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Re: [ddlm-group] DDLm aliases (subject changed). .. .. .. .. .
- To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
- Subject: Re: [ddlm-group] DDLm aliases (subject changed). .. .. .. .. .
- From: "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com>
- Date: Mon, 31 Jan 2011 13:25:28 -0500 (EST)
- In-Reply-To: <4D46EC21.40606@mcmaster.ca>
- References: <AANLkTi=ATdNovWFiecEwDrbtMdTwZ7guvYuBCGrdnb-i@mail.gmail.com><8F77913624F7524AACD2A92EAF3BFA54166D7D1EDE@SJMEMXMBS11.stjude.sjcrh.local> <4D404DAA.8070804@mcmaster.ca><a06240802c96600c48956@[192.168.2.102]><8F77913624F7524AACD2A92EAF3BFA54166D7D1EE1@SJMEMXMBS11.stjude.sjcrh.local> <a06240800c9668e1faa7c@[192.168.2.102]><8F77913624F7524AACD2A92EAF3BFA54166D7D1EE8@SJMEMXMBS11.stjude.sjcrh.local> <a06240802c9674292646e@[192.168.2.102]><8F77913624F7524AACD2A92EAF3BFA54166D7D1EEB@SJMEMXMBS11.stjude.sjcrh.local> <4D41C6E7.2040109@rcsb.rutgers.edu><8F77913624F7524AACD2A92EAF3BFA54166D7D1EEF@SJMEMXMBS11.stjude.sjcrh.local> <a06240800c967b204830b@[192.168.2.102]><4D46EC21.40606@mcmaster.ca>
Dear Colleagues, There are two very distinct sets of issues in David's message: 1. The management of specification changes in the DDLm dictionary; and 2. The issues of the particular change being considered here. Let me address only the first issue here: the management of specification changes in the DDLm dictionary. Both John B. and David seem uncomfortable with the idea of deprecation rather than abrupt removal of a feature or definition. I refer you to the wikipedia article on deprecation at http://en.wikipedia.org/wiki/Deprecation and quote the first paragraph: "In computer software or authoring programs standards and documentation, the term deprecation is applied to software features that are superseded and should be avoided. Although deprecated features remain in the current version, their use may raise warning messages recommending alternative practices, and deprecation may indicate that the feature will be removed in the future. Features are deprecatedrather than being removedin order to provide backward compatibility and give programmers who have used the feature time to bring their code into compliance with the new standard." In standards work, the approach has changed over time. At the time of Fortran 77, ANSI did not permit deprecation, only removal of a feature. Now ANSI not only permits deprecation, must, at least for software standards, it is the norm for the reasons stated in the wikipedia. Thus the real question is whether there is enough invested in the items being removed to justify retaining them for a while in deprecated form. We have no way of knowing. DDLm has been posted on the IUCr web site since 2007. We have no way of knowing who has seen it and started code development based on it. The prudent thing to do, whether we deprecate or remove, or add a feature is to call attention to the change. We can and should do that in separate change documents, but it also helps to put the warning directly in the DDLm dictionary itself. If we simply remove a deprecated item, we lose a very convenient place to put that notice. There is also the issue of never duplicating tags. Especially while DDLm is in this developmental state, there is the risk, if we remove a tag completely, that we will reintroduce it later with the same name, but a different meaning -- causing unnecessry confusion. So, what I suggest is that we follow the following discipline: 1. If we are removing an item, that we retain that item in the dictionary for at least 5 years with one of the following notations: ***DEPRECATED ITEM DO NOT USE RETAINED FOR REFERENCE ONLY*** ***DEPRECATED ITEM DO NOT USE FOR NEW DEVELOPMENT WORK RETAINED ONLY TO SUPPORT EXISTING CODE AND DATA**** 2. That all deprecated items be gathered into a segregated section of any relevant dictionary. 3. When a deprecated item is finally removed from a dictionary, that a record be kept in a separate deprecated items dictionary to ensure against reuse of the deprecated tag with a conflicting meaning. Regards, Herbert ===================================================== Herbert J. Bernstein, Professor of Computer Science Dowling College, Kramer Science Center, KSC 121 Idle Hour Blvd, Oakdale, NY, 11769 +1-631-244-3035 yaya@dowling.edu ===================================================== On Mon, 31 Jan 2011, David Brown wrote: > Not having done any programming for many years and not being familiar with > the current jargon, I find keeping up with the rapid-fire discussion on > _aliases requires some effort on my part and the discussion has usually > move on before I havc a chance to comment. > > However, being incommunicado on weekends, I took Herbert's draft home where > I could sit down without distraction and see what eactly what was > proposed. The errors and ambiguities in the draft did not help me get my > heasd around the proposal, but I made some progress, and here are my > comments. First the general comments, then particular comments interleaved > in the draft. > > 1. _identifier_set: What does this set identify? The _id seems to flag > arbitrary groups aliases. 