# Makumba Specification

OLDSTYLE features that are still accepted are presented in darkblue
(INTENDED features are presented in red with parentheses)

This is a note for users
This is a note about makumba internals for makumba developers

## Content

- Data Definition Language... writing MDDs
  - Types, objects, databases
  - Fields
  - Default fields
  - Simple field types
    - int - real - char - text - date
  - Structural (relational) types
    - ptr - set
  - Macro types
  - Field attributes
  - Object title
  - Include mechanism
- OQL language ... getting data from the database
- Business Logic ... adding logic to basic operations
  - Attributes
  - Java Handler classes
  - Login, <mak:login>, <mak:logout/>
- Presentation and internal representation principles
- Presentation with JSP taglib ... viewing/editing data thru HTML pages
  - Makumba in Java Server Pages
    - Makumba Controller
    - JSP tag parameters
  - <mak:list>
    - <mak:object>
    - Attributes and OQL in <mak:list > and <mak:object >
    - <mak:value/>
    - mak:count(), mak:maxCount(), mak:lastCount()
    - <mak:if>
    - <mak:attribute>
  - Forms
    - <mak:newForm>
    - <mak:addForm>
    - <mak:editForm>
    - <mak:form>
    - <mak:input> and <mak:option>
    - <mak:action>
  - <mak:deleteLink/>
  - <mak:response/>

## Data Definition Language

(the Makumba abstract level)

### Types, objects, databases

Data definitions describe data types (or classes). They are placed in files contained in directory hierarchies, and the directory name is part of the type name (similar to Java packages). For example the file best/Student.mdd describes the type best.Student. Type names can contain letters, digits, underscores and dashes and cannot contain slashes and dots. Usually, the directories are used to separate organisations and projects.

Current Java implementation finds the data definition files as follows:

- the designated file extension is `.mdd` (Makumba Data Definition)
- relative to CLASSPATH (e.g. `classes/best/Student.mdd`)
- in a directory called "dataDefinitions/" in the CLASSPATH (e.g. `classes/dataDefinitions/best/Student.mdd`)
- OLDSTYLE: if no mdd file is present, the no-extension file (i.e. best/Student) is looked up

Data objects (records) are stored in databases.

The actual implementation of the database is not part of this specification but implementation suggestions will be made. Data can be copied and/or replicated between different databases, even between different DB engine types.

Replication is not yet implemented, but the design is prepared for it. Copying works.

### Fields

Every data definition file contains field definitions, separated by newline.

A field definition looks like:

    fieldname= [attributes] fieldtype [parameters] [; description]

default values are supported internally, but not by the mdd parser
As an implementation guideline, field names tend to stay approximately the same in:

- http requests
- Record instances (java.util.Dictionary in the current Java API)
- database columns
- etc

(Automatic labeling: The field description might be used at interface levels to present that field. It is typically shown at the left of, or somewhere near to, the input control (text box, radio button, chooser, etc) that allows for data input in that field. If a field description is not present, its field name stands for its description by default.)

Comment lines can be inserted in the data definition files as follows:

    # your comment...

### Default fields

Every datatype has some additional fields by default, as follows:

- Primary Key field, consisting of two parts [DBSV with 8 bits | UID with 24 bits]:
  - Database identifier (DBSV). It is unique (within the webapp) per database. All objects created thru that webapp and in that database get the same value. It is set by property dbsv in the database config file.
  - Object identifier (UID): unique id for the object in the given database.
  This combination ensures that no two objects of one type have the same primary key field. See how to configure this.
  The name of the primary key field is the same with the last part of the type name. If another field by that name is defined by the makumba user, this field will be renamed in the database.
- Object creation time
  Can be accessed as TS_create.
- Last modification time. Updates whenever the object is changed. The initicial value is TS_create.
  Can be accessed as TS_modify.

### Simple field types

#### int

A 32-bit integer. For example

    shoeSize= int; Shoe size

If the int can have a limited number of values, it can be described as follows

    gender= int{ "male"=0, "female"=1 }; Sex

This will help the presentation layer to present a suitable input control (e.g.
)

"deprecated" can be used in this way to denote a deprecated option:
userType = int{"type1"=10, "type2"=10,"old"=0 deprecated}
In the present implementation, this type is called "intEnum" internally.
Negative numbers are supported (e.g. int { "aa"=5, "bb"=2, "cc"=-10}).

#### real

A read number with double precision with (2-2-52)·21023 as max value and 2-1074 as min value. For example:

    high= real; high of a person

#### char

A char field contains a number of characters. Maximal width must be specified and is limited to 255. (Optionally a minimal number of characters (lesser than max) can be indicated). Both must be positive integers. For example:

    #fieldName= char[maxWidth]
    name= unique char[80]; Username
    #fieldName= char[minWidth..maxWidth]
    password= encrypted char[6..10]; Secret password

"`unique`" and "`encrypted`" are field attributes, explained below.

Pay close attention to the character set (charset) for encoding the characters. In Java the charset is Unicode, but the JSP/HTML pages have their own encoding settings, as well as the database, etc.

