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UBC CPSC310-20W1: Intro to SE
CHECKPOINT 2
PROJECT SPRINT 2 (C2)
INSIGHTUBC ROOM EXPANSION + QUERY AGGREGATION
Checkpoint 1 built a query engine to answer queries about UBC course sections. This checkpoint will extend the input data to include data about the physical spaces where classes are held on campus. This checkpoint will extend your c1 solution. You will not have to hand anything in; we will automatically analyze your repo on every push between when the checkpoint is released and the due date specified here.
Also, the built query language was fairly simple, as you could not construct queries that would let you aggregate and compute values on the results of queries. In other words, the query engine returned data on a section-by-section basis. This checkpoint will expand the query engine to enable result computation (e.g., to figure out the average for a course or figure out the number of seats for a building).
Important note:
Autobot will create a pull request in your repos during the first week of this sprint. It will contain some changes to your project regarding linting. It is a very good idea to carefully look at this pull request and what Autobot wants to merge into your projects.
CHANGE LOG
DATASET
This data has been obtained from the UBC Building and classrooms listing (although a few years ago). The data is provided as a zip file: inside of the zip you will find index.htm which specifies each building on campus. The links in the index.htm link to files also in the zip containing details about each building and its rooms in HTML format.
The dataset file can be found here: rooms.zip.
Checking the validity of the dataset
A valid dataset:
▪ Has to be a valid zip file; this zip’s root directory will contain many files under a folder called rooms/. This directory name will not vary with the dataset id.
▪ Valid buildings will always be in HTML format.
▪ Missing (i.e. empty string) values found in valid HTML elements are okay.
▪ If a building contains no rooms at all, it can be ignored (you don’t need to keep building-level information).
▪ If a requesting a building’s geolocation results in an error, skip over it.
▪ A valid dataset has to contain at least one valid room that meets the requirements above.
Additionally, in valid zips the following will always be true:
▪ There is a single index.htm file per dataset in the root of the rooms directory of the zip.
▪ All HTML elements and attributes associated with target data will be present in the same forms as in the provided zip file. For example, a
Reading and Parsing the Dataset
As with Checkpoint 1, you will need to parse valid input files into internal objects or other data structures. You must also write a copy of the data structure to disk, and should be able to load these files to be queried if necessary. These files should be saved to the
There is a provided package called parse5 that you should use to parse the HTML files into a more convenient to traverse JSON format (you should only need the parse method). Parse5 also has an online playground where you can see the structure of a Document, which is the output of a parsed HTML file. You must traverse this document in order to extract the building/room information.
You should only parse buildings that are linked to from the index.htm file. There may be more building files in the zip, but they should be ignored.
Other HTML assumptions
▪ You cannot assume that any given HTML file only contains one
▪ HTML elements may exist in different relative locations between different HTML trees.
Finding the geolocation of each building
In addition to parsing the HTML files, you must encode buildings’ addresses to a latitude/longitude pair. This is usually performed using online web services. To avoid problems with our spamming different geolocation providers we will be providing a web service for you to use for this purpose. To obtain the geolocation of an address, you must send a GET request (using the http module) to:
http://cs310.students.cs.ubc.ca:11316/api/v1/project_team
Where ADDRESS should be the URL-encoded version of an address (e.g., 6245 Agronomy Road V6T 1Z4 should be represented as 6245%20Agronomy%20Road%20V6T%201Z4). Addresses should be given exactly as they appear in the data files, or 404 will be returned.
The response will match the following interface (either you will get lat & lon, or error, but never both):
interface GeoResponse {
lat?: number;
lon?: number;
error?: string;
}
Since we are hosting this service it could be killed by DOS attacks, please try not to overload the service. You should only need to query this when you are processing the initial dataset, not when you are answering queries.
To handle the requests, you must use the http package. If you try to update your project with other third party packages AutoTest will fail in unpredictable ways.
QUERY ENGINE
Regarding the query engine, the primary objective of this checkpoint is twofold:
(i) extend the query language to accommodate queries to a new dataset, i.e. rooms; and
(ii) enable more comprehensive queries about the datasets, i.e. aggregate results.
At a high level, the new functionality adds:
▪ GROUP: Group the list of results into sets by some matching criteria.
▪ APPLY: Perform calculations across a set of results.
▪ MAX: Find the maximum value of a field. For numeric fields only.
▪ MIN: Find the minimum value of a field. For numeric fields only.
▪ AVG: Find the average value of a field. For numeric fields only.
▪ SUM: Find the sum of a field. For numeric fields only.
▪ COUNT: Count the number of unique occurrences of a field. For both numeric and string fields.
▪ SORT: Order results on one or more columns.
