A small question

[Michael Sobolev <mss@transas.com>]

Hello,

I've got a small question: where all these entities come from? :)

Well, what actually I am trying to find out is why certain things are different
in different files.  To begin with, let's have a look on /usr/lib/sgml/catalog
file:

PUBLIC "ISO 8879:1986//ENTITIES Added Latin 1//EN//HTML" entities/ISOlat1
PUBLIC "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML" entities/ISOlat1 -- incorrect, deprecated --
PUBLIC "ISO 8879:1986//ENTITIES Added Latin 1//EN"       entities/ISOlat1
PUBLIC "ISO 8879-1986//ENTITIES Added Latin 1//EN"       entities/ISOlat1 -- incorrect, deprecated --

These make me think that it does not matter whether //HTML suffix is there the
entities are the same.  OK, let's have a look on entities/ISOlat1 file:

<!-- Character entity set. Typical invocation:
     <!ENTITY % ISOlat1 PUBLIC
       "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
     %ISOlat1;
-->

This time I see that the file is for HTML-specific entities.  Moreover,
earlier in the file I see:

     This has been extended for use with HTML to cover the full
     set of codes in the range 160-255 decimal.

Occasionally I found yet another file iso-entities-8879.1986/ISOlat1 which
has a simple notice:

<!-- Character entity set. Typical invocation:
     <!ENTITY % ISOlat1 PUBLIC
       "ISO 8879:1986//ENTITIES Added Latin 1//EN">
     %ISOlat1;
-->

Aha, at least, this makes me think that these two files are different!  They
are defining different sets of entities.  BUT, according to
/usr/lib/sgml/catalog file, the first set of entities can be also referred to
as to "...//EN".

So here is my question, how I should treat all this ifnormation?

My main concern (well, it's where this investigatation started from) is entity
named copy.  If I look into first file I see

    <!ENTITY copy CDATA "&#169;">

I see no definition for copy in the second file, while iso-.../ISOnum file
defines:

    <!ENTITY copy   SDATA "[copy  ]"--=copyright sign-->

These are different definitions and while in the second case I could process
this SDATA [copy  ] for producing &copy; in HTML output and \copyright in TeX
output, I lack this possibility in first case.

Please comment.

Thanks,

--
Mike

PS  I may have confused using `a' and `the' in some case as Russian lacks this
    notion. :)