DEPRECATED (use int{...} instead): If the char can have a limited number of value, it can be described as follows

    gender= char{ "male", "female" }; Sex

This will help the presentation layer to present a suitable input control (e.g. a HTML SELECT)

in the present implementation, this type is called "charEnum" internally

#### text

An unlimited-length string of bytes or characters. This type was designed to accomodate large text or binary content. It is implemented with LONGVARBINARY or its counterparts, depending on the underlying DB engine.

    application= text ; Application letter
    description=text  ; Description of object
    image= text	  ; Picture attachment

#### date

A date and/or time.

    birthdate= date; Date of birth
    arrivalTime= date; Arrival time

### Structural (relational) types

#### Pointers (ptr)

Pointers define a reference to an object of a certain type. For example

    citizenship= ptr general.Country; Citizenship

the `ptr` keyword might be ommitted in future parsers

The type can be defined on-the-spot for a single usage. For example

    addres= ptr ; Address
    address->street= char[80]; Street
    address->number= int; Number

The main difference between sets of external types and internal sets is that when the host object (e.g. Person.mdd that has the above field "address") is deleted from the database (DB), also all elements of the set (addresses) are deleted automatically, so there is no orphans (addresses) in the DB. Elements (addresses) of an internal set of some host object (Person X) also can't be used in a set of some other host object (Company Y).
future parsers might read this:

    address= ptr{
        street= char[80]; Street
        number= int; Number}; address

this type is known internally as ptrOne

#### Sets (set, bag, list)

Sets define a number of references to multiple objects of a certain type. For example:

    language= set general.Language; Spoken languages

This type accomodates sets, bags and lists. The set and list constraints (sets have to contain only one element of a certain value and lists have to be ordered) have to be cared for by the programmer. Lists are easy to represent, just having an integer field, for the order.

The type which the set is made of can be defined on the spot:

    addresses= set; Addresses
      addresses->street= char[80]; Street
      addresses-> number= int; Number

the future parser might recognize this form:

    addresses: set{
        street: char[80]; Street
        number: int; Number }; Addresses

this type is known internally as setComplex

The set can contain enumerated int values :

    place= set int {"home"=1, "away"=0} ; Home or away

this is currently known internally as setintEnum

DEPRECATED: The set can contain enumerated char values :

    place= set char {"home", "away"} ; Home or away

It means that place is a set that can take only the "home" and "away" values.
This is currently known internally as setcharEnum

### Macro types

A name can be defined for a more complex type and it can be reused in the file. This can be done with a !type directive

    !type.yesno= int{"yes"=1, "no"=0}
    !type.rank= int{"neutral"=0, "very good"=5, "very bad"=-5}
    married=yesno
    happyInLife=rank

### Field attributes

- fixed fields can only set during the record's insertion in the database. The subsequent updates will not update the field
- not null fields will produce a exception if an attempt is made to insert/update without them being initialized
- unique fields have a unique value in the respective object, for the respective type
- (encrypted fields are encrypted when written to the database and decrypted when read)

Currently only fixed and not null field attributes are working, while support for unique is in progress.

### Object title

The object title is used for set and ptr choosers

One of the fields is always the object title, and is normally presented differently from other fields in user interface. For example, when you have a field that is a set and you use a mak:input on that field, Makumba will automatically create a list with all the items in the set and it will use the object title to know what field to display. The default is the field called "name" if that exists, otherwise it is the first non-pointer field in the record description. If another field needs to be title, it can be specified like

    !title=gender

for the on-the spot types in the current implementation, the following notation works:

    address->!title= street

### Include mechanism

A record description can include text from one or more files. This is declared as

    !include=name_of_included_type

The included file has the idd extension and is found in a similar way like the data definitions.

The included file is inserted instead of the !include line. There can be more include lines in a record description file. If a field is defined that exists also in the included metadata, the defined field takes precedence. If

    fieldname=

it means that it does not actually exist. this can be used to cancel an included field.

include might be replaced by more advanced concepts such as inheritance and type inclusion (rather than reference in foreign table)

## OQL language

The database can be interrogated using the following language ( [] means optional, {} means any number of repetitions). OQL is similar to SQL, a specification can be found at http://www.odmg.org (or check this PDF). Makumba recognizes a subset of OQL at the moment, which it translates to the host SQL when necessary.

    SELECT expression [[AS] label] {, expression [[AS] label] }
    FROM {type [AS] label | label.field{.field} [AS] label }
    [   WHERE expression
        [    GROUP BY expression {,expression}
            [  HAVING expression {,expression}  ]
        ]
    ]
    [ORDER BY expression {,expression} [(ASC|DESC)] ]

Notations like `label.field{.field}` only allow "`field`" to be of pointer type in expression and set type in FROM. In expressions, also `label.ptr{.ptr}.simplefield` is valid.

If a label, representing a type, appears alone in an expression, a default field will be added. The default field depends on the type of the label:

- for set XXX types (sets of foreign objects), the label denotes the pointer to the set member
- for set int { } and set char { } types, the label denotes the set member (i.e. and int or a string)
- for all other types, the label denotes the pointer to that object

In OQL, NULL values are named 'nil', example

    ms.account_active=1 OR ms.account_active=nil

In the future, the MDDs should use 'nil' instead of null, e.g. nickName = not nil char[20]

## Business Logic (BL)

### Attributes

Java Server Pages use attributes to keep the state of the application. Makumba builds upon that its own notion of Attributes that keep the read-only state of a makumba task. They represent the "environment" of that makumba task. The typical example is a JSP page during execution, with its HTTP and session parameters as attributes. Since other kinds of attributes are possible, the attribute specification is kept HTTP-independent. Makumba BL code sees the attributes as an `org.makumba.Attributes` object.