▪ You can sort by a single column as in C1, e.g., “ORDER”: “courses_avg”; or
▪ You can sort using an object that directly specifies the sorting order (see query example)
▪ “dir”: “UP”: Sort results ascending.
▪ “dir”: “DOWN”: Sort results descending.
▪ “keys”: [“courses_avg”]: sorts by a single key
▪ “keys”: [“courses_year”, “courses_avg”]: sorts by multiple keys
▪ In this example the course average should be used to resolve ties for courses in the same year
EBNF
QUERY ::='{‘BODY ‘, ‘ OPTIONS (‘, ‘ TRANSFORMATIONS)? ‘}’
BODY ::= ‘WHERE:{‘ (FILTER)? ‘}’
OPTIONS ::= ‘OPTIONS:{‘ COLUMNS (‘, ‘ SORT)? ‘}’
TRANSFORMATIONS ::= ‘TRANSFORMATIONS: {‘ GROUP ‘, ‘ APPLY ‘}’
FILTER ::= LOGICCOMPARISON | MCOMPARISON | SCOMPARISON | NEGATION
LOGICCOMPARISON ::= LOGIC ‘:[{‘ FILTER (‘}, {‘ FILTER )* ‘}]’
MCOMPARISON ::= MCOMPARATOR ‘:{‘ mkey ‘:’ number ‘}’
SCOMPARISON ::= ‘IS:{‘ skey ‘:’ [*]? inputstring [*]? ‘}’ // Asterisks should act as wildcards. Optional.
NEGATION ::= ‘NOT :{‘ FILTER ‘}’
LOGIC ::= ‘AND’ | ‘OR’
MCOMPARATOR ::= ‘LT’ | ‘GT’ | ‘EQ’
COLUMNS ::= ‘COLUMNS:[‘ ANYKEY (‘,’ ANYKEY)* ‘]’
SORT ::= ‘ORDER: ‘ (‘{ dir:’ DIRECTION ‘, keys: [ ‘ ANYKEY (‘,’ ANYKEY)* ‘]}’) | ANYKEY
DIRECTION ::= ‘UP’ | ‘DOWN’
ANYKEY ::= key | applykey
GROUP ::= ‘GROUP: [‘ (key ‘,’)* key ‘]’
APPLY ::= ‘APPLY: [‘ (APPLYRULE (‘, ‘ APPLYRULE )* )? ‘]’
APPLYRULE ::= ‘{‘ applykey ‘: {‘ APPLYTOKEN ‘:’ key ‘}}’
APPLYTOKEN ::= ‘MAX’ | ‘MIN’ | ‘AVG’ | ‘COUNT’ | ‘SUM’
key ::= mkey | skey
mkey ::= idstring ‘_’ mfield
skey ::= idstring ‘_’ sfield
mfield ::= ‘avg’ | ‘pass’ | ‘fail’ | ‘audit’ | ‘year’ | ‘lat’ | ‘lon’ | ‘seats’
sfield ::= ‘dept’ | ‘id’ | ‘instructor’ | ‘title’ | ‘uuid’ | ‘fullname’ | ‘shortname’ | ‘number’ |
‘name’ | ‘address’ | ‘type’ | ‘furniture’ | ‘href’
idstring ::= [^_]+ // One or more of any character, except underscore.
inputstring ::= [^*]* // zero or more of any character except asterisk.
applykey ::= [^_]+ // one or more of any character except underscore.
Syntactic Checking (Parsing)
Similar to Checkpoint 1, you must ensure that a query conforms to the above grammar, and reject it if it does not.
Semantic Checking
In addition to the semantic checking from Checkpoint 1, you must perform the following semantic check:
▪ The applykey in an APPLYRULE should be unique (no two APPLYRULEs should share an applykey with the same name).
▪ If a GROUP is present, all COLUMNS terms must correspond to either GROUP keys or to applykeys defined in the APPLY block.
▪ SORT – Any keys provided must be in the COLUMNS.
▪ MAX/MIN/AVG/SUM should only be requested for numeric keys. COUNT can be requested for all keys.
If any of these qualifications are not met, the query is invalid.
Other JS/Typescript considerations
▪ Ordering should be according to the < operator in TypeScript/JavaScript, not by localeCompare.
▪ AVG should return a number rounded to two decimal places. Supporting AVG requires some extra challenges compared to the other operators. Since JavaScript numbers are represented by floating point numbers, performing this arithmetic can return different values depending on the order the operations take place. To account for this, you must use the Decimal package (already included in your package.json), and follow these steps exactly:
1. Convert your each value to Decimal (e.g., new Decimal(num)).
2. Add the numbers being averaged using Decimal's .add() method (e.g., building up a variable called total).
3. Calculate the average (let avg = total.toNumber() / numRows). numRows should not be converted to Decimal.
4. Round the average to the second decimal digit with toFixed(2) and cast back to number type (let res = Number(avg.toFixed(2)))1
▪ SUM should return a number rounded to two decimal places using Number(sum.toFixed(2))1.