'alias_set' would be a better name for this > category, or even just 'set'. What's in a name? It sets certain switches > in the brain, and if these are misset by the dataname, it may take a lot of > work to get them reset. Not conducive to instant communication. > > 2. Why do we need both _alias and _alias_identifier_set categories? They > have indentical information (if the datanames (Syd's word) or tags > (Herbert's word) are any indication). I suppose (though this is no where > spelled out) that _identifier_set would have its own save frame in the > dictionary and would not be an attfibute of a datanmae. If this is a > correct interpretation it would provide a place whare all the alias > datanames in the dictionary could be listed within a single loop). This > seems redundant, but I cannot speak from programming experience. If > alias_identifier_set does not appesr in its own save_ frame, how does it > differ from 'alias'? > > 3. If my supposition in 2. is correct, we would appear to have a problem. > We will now have a variety of flavours of CIF dictionaries, each expressing > a particular programmer's preferences for grouping the aliases. This will > make no difference to the CIFs themselves as these groupings are irrelevant > once a CIF has been written, but if, for example, I am given a program > written by Herbert and different program written by either of the Johns, I > might need a different mmCIF dictionary for each of these two programs, > dictionaries that differ only in the way the aliases are gouped. When I > load my CIF it cannot give instructions on which dictionary to call up > because is will have no knowledge of the idiosyncrasies of the program I > have chosen to use. A possible solution would be to use the _import > feature to create a virtual dictioanry at run time. Thus the > _identifier_set information would be held in a local dictionary that would > be imported into the authorised CIF dictioanry at run time. However, there > are limitations on what can be imported. The _identifier_set category > could be imported but it would be impossible to import the > _identifier_set_id into the alias loop by this mechanism. Since I am not > sure that I understand how Herbert intends to use this feature, I do not > feel competent to suggest a way in which this problem could be handled. > Having programs that used different dialects of CIF dictionaries does not > seem to be in line with the traditional development of CIF, particularly > for a feature that is unlikely to be much used, even if they do not affect > the CIFs themselves. We should think carefully about the implications of > this move. > > 4. My detailed comments follow the feature they comment on below: > > > > save_definition.xref_code > _definition.id '_definition.xref_code' > _definition.update 2011-01-26 > _definition.class Attribute > _description.text > ; > Code identifying the equivalent definition in the dictionary > referenced by the DICTIONARY_XREF attributes. > > Use of _definition.xref_code is deprecated in favor of > use of _alias.xref_code > ; > _name.category_id definition > _name.object_id xref_code > _type.purpose Identify > _type.container Single > _type.contents Code > save_ > > > This item is deprecated. It should be deleted. The alias and xref > iitems have never been tested and it is clear from the current DDLm that > thay are placeholders that are awaiting development. If there are any > programs that make use of the items they can only have been written by > members of this group. The current xref defintiions inadequate and > unworkable. .The is no excuse for leaving this item in if we don't need it. > > save_ALIAS > > _definition.id alias > _definition.scope Category > _definition.class List > _definition.update 2011-01-26 > _description.text > ; > The attributes used to specify the aliased names of definitions. > Every tag has an implicit alias to itself with a null > _alias.xref_code to allow use of the primary tag in > the ALIAS_IDENTIFIER_SET category. > > The use of _alias.identifier_set_id in the key of > this catgeory is provide a placeholder for the > to conform the key of the parent ALIAS category > to the key of the child ALIAS_IDENTIFIER_SET > for automatic joins. It is not intended that > _alias.identifier_set_id should be used in the > ALIAS category when no join is being done. > > > This last paragraph would be easier to undestand if all the words were > present and the sentences grammatical.. In any case it should appear under > _alias,identifierr_set, not here. If I am right in thinking alias is an > attribute and alias_identifier_set is not, how does one join a > non-attribute to an attribute? > > > ; > _category.parent_id ddl_attr > _category_key.primitive ['_alias.definition_id', > '_alias.xref_code', > '_alias.identifier_set_id'] > save_ > > > save_alias.definition_id > _definition.id '_alias.definition_id' > _definition.class Attribute > _definition.update 2006-11-16 > _description.text > ; > Identifier tag of an aliased definition. > ; > _name.category_id alias > _name.object_id definition_id > _type.purpose Key > _type.container Single > _type.contents Tag > save_ > > save_alias.deprecated > _definition.id '_alias.deprecated' > _definition.class Attribute > _definition.update 2006-11-16 > _description.text > ; > Specifies whether use of the alias is deprecated > ; > _name.category_id alias > _name.object_id definition_id > > > .object_id should be the second part of the _definition.id, i.e., > 'deprecated'. This needs correcting in many places. > > _type.purpose STATE > _type.container Single > _type.contents YesorNo > _enumeration.default No > save_ > > > save_alias.dictionary_uri > _definition.id '_alias.dictionary_uri' > _definition.update 2011-01-26 > _definition.class Attribute > _description.text > ; > Dictionary URI in which the aliased definition belongs. > _alias.dictionary_uri is deprecated in favor if > _alias.xref_code > ; > _name.category_id alias > _name.object_id dictionary_uri > _type.purpose Identify > _type.container Single > _type.contents Uri > save_ > > > This item should be moved to the _dictionary_xref category. The xref.id > is sufficient link. Again, the fact that it may appear in the draft > dictionaries should not prevent it being deleted in DDLm since the draft > dictionaries are just drafts and will be chaniged once we have sorted out > how to do the aliases. > > > save_alias.identifier_set_id > _definition.id '_alias.identifier_set.id' > _definition.class Attribute > _definition.update 2011-01-26 > _description.text > ; > A code identifying an identifier_set of related tags. > This linked item is provided in the ALIAS category to > ensure that the key of the ALIAS category is > conformed to the key of the ALIAS_IDENTIFIER_SET > category. The alias has not been joined with > ALIAS_IDENTIFIER_SET, _alias.identifier_set_id > it is not intended that _alias.identifier_set_id > in the ALIAS category. > > > I cannot make much sense of the last sentence. Perhaps there are missing > words? > > > This is a pointer to _identifier_set.id > ; > _name.category_id alias > _name.object_id code > > > See above. 'code' is not the proper .object_id > > _name.linked_item_id '_identifier_set.id' > _type.purpose Key > _type.container Single > _type.contents Code > _enumeration.default . > save_ > > > save_alias.xref_code > _definition.id '_alias.xref_code' > _definition.update 2011-01-26 > _definition.class Attribute > _description.text > ; > Code identifying the dictionary containing the primary > definition of the dictionary as given in the > DICTIONARY_XREF category. > > ; > _name.category_id definition > _name.object_id xref_code > _name.linked_item_id '_dictionary_xref.code' > _type.purpose Key > _type.container Single > _type.contents Code > save_ > > > save_IDENTIFIER_SET > > _definition.id identifier_set > _definition.scope Category > _definition.class List > _definition.update 2011-01-27 > ; > Data items used to describe the identifier_set identifiers > used in this dictionary. Data items in this category > are NOT used directly as attributes of individual data items. > See linked item _alias_identifier_set.identifier_set_id > for such uses. > > > ; > _category.parent_id ddl_attr > _category_key.generic '_identifier_set.id' > > save_ > > save_identifier_set.id > _definition.id '_identifier_set.id' > _definition.class Attribute > _definition.update 2011-01-27 > _description.text > ; > A code identifying an identifier_set of related tags. > The coverage of an identfier_set may conform precisely > to the set of tags in a particular dictionary, > or to tags drawn from multiple dictionaries or > to a subset of tags from a single