### Java handler classes

Java handler classes are classes that implement the "business logic" of the organisation. Every makumba page will look for a handler, and will call its methods when needed. Check also the <mak:newForm> to know which methods are called. If a handler class exists, then some operations cannot be performed if these methods are not defined in the handler class.

#### Handler Discovery

Each page will determine its handler class on first access, after being compiled. If the class changes on disk, a webapp reload is generally needed for the new class to take effect.

The handler is 'discovered' by decomposing the full path of the JSP page, and finding a class with a matching name. Decomposition breaks the full path at every capital letter, or forward slash. For example, with the page path `/student/mycv/indexPersonal.jsp`, the following criteria are applied, in order:

criterium | Java classes checked for
--- | ---
page name | `StudentMycvIndexPersonalLogic`
caps parts of page/directory name | `StudentMycvIndexLogic`
directory name | `StudentMycvLogic`
parent directory name(s) | `StudentLogic` `Logic`

The class name prefix (e.g. java package name) can be regulated per parts of the site in a file called MakumbaController.properties which can be found in the CLASSPATH (just like MakumbaDatabase.properties). For example, the file can contain:

    /student=org.eu.best
    /makumba=org.makumba
    /=test

path | Java classes checked for
--- | ---
`/student/mycv/index.jsp` | `org.eu.best.MycvIndexLogic` `org.eu.best.MycvLogic` `org.eu.best.Logic`
`/makumba/tests/x.jsp` | `org.makumba.TestsXLogic` `org.makumba.TestsLogic` `org.makumba.Logic`
`/some.jsp` | `test.SomeLogic` `test.Logic`

There are good reasons to take into account the name of the response page of a form when looking for the business logic. Still, it is the name of the page that contains the form which matters not the name of the action page. It is good practice for both pages to actually have the same handler class.

All methods of the handlers are http-independent. Methods are non-static, so the handler classes can use inheritance to their advantage. Still, handler classes are singletons (only one instance of a certain class in a JVM). For example, the validation of a form can be in a class that is closer to the actual JSP application (view level) while the more view-independent methods can be in the parent of that class. For example:

    org.eu.best.minerva.StudentHandler extends org.eu.best.StudentHandler

#### Role of Java handlers

1. find attributes unknown by pages. e.g.

       <mak:object from="best.Student stud" where="stud=$student"> ...</mak:object>

   If the `$student` attribute is not known in the page (from a http argument) or in the session, the `find{AttributeName}(Dictionary existingAttributes, Database d, String expression)` method is called for the Handler object. In this case findStudent(). The handler has to compute the attribute, based on existing attributes, making DB accesses.

   The find{AttributeName} method's name is constructed literally from the name of the attribute (capitalising only the first letter), so dots and other illegal characters for java identifier names, are not to be used. Also, one shouldn't use 2 attribute names that differ only in the capitalisation of the first letter.

   For example "`lbg.$lbg_order`" (in an example elsewhere in the specs), will generate a call `findLbg_order(otherAttributes, db)` and the Java handler will return the default ordering for LBGs (say "name").

   If the attribute is computed successfully, it is associated with the session (i.e. set as JSP attribute in session scope)

   If not, an exception will be thrown (typically `org.makumba.UnauthenticatedException`), and the engine will act accordingly (i.e. ask for authentication).

2. execute action methods in response to makumba forms. See makumba forms and actions below.

3. ( later: return query parts, as methods. e.g. `<mak:value expr="lbg.$title()" />` will generate a call to method `BestInternalLbgTitle(lbg)` which can return an OQL expression "`concat(lbg.id, \"-\" lbg.name)`" (such methods can be put directly in the Makumba data definitions) For now, OQL only accepts count() and sum(), but that can be easily fixed, till then, the method can be replaced by hand: `<mak:value expr="lbg.id"/>-<mak:value expr="lbg.name"/>` )

#### Handler Initialization

Whenever a handler is used in a new context (i.e. with a different set of attributes, e.g. a new page access), a method called `checkAttributes(Attributes a, Database db)` is looked for and executed, if it is defined.

`checkAttributes` can perform sanity checks for attributes used in the respective logic (in case of mismatches, `org.makumba.UnauthorizedException` is usually thrown), can load attributes that are absolutely needed for page execution (formerly given by the requiredAttributes() method), etc.

### Login

Login is done as a result of a missing attribute (possibly invoked in `checkAttributes`), when a `find{AttributeName}` method is called. The missing attribute is the principal that needs to log in.

If the attribute cannot be found due to wrong login information, `org.makumba.UnauthenticatedException` is usually thrown.

The principal (the person who logs in) can have more members (e.g. group, Lbg, Company representatives). E.g. the findCompany() method will check to see if the authentication (email_address and password) corresponds to any company representative of that company. If yes, it will return that company.

Login can be done in 2 ways:

1. (Http basic authentication login: will set the attributes $username, $password )
2. cookie login: done in a page called `login.jsp`, in the same directory or (if missing) in any of the parents. It should contain at least:

       <mak:login>
         <input type=text name=username>
         <input type=password name=password>
         <input type=submit>
       </mak:login>

   The login form will pass further (as hidden arguments) all the http parameters it got. Note that `<mak:login>` is only needed upon automatic login (a page displayed when the user requested another page, that needs authentication). If you wish to ask for login manually in a startup page, a normal HTML form is enough.

