日本における貧困率（相対的貧困）と世界貧困線（絶対的貧困）

日本における貧困率のカウントには、相対的貧困が用いられる。日本における貧困率にカウントされるのは、2017年の国民生活基礎調査の場合、年間の等価処分所得が122万円未満の世帯。
世界における貧困率のカウントには、絶対的貧困が用いられる。世界単位で貧困率にカウントされるのは、2015年の世界銀行の設定の場合、貧困線を購買力平価が1.90$/日（1ドル112円として年間で7.77万円）未満の世帯。

iOS 11ではリマインダーに保存したツイートのURLからTwitterのアプリを開けない

• iOS 10.3では、リマインダーに保存したツイートのURLはTwitterのアイコンで表示される。また、TwitterのアイコンをタップするとTwitterのアプリが起動し、対応するツイートが表示される。
• iOS 11.0では、リマインダーに保存したツイートのURLはアイコンなしで表示される（Safariのアイコンも表示されない）。また、Twitterのアイコンをタップしても、TwitterのアプリもSafariも起動しない。なお、ツイートのURLでない一般サイトのURLにはSafariのアイコンが表示される。

今のところ回避方法は見つかっていない。

A List of What Cannot JCache do

• JCache cannot save the order of insertion. You should use LinkedHashMap for that purposes.
• JCache cannot update whole entries in a cache atomically. You should use AtomicReference or some locking mechanisms for that purpose. (Ofcourse you can update a cache atomically if a cache has always only one reference.)
• JCache doesn't offer read-write lock. You should use ReadWriteLock for that purpose.
• JCache doesn't offer unmodifiable view of cache. You should use Collections.unmodifiableMap() for that purpose.

The meanings of word "cache" in software engineering

I think the word "cache" has so many different meanings in different contexts like below.

Note: In this list, the word "invalidated" means the source of cached value might be changed.

1. Something like the cache in web browsers. The cache stores the result of each operation that had already called (Typically, these operations had cost large resources). The values in the cache might be invalidated partially because some input is volatile, but not coherent.
2. Something like the result of precomputation. The cache stores the result of operations that programmers specified (because it will cost large time or memory). It might not be invalidated.
3. Something like memoization. The cache stores the result of each operation that the programmers specified and had already called. It might not be invalidated but might be discarded because of time-space tradeoff (e.g. weak reference in Java). It should be coherent.
4. Something like the in-memory views in RDBMS. The cache stores the values in files or tables that programmers specified, in order to reduce the cost of access or implement read-only view. It might be invalidated and must be coherent. It must be updated atomically.
5. Something like on-memory copy of files. The cache stores the values in files or tables that programmers specified, in order to reduce the cost of access. Sometimes it might be invalidated, but the programmers can control the timing of invalidation. The coherency doesn't matter, but it must be updated atomically.
6. Something like cache on CPUs or L2ARC. The cache stores the data that had already accessed, in order to reduce the cost of access. It might be updated or invalidated. It must be coherent, but doesn't have to be updated atomically.
7. (Not in the table below) Something like on-memory data stores (e.g. memcached). The cache stores the values that programmers specified. It might be updated and never be invalidated (sometimes values are only in the cache!). It doesn't have to be updated atomically.

I tried to organize these concepts in a table like below:

	Target of Cache	Invalidated?	Coherent?	Atomic?	Example
1	each	no	no	no	Memoization
2	each	no	no	yes	Memoization
3	each	no	yes	no	Memoization
4	each	no	yes	yes	Memoization
5	each	yes	no	no	Cache in Web Browsers
6	each	yes	no	yes	Cache in Web Browsers
7	each	yes	yes	no	?
8	each	yes	yes	yes	?
9	whole	no	no	no	Precomputation
10	whole	no	no	yes	Precomputation
11	whole	no	yes	no	Precomputation
12	whole	no	yes	yes	Precomputation
13	whole	yes	no	no	?
14	whole	yes	no	yes	On-memory Copy of Files
15	whole	yes	yes	no	CPU Cache or L2ARC
16	whole	yes	yes	yes	In-memory Views in RDBMS

Difference of GitHub API and GitLab API

Format of Personal Access Tokens

• In GitHub, personal access tokens are hex string, like e72e16c7e42f292c6912e7710c838347ae178b4a.
• In GitLab, personal access tokens are like Base62 string, like 9koXpg98eAheJpvBs5tK.

Personal Access Tokens as OAuth2 Tokens

• In GitHub, personal access tokens are used as OAuth2 tokens.
• In GitHub, personal access tokens are different from OAuth2 tokens (There are also private tokens, but I couldn't find the way to get it).

HTTP Request Header for Authorization

• In GitHub, personal access tokens are passed via "Authorization" header in HTTP request like Authorization: token e72e16c7e42f292c6912e7710c838347ae178b4a (also you can use Authorization: Bearer instead of Authorization: token).
• In GitHub, personal access tokens are passed via "PRIVATE-TOKEN" header in HTTP request like PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK.

Query String for Authorization

• In GitHub, you can pass personal access tokens via query string like GET /projects?access_token=e72e16c7e42f292c6912e7710c838347ae178b4a.
• In GitLab, you can pass personal access tokens via query string like GET /projects?private_token=9koXpg98eAheJpvBs5tK.

HTTP Status Code for Authorization Failure

• In GitHub, you will get 404 error when you failed to authorize (you cannot distinguish the authorization error from the other errors).
• In GitLab, you will get 401 error when you failed to authorize (you can distinguish the authorization error from the other errors).

How to Specify a Project

• In GitHub, you can specify a project by name, like GET /api/v3/repos/Project/Repository/pulls.
• In GitLab, you cannot specify a project by name. You should use a project ID, like GET /api/v4/projects/12/merge_requests. You cannot see the project ID in the Web UI (You have to call API for project IDs, or see hidden tag in HTML source).

How to List All Comments in Pull Requests

• In GitHub, you can list all the comments in pull requests like GET /api/v3/repos/Project/Repository/pulls/comments.
• In GitLab, you cannot list all the comments in pull requests. You should specify each merge request and get comments like GET /api/v4/projects/12/merge_requests/42/notes (42 is the iid of a merge request).

Content-Type header in HTTP response

• HTTP response of GitHub API contains Content-Type header like Content-Type: application/json; charset=utf-8.
• HTTP response of GitLab API does not contain Content-Type header, So Invoke-RestMethod of PowerShell causes mojibake (see http://satob.hatenablog.com/entry/2018/01/18/014615).