Postgraduate: recent fragmented notes

Postgraduate/COMP6214 Open Data Innovation/2021-02-05-licensing-web-of-data-open-data-discovery.md

@@ -0,0 +1,16 @@
+# Licensing, Web of Data, and Open Data Discovery
+
+## 10 Open Data Principles
+
+1. Completeness (including metadata)
+2. ...
+3. Timeliness: release asap
+4. Ease of physical and electronic access
+5. Machine readability
+6. Non-discrimination
+7. Commonly owned or open standards
+8. Licensing
+9. Permanence
+10. Usage costs
+
+## Open Data Licensing

Postgraduate/COMP6214 Open Data Innovation/2021-02-05-structures.md

@@ -0,0 +1,22 @@
+# Open, Closed, Hybrid, and Open Data
+
+> Open Data means **anyone** can **freely access, use, modify, and share** for **any purpose** (subject, at most, to requirements that preserve provenance and openness).
+
+- Closed data requires permissions in order to access, use, modify, and share.
+- Hybrid data is a limited presentation (open) to the proprietary data (closed). (?)
+
+**Linked Data** refers to a set of _best practices_ for publishing and interlinking structured data on the Web.
+
+- Open data is a campaign
+- Linked Data can be appled to open, closed, or hybrid data.
+- _Best practices:_
+  - URIs are used as names for things
+  - HTTP URIs are used so that people can look up the names
+  - RDF, SPARQL are used to query information
+  - Other URIs are included for discovering more things
+
+## Structures of Data
+
+- Tabular
+- Hierarchical
+- Network (Graph)

Postgraduate/COMP6214 Open Data Innovation/2021-02-08-data-cleaning.md

@@ -0,0 +1,42 @@
+# Data Cleaning
+
+Data Cleaning is the process of starting with (semi-)raw data from one or more sources and maintain reliable quality for your applications.
+
+Real-life data are often:
+
+- Incomplete
+- Inconsistent
+- Out-of-context
+- ...
+
+It's important to keep a note of the changes while cleaning the data.
+
+## Types of Error in Real-Life Data
+
+- Syntactic: violation of domain constraints
+- Semantic: discrepancies between values and the real one in real life
+
+## Properties of Clean Data
+
+### Information Completeness
+
+- Closed World Assumption (CWA): assuming the database has all real-world entities except some missing ones
+- Open World Assumption (OWA): assuming the database misses related entities too
+
+### Data Currency
+
+Timeliness; not out-of-date.
+
+## Data Validation
+
+- Consumers understand the data easier
+- Programmers do less "defensive programming"
+- Producers can precisely define and validate the output
+
+## Tools
+
+- Linter: CSVLint, JSONLint
+  - for syntactic errors
+- _OpenRefine_
+- _Excel_, or other spreadsheets
+- _Bespoke Scripts_

Postgraduate/COMP6214 Open Data Innovation/2021-02-12-ontology-and-data-modelling.md

@@ -0,0 +1,9 @@
+# Ontology and Data Modelling
+
+Ontology is a model representing some subject matter or a domain.
+
+## Creating Your Own Ontology
+
+- Start with your own domain
+- Generalise things
+- Find relationships

Postgraduate/ELEC6234 Embedded Processors/2021-02-10-mips.md

@@ -0,0 +1 @@
+# The MIPS Architecture

Postgraduate/ELEC6242 Cryptography/2021-02-07-classic-ciphers.md

@@ -0,0 +1,31 @@
+# Classic Ciphers
+
+Terminologies:
+
+- **Plaintext**: message in a "clear" form
+- **Steganography**: message whose **existence is concealed (hidden)**
+- **Cryptography**: messge in plain view, but the **meaning is concealed (hidden)**.
+- **Cipher**: the operation on groups of **characters**
+
+## Compression & Encryption
+
+Compression and encryption are both about manipulating information (not data or wisdom).
+
+- _Compression_ extracts information from the data to encode it as efficiently as possible.
+- _Encryption_ diffuse a **key** into information as much as possible, and encode it.
+
+## The Best Approach
+
+The best way to practically transmit secure data safely is to:
+
+1. Compress the data
+  - this **removes redundancy** in the plaintext
+  - this also makes encryption (which is slow) **faster**
+2. Encrypt
+3. Add error detection and recovery
+
+## Basic Cryptanalysis
+
+- Frequency analysis
+- "Crib": a known sequence of letters or words, e.g. _q is almost always followed by u_
+- Make guesses