To cancel out a certain attribute, in order to produce a new login, the logout tag is available

    <mak:logout actor="student"/>

You can remove (cancel-out, logout) multiple attributes from the session by using `<mak:logout actor="attribute name">` several times and/or by using the star (*) wildcard, e.g.:

    <mak:logout actor="demo_*"/> (attributes whose names start with "demo_")
    <mak:logout actor="*app"/> (attributes whose names end with "app")
    <mak:logout actor="*"/> (all attributes; this "invalidates" the session)

(Later on, logout request might be done in the business logic, with a method `deleteAttributes(param)` that can accept either a String (with optional '*') or a String[]. )

(Later: to accomodate servers that don't do session tracking, login can be done by a query condition rather than by doing a query (once per session) to find an attribute. This way, it won't need to do a query (to check the authentication) at every access, but that condition will make sure that authentication is done. )

`(<mak:object from="best.Student stud" where ="stud.$login()"> ...</mak:object>`
then methodBestSudentLogin("stud") will return "stud.auth.email=$username AND stud.auth.password=$password"
This can be used for http authentication with no session tracking. )

(Later: if an attribute has multiple values, a `choose{AttributeName}.jsp` page is shown. For example, a super user (for that area) can choose to act as any student, Lbg, or company... A student member of more local Vivaldi teams can choose to act for any of the viv teams, etc. )

## Presentation and internal representation summary

This table describes the data types and their default user interface representation. That user interface can be altered with the Presentation language described below. Orientative SQL and Java types are presented.

Data definition type | Default edit user interface | Relational database type (orientative) | Java type (orientative)
--- | --- | --- | ---
type (table) | (list of records, with add, delete, edit controls; titles emphasized) | table |
record | (all fields, as shown below) | record | java.util.Dictionary
int | text field (or slider) | integer | java.lang.Integer
int{} | dropdown choice or radio button
real | text field | double | java.lang.Double
char[] | text field | limited char | java.lang.String
char{} | dropdown choice or radio button
text | text area or file upload | unlimited byte | org.makumba.Text
date | date | date and time | java.util.Date
ptr | dropdown select of record titles. See the example for set/ptr choosers with Makumba. | preferably a long (foreign index) | org.makumba.Pointer
xx=ptr xx->... | (the record, if any) | preferably a long (foreign index) + table
Index field | (nothing) | preferably long, autoincrement, or other unique
creation date modification date | date, not editable | timestamp | java.sql.Timestamp
set | multiple choice of record titles. See the example for set/ptr choosers with Makumba. | table with ptrRel to the parent table and ptr to the foreign table | java.util.Vector of org.makumba.Pointer
xx=set xx-> ... | (like a table, under current record) | table with ptrRel to the parent table, and the rest of the fields |
set int{ ...} | multiple choice from values | table with ptrRel to the parent table, and an int field | java.util.Vector of java.lang.Integer
set char{ ...} | multiple choice from values | table with ptrRel to the parent table, and a char field | java.util.Vector of java.lang.String

## Presentation with JSP taglib

Data can be presented and edited per record and field. The current presentation language uses JSP taglibs and corresponding notation, but principles can be applied in any other HTML-centric presentation language such as PHP.

### Makumba in Java Server Pages

Makumba offers a JSP custom tag library, that allows easy interaction (viewing, editing) with the data in your database, right from your HTML (actually, JSP) document. Since Makumba pages, are essentially JSP pages, a basic understanding of JSP will be helpful to make more advanced use of makumba. Same goes for knowing a bit of Java itself. But you can get a long way with just a few notions! Really.

Makumba tags are written according to Servlet 2.3 specification and JSP 1.1 specification. You will need a so-called "servlet container" that supports them both, such as Apache Tomcat. The corresponding WEB-INF/makumba.tld is already included in the distribution `makumba.jar`. The example WEB-INF/web.xml can be found in Makumba cvs repository.

Before using Makumba tags in your JSP pages you also need to declare the taglib with:

    <%@ taglib uri="http://www.makumba.org/presentation" prefix="mak" %>

A few resources on JSPs (don't be afraid to try first, read later) :

- JSP documentation by Sun
- J2EE web services documentation by Sun. This is an introduction on the various technologies that you might use when building webapplications using Java2 (J2EE).
- Gentle introduction to JSPs

#### Makumba Controller

The makumba controller is a component running in the 'servlet container'. When a request for a makumba page enters the servlet container, the controller will intercept the request, and perform its "controller" activities (cfr. the model-view-controller pattern) :

- checking if the page has the appropriate attributes (see handler initialisation; e.g. force login).
- checking if the page request is the result of a form submit or a deleteLink. If so, perform the relevant actions in the handler and database.
- deal with problems (exceptions) during the controller activity:
  - if `org.makumba.LogicException` is thrown, the Exception can write a message to the `<mak:response>` in the requested page.
  - `org.makumba.UnauthenticatedException` and `org.makumba.UnauthorizedException` will force login (although UnauthorizedException probably shouldn't, bug 444)
  - if another exception occurs, an errorPage will be shown instead of the requested page.

For this to work, the correct configuration must be applied in `WEB-INF/web.xml` (example file). The following would tell the makumba controller to filter all requests for .jsp files.

