The answersDownload the PDF
Worksheet

A11.8 Capturing, managing and exchanging data

Databases and big data · A level · OCR H446 1.3.2, AQA 7517 4.9.4.10, Eduqas A500QS 2.4 · about 55 min

BugBotLab
NameClassDate

What this lesson is about

How data gets in, how it is selected and managed, and how systems swap it as CSV, JSON and XML. The robot exports its own readings.

Questions 6 marks in all

  1. [1 mark]Exam answer sheets are scanned and the positions of shaded boxes are read. Which capture method is this?

    1. AOptical mark recognition (OMR)
    2. BOptical character recognition (OCR)
    3. CRFID
    4. DA data logger

  2. [1 mark]A run time of 7.2 s is typed as 2.7 s. Which check could catch this?

    1. AVerification, such as double entry
    2. BA range check
    3. CA presence check
    4. DA format check

  3. [1 mark]What does a data dictionary hold?

    1. AData about the data: tables, fields, types, lengths, keys and validation rules
    2. BEvery record in the database, sorted
    3. CA list of the words used in text fields
    4. DBackups of deleted records

  4. [1 mark]Which are true of JSON compared with XML?

    Tick every answer that is true.

    1. AJSON is usually more compact
    2. BJSON has types such as numbers, true and false
    3. COnly XML can represent nested data
    4. DJSON requires every value to be wrapped in opening and closing tags

  5. [1 mark]What does this print?

    import json
text = '{"robot": "Ada", "readings": [61, 51, 41], "ok": true}'
data = json.loads(text)
print(data["robot"], len(data["readings"]), data["readings"][-1] + 1, data["ok"])

  6. [1 mark]What does this print?

    import csv, io
rows = list(csv.reader(io.StringIO("name,cm\nAda,42\nBolt,38\n")))
print(rows[1])
print(rows[1][1] + rows[2][1])

The task: three formats, one set of readings

The robot starts facing a wall. Take four readings, numbered step 0 to 3. For each: record step (a whole number), y (the second value of position(), rounded to 1 decimal place) and cm (the value of distance()), then drive forward 10 cm at speed 40 before the next reading (no drive after step 3). Then, from that one list of readings: 1. Write readings.csv: the header line step,y,cm, then one line per reading, such as 1,10.0,51.0. 2. Write readings.json with json.dump: a list of four objects, each with the keys step, y and cm. 3. Read readings.json back with json.load and print json readings: <n>, the number of objects in it. 4. Print the readings as XML: a line <readings>, then one line per reading exactly in the form <reading step="1" y="10.0" cm="51.0"/> (indenting is allowed), then </readings>.

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

import json

readings = []

Plan your program here, then type it in and press Run.

QR code
Do it on the robot
www.bugbotlab.com/learn/a11-8-capturing-and-exchanging-data/
The simulator checks it and tells you when it passes. Nothing to install, no account.

Challenges

  1. Add a seconds field, the time of each reading from clock(). Which of your three outputs needed changing, and how?
  2. Nest the readings inside a JSON object that also records the robot's name and the date. Could CSV hold the same thing?
  3. A robot's name is Ada, the second. What goes wrong in a CSV file written by hand, and how does the csv module deal with it?