dictionary. > > The same tag may belong to multiple identifier > sets, and a given tag may not belong to any > identifier set, in which case the only associated > identifier set is a null value. > > > Presumably the second line should read 'need not belong to any'. The > wording above is ambiguous. > The last line should read 'identifier set id' and its default value should > be given explicitly. What is nul? > Possible nul values are 'nul', '0', ' ', '?', '.', etc. > > To help ensure that dictionaries can be merged, > each code should either begin with an IUCr-registered > prefix or, if not prefixed, have been approved > by COMCIFS. The special prefix 'local_' may be > use for purely internal purposes of an organization. > > > I assume these are not datanames that appear in the dictionaries but a list > of COMCIFS enumerations, some of which might appear in a non-exclusive > enumeration list. What happens if someone chooses 'joeblow' as an id? > > ; > _name.category_id identifier_set > _name.object_id code > _type.purpose Key > _type.container Single > _type.contents Code > > save_ > > save_identifier_set.description > _definition.id '_identifier_set.description' > _definition.class Attribute > _definition.update 2011-01-27 > _description.text > ; > A description of the identifier_set > ; > _name.category_id identifier_set > _name.object_id code > _type.purpose Describe > _type.container Single > _type.contents Text > > > save_ > > save_ALIAS_IDENTIFIER_SET > > _definition.id alias_identifier_set > _definition.scope Category > _definition.class List > _definition.update 2011-01-27 > ; > The attributes used to specify the identifier_set of > tags to which a given tag belong. > > A given tag may belong to multiple identifier_sets > and may be cited against multiple dictionaries. > > Note that _alias_identifier_set.identifier_set_id is a > component of the key of ALIAS_IDENTIFIER_SET. If the > denormalized join presentation is used to bring the object > ids of this child category up into the parent > ALIAS category, then _alias.identifier_set_id will > we used as an implicit addition to the key of > the denormalized ALIAS category. > > Until DDLm can be formally revised to automatically > handle the necessary promotion of child catgeory keys > in denormalized joins, a place-holder > _alias.identifier_set_id has been defined in the > ALIAS catgeory. > > ; > _category.parent_id alias > _category.parent_join Yes > _category_key.primitive ['_alias_identifier_set.identifier_set_id', > '_alias_identifier_set.definition_id', > '_alias_identifier_set.xref_code'] > save_ > > save_alias_identifier_set.definition_id > _definition.id '_alias_identifier_set.definition_id' > _definition.class Attribute > _definition.update 2011-01-27 > _description.text > ; > Together with _alias_identifier_set.xref_code, identifies > an alias belonging to an identifier_set. An alias may > belong to any number of identifier_sets, including zero. > > ; > _name.category_id alias_identifier_set > _name.object_id definition_id > _name.linked_item_id '_alias.definition_id' > _type.purpose Key > _type.container Single > _type.contents Tag > save_ > > save_alias_identifier_set.identifier_set_id > _definition.id '_alias_identifier_set.identifier_set_id' > _definition.class Attribute > _definition.update 2011-01-27 > _description.text > ; > Identifies an identifier_set to which the alias > identified by _alias_identifier_set.definition_id > and _alias_identifier_set.xref_code ) belongs. > > A pointer to _identifier_set.id > ; > _name.category_id alias_identifier_set > _name.object_id code > _name.linked_item_id '_identifier_set.id' > _type.purpose Key > _type.container Single > _type.contents Code > > save_ > > > save_alias_identifier_set.xref_code > _definition.id '_alias_identifier_set.xref_code' > _definition.class Attribute > _definition.update 2011-01-21 > _description.text > ; > A code identifying the actual dictionary, > virtual dictionary or other logical grouping > to which the identifier tag belongs. > > > What is this identifier tag - '.definiton_id' or '.definiton_set_id'? > > ; > _name.category_id alias_identifier_set > _name.object_id code > _name.linked_item_id '_dictionary_xref.code' > _type.purpose Key > _type.container Single > _type.contents Code > save_ > > > > > We also need to refined the _dictionary_xref category. '.uri; should be > added, '.format' should be better derfined or deleted. Perhaps '.version' > should also be added. Definining the dictionaries is just as important as > definiting the definition_sets > > David > >
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