      <filter>
         <filter-name>makumba_controller</filter-name>
         <filter-class>org.makumba.controller.http.ControllerFilter</filter-class>
      </filter>

      <filter-mapping>
        <filter-name>makumba_controller</filter-name>
        <url-pattern>*.jsp</url-pattern>
      </filter-mapping>

Note that if (in this example) the result page for a makumba form would be an `.html` page, then the makumba controller would not intercept the `.html` page request, and the actions implied by the form, would not be performed.

#### JSP tag parameters

JSP-tag parameter values are either FIXED or RTEXPR (runtime expression). A FIXED tag parameter must have a constant, literal value, while an RTEXPR can also be of the form <%= java_expression %>. On the other hand, some FIXED parameters can contain jsp attributes like $attr in makumba tags.

All parameters are optional unless specifically mentioned as being mandatory.

Specific concern can be the parameter quoting. Tag parameters can be written as name="value" or name='value' (note: the stringLiteral on DATE must be quoted with "). The choice of quote can be determined by the need to use either double or single quote as part of the value itself. If the quote is also present within the value, it must be escaped by a backslash.

      <mak:list from="general.Person p" where="p.gender=\"male\"" >
      <mak:list from="general.Person p" where='p.gender="male"' >
      <mak:list from="general.Person p" where="p.gender='male'" >
      <mak:list from="library.Book b" where="b.publisher=\"O'Reilly\" " >
      <mak:list from="library.Book b" where='b.publisher="O\'Reilly" ' >

Quotes in extra HTML formatting parameters, such as `styleClass`, `title`, `styleId`, `onClick` ... need some special attention with quotes. The parameter values are copied verbatim (with no modifications by makumba) to the resulting HTML, always surrounded with double quotes ("). This means that you have to use other quotes, like single one ('),
If you need to pass a literal backslash (\) you have to escape it with a preceeding backslash (\\).

      <mak:input ... onClick="alert(this.value);"/>
      <mak:input ... onClick="alert('Hello world!');"/>
      <mak:input ... onClick="alert('Hello\\nWorld');"/>

Unfortunately the idea to use a sequence of escapes, eg writing \\\' in the JSP page to set the tag attribute to \', which could be handy for javascript tag attributes, is confusing the Tomcat servlet container.

### <mak:list...>...</mak:list>

Performs a query on the database. The body of the list, if present, is run once for every item in the resulting data (size 0..N), e.g. to display it. Queries are generated on the spot and can be nested.

Example:

    <mak:list from="best.Student s, s.person p" where="p.gender=\"male\""
              orderBy="p.name">

        <c:if test="${mak:count()==1}">
           <p> There are ${mak:maxCount()} male students:
        </c:if>

        <br> <%= counter %>.
        <mak:value expr="p.name"/>
        <mak:value expr="p.surname"/> <br>
        <mak:list from="p.addresses a">
           <mak:value expr="a.streetno"/> <mak:value expr="a.city"/>
        </mak:list>
    </mak:list>

    <c:if test="${mak:lastCount()==0}"> There are no male students. </c:if>

tag parameter | description | comments
--- | --- | ---
`db` | The makumba database to connect to. The format is `Host_SQLEngineType_DatabaseName` If not present, the default database is used. See database configuration and lookup. | Fixed, cannot contain attributes, for now. The default database is chosen if this argument is not set. Can only be set for top-level (root) query tags Can be a Rtexpr <%= ...%>
`from` | OQL FROM section. If the query is nested, the keys from the parent's query are added to this FROM section in the resulting query | Fixed, Mandatory.
`variableFrom` | supplementary, variable OQL FROM section. | Fixed, can contain #{ JSP EL expressions }
`where` | OQL WHERE section. If the query is nested, the WHERE section from the parent's query, is added to this in the resulting query | Fixed, can contain #{ JSP EL expressions }
`groupBy` | OQL GROUP BY section | Fixed, can contain #{ JSP EL expressions }
`(having)` | OQL HAVING section | Fixed
`orderBy` | OQL ORDER BY section | Fixed, can contain #{ JSP EL expressions } `label.$fieldname used to be supported, not anymore`
`offset` | the offset of the result to show (0 for starting from the first result) | Fixed ($attribute allowed). Only allowed for the outermost mak:list
`limit` | the maximum numbers of results to show (-1 for all results) | Fixed ($attribute allowed). Only allowed for the outermost mak:list. LIMIT can limit the query time dramatically, but the children mak:lists are not yet limited.
`countVar` | The `java.lang.Integer` variable that will contain the number of the current iteration. | Fixed. A new Java variable is created, so no other variable by the same name can exist in the Java scope at that point in the JSP. Deprecated, use mak:count() expression language function instead
`maxCountVar` | The `java.lang.Integer` variable that will contain the total number of iterations. | Fixed. A new Java variable is created, so no other variable by the same name can exist in the Java scope at that point in the JSP. Deprecated, use mak:maxCount() expression language function instead
`separator` | Character string as separator between two list elements. It is not included before the first or after the last | D eprecated, use <c:if test="${mak:count<mak:maxCount()}"> instead.
`id` | Tag's identifier | Fixed. Can be used to distinguish otherwise identical tags on a page (to avoid confusion by Makumba's JSP analyser)

#### <mak:object ...>.... </mak:object>

Like list, but the query can only have zero or one result. A zero value for `maxCountVar` and `countVar` indicate that the object does not exist.

Example: See `<mak:list>`.

