/todos?userId=2	query
POST new record	Terminal	`curl -s -X POST https://jsonplaceholder.typicode.com/posts -H "Content-Type: application/json" -d '{"title":"hello api","body":"this is a demo","userId":1}'`	body

Reflection:

How does a query parameter differ from a path parameter?
Which method (GET or POST) reads data vs creates data?

5️⃣ NASA Astronomy Picture of the Day (JSON vs XML Formats)

Base: https://api.nasa.gov/planetary/apod

This API returns information about NASA’s “Astronomy Picture of the Day.”
It’s free to use for small-scale demos — just include the public key api_key=DEMO_KEY.

Step 1 — Try It in Your Browser

Version	URL	Parameters Used
JSON (default)	https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY	`api_key=DEMO_KEY`
XML format	https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY&format=xml	add `format=xml`
JSON for a specific date	https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY&date=2020-01-01	add `date=2020-01-01`
XML for a specific date	https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY&format=xml&date=2020-01-01	add `format=xml` + `date=2020-01-01`

Step 2 — Try It in the Terminal (Optional)

# JSON (default)
curl -s "https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY"

# XML version
curl -s "https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY&format=xml"

# Specific date (e.g., Jan 1, 2020)
curl -s "https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY&format=xml&date=2020-01-01"

Step 3 — Observe and Compare

Format	What Does the Data Look Like?	How Are Fields Marked?
JSON	`{ "title": "...", "date": "...", "url": "..." }`	key:value pairs
XML	`<title>...</title>`	nested tags

Reflection

Which format (JSON or XML) is easier for you to read as a human?
Which format might be easier for a computer to parse? Why?
Why might digital libraries or archives offer both formats?
(Hint: legacy systems and metadata standards often use XML.)
What parameter controls the format of the response?
How could a project like IIIF or CollectionBuilder make use of an API that supports multiple formats?

✅ Goal: Recognize that APIs can offer the same content in multiple data formats through parameters.
You’ve now seen JSON (structured for JavaScript and modern apps) and XML (widely used for metadata and archival interchange). —

6️⃣ Library of Congress Digital Collections API (Library/Archive Example)

Base: https://www.loc.gov/

The Library of Congress exposes its collections and metadata through a public API—no key required!

Step 1 — Try It in Your Browser

Version	URL	Parameters Used
JSON (default)	https://www.loc.gov/collections/?q=comic+books&fo=json	`q=comic+books`, `fo=json`
XML	https://www.loc.gov/collections/?q=comic+books&fo=xml	change `fo` to `xml`
Limit results	https://www.loc.gov/collections/?q=comic+books&fo=json&c=3	add `c=3`
Filter to photographs	https://www.loc.gov/collections/?q=indiana&fa=original-format:photograph&fo=json	add `fa=original-format:photograph`

Step 2 — Try It in the Terminal (Optional)

# JSON response
curl -s "https://www.loc.gov/collections/?q=comic+books&fo=json"

# XML response
curl -s "https://www.loc.gov/collections/?q=comic+books&fo=xml"

Step 3 — Observe and Compare

Format	What Does the Data Look Like?	How Are Fields Marked?
JSON	`"title": "..."`, `"date": "..."`	key:value pairs
XML	`<title>...</title>`	nested tags

Reflection

What parameter changes the format of the response?
How are search terms and filters expressed in the URL?
What kinds of metadata fields appear in the results (title, date, subject)?
How could this API support a digital exhibit or research collection?
How is this similar to IIIF in allowing machine-to-machine access?

✅ Goal: See how a real library API exposes collection metadata in both JSON and XML—perfect for connecting technical skills to digital-library practice.

🧠 Wrap-Up Questions

What is a parameter in the context of an API request?
How does changing parameter values affect the data you receive?
Which APIs you tried today could support your own digital collections or research projects (e.g., IIIF, weather, Wikipedia)?
Why do digital library tools like IIIF rely on well-structured APIs?