Replace 'event' with 'tag' in explainer

It was suggested to change the term 'event' to 'tag' to reference the
section name and the entries within the section. The suggested reasons
were they can be used something other than events in future, and the
term event can be confusing with other concepts on the web.

Closes WebAssembly#159.

Author: aheejin

proposals/exception-handling/Exceptions.md

@@ -45,12 +45,12 @@ instruction. Thrown exceptions are handled as follows:
 1. If the call stack is exhausted without any enclosing try blocks, the embedder
    defines how to handle the uncaught exception.
 
-### Event handling
+### Exception handling
 
 This proposal adds exception handling to WebAssembly. Part of this proposal is
 to define a new section to declare exceptions. However, rather than limiting
 this new section to just defining exceptions, it defines a more general format
-that allows the declaration of other forms of events.
+that allows the declaration of other forms of events in future.
 
 In general, an event handler allows one to process an event generated by a block
 of code. Events suspend the current execution and look for a corresponding event
@@ -62,22 +62,21 @@ Exceptions are a special case of an event in that they never resume. Similarly,
 a `throw` instruction is the suspending event of an exception. The catch block
 associated with a try block defines how to handle the throw.
 
-WebAssembly events (i.e. exceptions) are defined by a new `event` section of a
-WebAssembly module. The event section is a list of declared events associated
-with the module.
+WebAssembly exceptions tags are defined in a new `tag` section of a WebAssembly
+module. The tag section is a list of declared tags associated with the module.
 
-Each event has an `attribute` and a `type`. Currently, the attribute can only
-specify that the event is an exception. In the future, additional attribute
+Each tag has an `attribute` and a `type`. Currently, the attribute can only
+specify that the tag is for an exception. In the future, additional attribute
 values may be added when other events are added to WebAssembly.
 
 To allow for such a future extension possibility, we reserve a byte in the
 binary format of an exception definition, set to 0 to denote an exception
-attribute, but for the moment we won't use the term event in the formal spec.
+attribute.
 
 ### Exceptions
 
 An `exception` is an internal construct in WebAssembly. WebAssembly exceptions
-are defined in the event and import sections of a module.
+are defined in the tag and import sections of a module.
 
 The type of an exception is denoted by an index to a function signature defined
 in the `type` section. The parameters of the function signature define the list
@@ -418,28 +417,21 @@ Each exception type has the fields:
 A single-byte unsigned integer indicating the kind of definition being imported
 or defined:
 
-* `0` indicating a `Function` [import](Modules.md#imports) or
-[definition](Modules.md#function-and-code-sections)
-* `1` indicating a `Table` [import](Modules.md#imports) or
-[definition](Modules.md#table-section)
-* `2` indicating a `Memory` [import](Modules.md#imports) or
-[definition](Modules.md#linear-memory-section)
-* `3` indicating a `Global` [import](Modules.md#imports) or
-[definition](Modules.md#global-section)
-* `4` indicating an `Event` [import](#import-section) or
-[definition](#event-section)
+* `4` indicating a `Tag`
+[import](https://github.com/WebAssembly/design/blob/main/BinaryEncoding.md#import-section) or
+[definition](#tag-section)
 
 ### Module structure
 
 #### High-level structure
 
-A new `event` section is introduced and is named `event`. If included, it must
-appear immediately after the memory section.
+A new `tag` section is introduced. If included, it must appear immediately after
+the memory section.
 
-##### Exception section
+##### Tag section
 
-The `event` section is the named section 'exception'. For ease of validation,
-this section comes after the [memory
+The `tag` section is the named section 'tag'. For ease of validation, this
+section comes after the [memory
 section](https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md#memory-section)
 and before the [global
 section](https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md#global-section).
@@ -452,42 +444,42 @@ So the list of all sections will be:
 | Function | `3` | Function declarations |
 | Table | `4` | Indirect function table and other tables |
 | Memory | `5` | Memory attributes |
-| Event | `13` | Event declarations |
+| Tag | `13` | Tag declarations |
 | Global | `6` | Global declarations |
 | Export | `7` | Exports |
 | Start | `8` | Start function declaration |
 | Element | `9` | Elements section |
 | Code | `10` | Function bodies (code) |
 | Data | `11` | Data segments |
 
-The event section declares a list of event types as follows:
+The tag section declares a list of tag types as follows:
 
 | Field | Type | Description |
 |-------|------|-------------|
-| count | `varuint32` | count of the number of event to follow |
-| type | `event_type*` | The definitions of the event types |
+| count | `varuint32` | count of the number of tags to follow |
+| type | `tag_type*` | The definitions of the tag types |
 
 ##### Import section
 
 The import section is extended to include exception definitions by extending an
 `import_entry` as follows:
 
-If the `kind` is `Event`:
+If the `kind` is `Tag`:
 
 | Field | Type | Description |
 |-------|------|-------------|
-| `type` | `event_type` | the event being imported |
+| `type` | `tag_type` | the tag being imported |
 
 ##### Export section
 
 The export section is extended to reference exception types by extending an
 `export_entry` as follows:
 
-If the `kind` is `Event`:
+If the `kind` is `Tag`:
 
 | Field | Type | Description |
 |-------|------|-------------|
-| `index` | `varuint32` | the index into the corresponding event index space |
+| `index` | `varuint32` | the index into the corresponding exception index space |
 
 ##### Name section
 
@@ -498,12 +490,12 @@ follows:
 | --------- | ---- | ----------- |
 | [Function](#function-names) | `1` | Assigns names to functions |
 | [Local](#local-names) | `2` | Assigns names to locals in functions |
-| [Event](#event-names) | `3` | Assigns names to event types |
+| [Tag](#tag-names) | `3` | Assigns names to tag types |
 
-###### Event names
+###### Tag names
 
-The event names subsection is a `name_map` which assigns names to a subset of
-the exception indices (Used for both imports and module-defined).
+The tag names subsection is a `name_map` which assigns names to a subset of
+the tag indices (Used for both imports and module-defined).
 
 ### Control flow operators