#### Attributes and OQL in <mak:list > and <mak:object >

Attributes are accessible through `$AttributeName` to any makumba tag. Typically they will be present in OQL sections instead of `$number` attributes (therefore the OQL sections of these tags is not "pure"). For example:

    <mak:list from="best.internal.Lbg"
              where="lbg.country=$country"
              orderBy="lbg.$lbg_order">
      .....
    </mak:list>

If a `$` (dollar) sign needs to be in the string, the escape is `$$`.
If at the end of an attribute there has to be a Java identifier letter, the attribute name can be written as `text1$attrName$text2`, that is, with `$` at both ends.

The http parameters are automatically set as page attributes. Other attributes can be set by the Java code as attributes in any scope (page, request, session, application) using `pageContext.setAttribute(name, value, scope)`.

The query generator is setting all the attributes that are logically possible as prepared query parameters. For example, the $country above is a query parameter since it's a value, but the $lbg_order will not be accepted as query parameter, since it's a field name.

If an attribute has multiple values, it is expanded into multiple OQL parameters. For example:

    <mak:list from="best.internal.Lbg" where="lbg.status in set($status)" >

(For view-level attributes such as lbg_order above, the value range can be defined by :
`<mak:defineAttribute name="lbg_order" values="name, id" default="name"/>` )

(Later: Maybe the page might want to set attributes. Something like :
`<mak:setAttr name="lbg" from="best.internal.Lbg lbg" where ... scope="session" />`
Then the attribute could be used as `$lbg` in the rest of the page/session/application... Con: such stuff is normally done by the Java code. )

#### <mak:value .../>

Displays the value of an expression from within the query.

Example:

    <mak:list from="best.Student s, s.person p"
    	where="p.gender=\"male\"" orderBy="p.name">
        <mak:value expr="p.name"/>
        <mak:value expr="p.surname"/>
        <mak:value expr="p.birthdate" var="birth" printVar="printBirth"/>
        <% // we only print the birthdate if it's after some date
             if ( ((java.util.Date)birth).after(new java.util.Date(1980, 0, 1)) )
                 out.print(printBirth);
        %>
        <mak:value expr="s.person.favoriteQuote" maxLength="60" addTitle="auto" />
    </mak:list>

tag parameter | description | comments
--- | --- | ---
`expr` | OQL SELECT projection expression. It will be displayed if `var` nor `printVar` are not specified. | Fixed, Mandatory.
`var` | The value of the expression is set to a new `java.lang.Object` variable by this name, as well as to a page-scope attribute, also by the same name (accessible as `$attributename`). | Fixed. A new Java variable is created, so no other variable by the same name can exist in the Java scope at that point in the JSP. Note: the Java variable must be cast to its specific type (Integer, String, Date, Text, Pointer, Vector) before using it as such.
`printVar` | The formatted output as it would have been printed, is instead stored in a new `java.lang.String` variable by this name, as well as to a page-scope attribute by the same name (accessible as `$attributename`). | Fixed. A new Java variable is created, so no other variable by the same name can exist in the Java scope at that point in the JSP.
`urlEncode` | Indicates if the expression will be part of an URL or not. If "true", the output is URL-encoded. Default is "false". | Rtexpr.
`html` | Normal behaviour is to transform character output to its HTML escaped form. If this is "`true`", content is assumed to be HTML, and is not escaped. If "`auto`", heuristically checks the content for HTML tags and inhibits escape if there are any. Default is "`false`". | Rtexpr. Only char[] and text
`format` | Format string to specify the formatting of a date value, according to `java.text.SimpleDateFormat` | Rtexpr. Only for date. Defaults to "`dd MMMM yyyy`"
`lineSeparator` | Separator for long lines. If a text consists of short lines only, it will be surrounded by `<pre>...</pre>`. Default is "`<p>`". | Rtexpr. Only for text. Current implementation is buggy: separator is added before every long line, instead of between every long line.
`longLineLength` | The length of a long line. If a text contains long lines, it will be printed differently. See `lineSeparator`. Default is "30" | Rtexpr. Only for text.
`maxLength` | The maximum length (number of characters) to print. Longer output is cut off, and an `ellipsis` is added to indicate the cut. If not set (default), there is no maximum. | Rtexpr. Only applies for char[] AND if it is not already HTML formatted (cfr. `html`).
`ellipsis` | The character string to print to indicate that the text extended the `maxLength`. Default is "...". The final printed string, including the `ellipsis`, will not exceed `maxLength`. | Rtexpr
`ellipsisLength` | The equivalent character length of `ellipsis`. By default, this is the number of characters in `ellipsis`. But if `ellipsis` is e.g. HTML code, then that is not appropriate. | Rtexpr. Example, the ellipsis is an image of approx 3 characters wide. `ellipsis="<img src=icon.gif width=10 height=10>" ellipsisLength="3"`
`addTitle` | If "`true`", add an HTML tooltip with the value, to the printed output. If "`auto`", add tooltip only if the printed output is cut (cfr `maxLength`). Default is "`false`". | Rtexpr. Note: implementated by producing as output: `<span title="printVar">possibly-cut-printVar</span>`
`default` | The character string to print if the `expr` results in a NULL value. Default is `default=""` (i.e. zero-length string) Support not available for: date, "choice" = ptr, set, setCharEnum | Rtexpr
`empty` | The character string to print if the normal printed output would be empty (i.e. zero-length string). Therefore, this is also used for case `expr=NULL` and `default=""`. | Rtexpr

#### mak:count(), mak:maxCount(), mak:lastCount()

These are JSP EL (expression language) functions that give information about the iterations in a list.