▪ COUNT should return whole numbers.
▪ MIN/MAX should return the same number that is in the originating dataset.
1 Once cast to a number, you may appear to "lose" decimal places, for instance Number("2.00") will display as 2. This is okay.
Valid keys
In addition to the valid keys from Checkpoint 1, this checkpoint adds a variety of new keys. A valid query will not contain keys from more than one dataset (i.e. only courses_xx keys or only rooms_xx keys, never a combination).
If the id sent by the user is rooms, then the queries you will run will be using the following keys:
▪ rooms_fullname: string; Full building name (e.g., "Hugh Dempster Pavilion").
▪ rooms_shortname: string; Short building name (e.g., "DMP").
▪ rooms_number: string; The room number. Not always a number, so represented as a string.
▪ rooms_name: string; The room id; should be rooms_shortname+"_"+rooms_number.
▪ rooms_address: string; The building address. (e.g., "6245 Agronomy Road V6T 1Z4").
▪ rooms_lat: number; The latitude of the building, as received via HTTP request.
▪ rooms_lon: number; The longitude of the building, as received via HTTP request.
▪ rooms_seats: number; The number of seats in the room. The default value for this field (should this value be missing in the dataset) is 0.
▪ rooms_type: string; The room type (e.g., "Small Group").
▪ rooms_furniture: string; The room furniture (e.g., "Classroom-Movable Tables & Chairs").
▪ rooms_href: string; The link to full details online (e.g., "http://students.ubc.ca/campus/discover/buildings-and-classrooms/room/DMP-201").
Aggregation (step by step)
First, note that WHERE is completely independent of GROUP/APPLY. WHERE filtering happens first, then GROUP/APPLY are performed on those results.
GROUP: [term1, term2, ...] signifies that a group should be created for every unique set of all N-terms (e.g., GROUP: [courses_dept, courses_id] would create a group for every unique pair of department/id records in the dataset). Every member of a group will always have the same values for each key in the GROUP array (e.g. in the previous example, all members of a group would share the same values for courses_dept and courses_id).
As an example, suppose we have the following courses dataset (for the sake of simplicity, some keys are omitted):
[
{ "courses_uuid": "1", "courses_instructor": "Jean", "courses_avg": 90, "courses_title" : "310"},
{ "courses_uuid": "2", "courses_instructor": "Jean", "courses_avg": 80, "courses_title" : "310"},
{ "courses_uuid": "3", "courses_instructor": "Casey", "courses_avg": 95, "courses_title" : "310"},
{ "courses_uuid": "4", "courses_instructor": "Casey", "courses_avg": 85, "courses_title" : "310"},
{ "courses_uuid": "5", "courses_instructor": "Kelly", "courses_avg": 74, "courses_title" : "210"},
{ "courses_uuid": "6", "courses_instructor": "Kelly", "courses_avg": 78, "courses_title" : "210"},
{ "courses_uuid": "7", "courses_instructor": "Kelly", "courses_avg": 72, "courses_title" : "210"},
{ "courses_uuid": "8", "courses_instructor": "Eli", "courses_avg": 85, "courses_title" : "210"}
]
We want to query the dataset to aggregate courses by their title and obtain their average. Our aggregation query would look like this:
{
"WHERE": {},
"OPTIONS": {
"COLUMNS": ["courses_title", "overallAvg"]
},
"TRANSFORMATIONS": {
"GROUP": ["courses_title"],
"APPLY": [{
"overallAvg": {
"AVG": "courses_avg"
}
}]
}
}
For this query, there are two groups: one that matches "courses_title" = "310" and other that matches "210". At some point you will likely need to have an intermediate data structure to create/hold your groups, use whatever feels natural to you. Continuing with our example, we have these groups:
310 group =
[
{ "courses_uuid": "1", "courses_instructor": "Jean", "courses_avg": 90, "courses_title" : "310"},
{ "courses_uuid": "2", "courses_instructor": "Jean", "courses_avg": 80, "courses_title" : "310"},
{ "courses_uuid": "3", "courses_instructor": "Casey", "courses_avg": 95, "courses_title" : "310"},
{ "courses_uuid": "4", "courses_instructor": "Casey", "courses_avg": 85, "courses_title" : "310"}
]
210 group =
[
{ "courses_uuid": "5", "courses_instructor": "Kelly", "courses_avg": 74, "courses_title" : "210"},
{ "courses_uuid": "6", "courses_instructor": "Kelly", "courses_avg": 78, "courses_title" : "210"},
{ "courses_uuid": "7", "courses_instructor": "Kelly", "courses_avg": 72, "courses_title" : "210"},
{ "courses_uuid": "8", "courses_instructor": "Eli", "courses_avg": 85, "courses_title" : "210"}
]
The last step is fairly simple, we execute the apply operation in each group. Hence, the average of 310 is (90 + 80 + 95 + 85)/4 = 87.5 whereas for the second group the average is 77.25. Our final result for the previous query would be:
[
{ "courses_title" : "310", "overallAvg": 87.5},
{ "courses_title" : "210", "overallAvg": 77.25}
]
Notice that we can have more elaborate groups such as discovering if a specific instructor of a course has a better average than other instructors (i.e.,"GROUP": ["courses_instructor", "courses_title"]). In that cause, we would have four groups 310 - Jean, 310 - Casey, 210 - Kelly, and 210 - Eli.