- mak:count() gives the number of the current iteration inside a mak:list or mak:object. It has no value outside that tag.
- mak:maxCount() gives the total number of iterations inside a mak:list or mak:object (1). It has no value outside that tag.
- mak:lastCount() gives the total number of iterations of the previous mak:list or mak:object, respectively. It has no value inside the mak:list/object.
  Note: if you want to store the value of some mak:list/object for usage in/after a later mak:list/object, you can do that with <c:set var="someVariableName" value="${mak:lastCount()}" just after that mak:list/object.

Example using the Java Standard Tag Library (JSTL, prefix "c"):

    <mak:list ...>
       <c:if test="${mak:count()==1}">These are the list elements: </c:if>
       <tr bgcolor="${mak:count()%2==1?"white":"grey"}">
           <td>this shows in alternative colors</td>
       ...
       <c:if test="${mak:count()!=mak:maxCount()}">
           a separator where we can have any <b>tag</b>
           we don't want separators to be shown after the last element
       </c:if>
    </mak:list>
    <c:if test="${mak:lastCount()==0}">These are no elements </c:if>

#### <mak:if ...> ... </mak:if>

Displays the body of the tag only if the OQL expression evaluates to true.

Example :

    <mak:list from="best.Student s"
    	  where="s.person.birthdate <> nil" orderBy="s.name">
       <mak:value expr="s.person.name"/>
       <mak:if test="s.person.hideAge = 0">
          was born on <mak:value expr="s.person.birthdate" />
       </mak:if>
    </mak:list>

tag parameter | description | comments
--- | --- | ---
`test` | OQL SELECT projection expression. It must be a test, resulting in a 'boolean' in SQL : 0 or 1. for the test expressions: =, !=, <, <=, >, >= | Fixed, Mandatory. (in first implementation, this was called `expr`, but changed to reflect practice in XSL and JSTL)

#### <mak:attribute .../>

Displays the value of an attribute, or sets it to a Java variable.

Example:

    <mak:attribute name="pattern" var="pattern" exceptionVar="exception"/>

    <% if (exception!=null) {
         pageContext.setAttribute("pattern", (String)pattern+"%");
    %>
       <mak:list from="type t" where="t.field like $pattern" >...</mak:list>

    <% } else { %>
       No pattern argument. Please indicate one.
    <% } %>

tag parameter | description | comments
--- | --- | ---
`name` | the name of the attribute. Will be printed if `var` is not present and there is no exception when finding the argument. If there is an exception but `exceptionVar` is indicated, nothing will be printed. | Fixed, Mandatory.
`var` | The name of the `java.lang.Object` variable where to store the attribute value. Note that you will have to cast it to its specific type. | Fixed
`exceptionVar` | The name of the created `java.lang.Throwable` variable that will hold eventual exceptions raised when trying to compute the attribute. If `exceptionVar` is missing, any raised exception will stop page execution. If it is present, and `AttibuteNotFoundException` occurs, the attribute is set to `null` (so a next request for the attribute will return `null`) | Fixed
`db` | The database in which the business logic (if any) will compute the attribute. The default database is normally used. | Fixed

### Forms

Makumba can produce four types of forms: new, add, edit and generic forms.

All forms have a number of common features: They can include `<mak:input >` tags. They all can have "`action`", "`method`", "`handler`", "`name`" and "`message`" arguments.

Handler methods (if they exist) are executed by the makumba controller, when the form is submitted to another makumba page.

Non-generic (type specific) forms
New, edit and add forms are type specific. Their fields must be named after the fields in the respective type (and related fields).

If there is a business logic class, the engine will look (once after each page compilation) for the corresponding handler method. The handler methods are executed before the default action and may prevent the action from being executed by throwing an exception. Some forms also have an after-action handler method.

If the handler class exists but no handler method can be found, an error is thrown (the site is not allowed to do the operation, e.g. StudentHandler will never have a on_newLibraryBook() method). If the handler class wishes to allow the action, it can define an empty handler method.

Multiple forms
- addForms can add to the subsets of object produced by the enclosing newForm.
- any number of levels of form inclusion is possible but only the outermost form can have an action, onSubmit, and method and other attributes specific to HTML forms.
- all form actions take place in a single transaction, which is rolled back by the controller filter if there is an error.
- after_ methods are not executed in correct order (bug 689)

    <mak:form action="blabla">
    <%-- the topmost form, will result in a HTML form, may or may not have logic,
         or it can be a specialized form (new, edit, add...)
    --%>

      <mak:input name="first" /> <%-- the topmost form can have fields of its own --%>

    <mak:list .... >
      <mak:addForm object="bla" field="bla" >
      <%-- note that there is no action indicated here, it's the action of the
           topmost form a normal on_add BL method will be called
       --%>
         <mak:input name="second" /><%-- the topmost form can have fields of its own,
                                         even repeated in loops
                                    --%>
         ...
      </mak:addForm>
    </mak:list>

    <mak:list .... > <%-- there can be more than one loop in a root form -- %>
    ...
    </mak:list>
    <input type=submit> <%-- it's easy to add a submit button anywhere --%>
    </mak:form>

(Later, new and edit forms that have no body, will build default forms. )

#### <mak:newForm ...>.... </mak:newForm>

Makes a form for creating a new object of the indicated type.