QUERY EXAMPLE
{
"WHERE": {
"AND": [{
"IS": {
"rooms_furniture": "*Tables*"
}
}, {
"GT": {
"rooms_seats": 300
}
}]
},
"OPTIONS": {
"COLUMNS": [
"rooms_shortname",
"maxSeats"
],
"ORDER": {
"dir": "DOWN",
"keys": ["maxSeats"]
}
},
"TRANSFORMATIONS": {
"GROUP": ["rooms_shortname"],
"APPLY": [{
"maxSeats": {
"MAX": "rooms_seats"
}
}]
}
}
Response:
{
"result": [{
"rooms_shortname": "OSBO",
"maxSeats": 442
}, {
"rooms_shortname": "HEBB",
"maxSeats": 375
}, {
"rooms_shortname": "LSC",
"maxSeats": 350
}]
}
API
There are no changes in the API for this checkpoint, it is the same as the one in Checkpoint 1.
TESTING
There are no changes in the testing instructions, they are the same as in Checkpoint 1. To test C2, call AutoTest with @autobot #c2
ESLINT
Moving forward with the project, we will be using updated ESLint rules.
There are two new major lint rules that will be used.
max-nested-callbacks
Many JavaScript libraries use the callback pattern to manage asynchronous operations. A program of any complexity will most likely need to manage several asynchronous operations at various levels of concurrency. A common pitfall that is easy to fall into is nesting callbacks, which makes code more difficult to read the deeper the callbacks are nested.
This rule enforces a maximum depth that callbacks can be nested to increase code clarity.
Rationale: The nested callback anti-pattern exposed by creating Promises inside Promises hampers both readability and maintainability. In addition, nested callbacks obscure the traceability of a program's control flow. This rule encourages better stylistic practice like Promise chaining, and frees up horizontal screen real estate by decreasing indentation.
max-statements-per-line
A line of code containing too many statements can be difficult to read. Code is generally read from the top down, especially when scanning, so limiting the number of statements allowed on a single line can be very beneficial for readability and maintainability.
This rule enforces a maximum number of statements allowed per line.
Rationale: This lint rule discourages cramming too much different behaviour onto a single line, or taking the "quick fix" approach to dealing with a line length lint rule by making short methods names so they can be compacted onto one line. Descriptive names and readable lines are important and shouldn't be sacrificed for compactness.
Additionally, there are two minor stylistic rule additions:
▪ lines-between-class-members:always
▪ brace-style:1tbs
GETTING STARTED
There is no best way to get started, but you can consider each of these in turn. Some possible options that could be pursued in any order (or skipped entirely):
▪ Start by looking at the data file we have provided and understanding what kind of data you will be analyzing and manipulating. It is crucial to understand that index.htm and the other files have different structures. You will need to extract different, though complementary information, from each one of them.
▪ Ignoring the rest of the dataset parsing, consider writing a method to get a buildings' address along with tests for this helper method.
▪ Ignoring the provided data, create a fake dataset with few entries. Write the portion of the system that would perform the GROUP and APPLY operations on this small dataset.
Trying to keep all of the requirements in mind at once can be overwhelming. Tackling a single task that you can accomplish in an hour is going to be much more effective than worrying about the whole specification at once. Iteratively growing your project from small task to small task is going to be the best way to make forward progress.
CONTRIBUTION STATEMENT
A survey will be required to detail your contribution to your group's project. This will involve a mandatory survey. Failure to submit the survey by the final deadline will result in a grade of 0 for the checkpoint (for the individual who did not submit it, not the whole group).
ASSESSMENT
Please refer to the grading page for more information
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