Example (personNew.jsp):

    <mak:newForm type="general.Person" action="personList.jsp" method="post">
            <mak:input name="name"/>
            <mak:input name="surname"/>
            <input type="submit">
    </mak:newForm>

tag parameter | description | comments
--- | --- | ---
`type` | Makumba type for record creation, or OQL label for subrecord creation | Fixed, mandatory.
`(handler)` | the Java class.method that handles the response | defaults to on_new+NameOfMakumbaType. Arguments: (Dictionary newData, Attributes a, Database db)
`action` | the response page of the form | Mandatory if a <mak:action> is absent
`method` | the HTTP method (`get` or `post`) | Defaults to `get`
`name` | the name of the created object in the response page | Fixed. Defaults to __mak__edited__. If set, it is also used for the name of the html form (`<form name="..." ...>`)
`message` | the message that is displayed in the response page upon success | Fixed. Defaults to "changes done".
`target` | Form-specific html tag attributes | The content is copied to the resulting `<form...>` tag. Careful with (escaping) quotes.
`onReset`
`onSubmit`
`styleId` | Generic HTML tag attributes. | results in `id="..."`
`styleClass` | results in `class="..."`
`style` | The content is copied to the resulting html tags. Careful with (escaping) quotes.
`title`
`onClick`
`onDblClick`
`onKeyDown`
`onKeyUp`
`onKeyPress`
`onMouseDown`
`onMouseUp`
`onMouseMove`
`onMouseOut`
`onMouseOver`

At form response, makumba (controller) invokes the following methods:

1. By defining `on_new*`, the handler class gets the opportunity to validate/change the data. If the data is not correct, the handler can throw an exception to prevent insertion in database.

       handler.on_newTypeName(data, attr, db);

2. The standard Database call for insertion:

       Pointer created= db.insert(type, data);

3. By defining `after_new*`, the handler class gets the opportunity to do supplementary operations with the inserted record.

       handler.after_newTypeName(created, data, attr, db);

argument | Java type | comments
--- | --- | ---
`data` | `java.util.Dictionary` | The new record to create. It is read from the HTTP query string by interpreting the form.
`attr` | `org.makumba.Attributes` | Other attributes in the page (sent as HTTP arguments or present in the HTTP session).
`db` | `org.makumba.Database` | The database where the record will be inserted
`created` | `org.makumba.Pointer` | The pointer to the created record. Only for `after_new`

If the handler class is present but both handler methods are missing (`on_new` and `after_new`), the action is not allowed.

At response the following calls are executed (in this order):

    PersonLogic handler_obj; // see handler discovery
    handler_obj.checkAttributes(attr, db);
    handler_obj.on_newGeneralPerson(data, attr, db);
    Pointer created= db.insert("general.Person", data);
    handler_obj.after_newGeneralPerson(created, data, attr, db);

#### <mak:addForm ...>.... </mak:addForm>

Makes a form for creating a sub-object of the mandatory enclosing `<mak:object>` (e.g. a language of a student, an address for a person).

Example:

    <mak:object from="best.Student s" where="s=$student">
        <mak:addForm object="s" field="languages"
        		 action="studentView.jsp" method="post">
            <mak:value expr="s.name"/>
            <mak:input name="level"/>
            <mak:input name="comments"/>
        </mak:addForm>
    </mak:object>

tag parameter | description | comments
--- | --- | ---
`object` | The label of the object whose sub-object will be created | Fixed, mandatory
`field` | The field name that denotes the sub-object. | Fixed, mandatory.
`(handler)` | the Java class.method that handles the response | defaults to `on_add+MakumbaType+fieldname`. Arguments: `(Pointer baseObject, Dictionary newData, Attributes a, Database db)`
`action` | see `newForm`
`method`
`name`
`message`
`target` | Form-specific html tag attributes, see `newForm`
`onReset`
`onSubmit`
`styleId` | Generic html tag attributes, see `newForm`
`styleClass`
`style`
`title`
`onClick`
`onDblClick`
`onKeyDown`
`onKeyUp`
`onKeyPress`
`onMouseDown`
`onMouseUp`
`onMouseMove`
`onMouseOut`
`onMouseOver`

This will call the handler methods: (the argument names are adapted to the example. Note the changed pointer argument in the methods.)

    on_addBestStudentLang(Pointer student, Dictionary languageData, Attributes pageParams, Database db)
    after_addBestStudentLang(Pointer address, Dictionary languageData, Attributes pageParams, Database db)

#### <mak:editForm ...>.... </mak:editForm>

Makes a form for editing the object indicated by any of the labels of the mandatory enclosing `<mak:object>` or `<mak:list>`. Also linked objects can be edited through the same form.

Example:

    <mak:object from="best.Student s, s.person p" where="s=$student">
        <mak:editForm object="s" action="studentView.jsp" method="post">
            <mak:input name="person.name"/>
            <mak:input name="person.surname"/>
            <mak:input name="graduated"/>
        </mak:editForm>
    </mak:object>

tag parameter | description | comments
--- | --- | ---
`object` | The label of the OQL object to edit | Fixed, mandatory.
`(handler)` | the Java class.method that handles the response | defaults to `on_edit+MakumbaTypeOfEditedObject`. Arguments: `(Pointer object, Dictionary changedFields, Attributes a, Database db)`
`action` | see `newForm`
`method`
`name`
`message`
`target` | Form-specific html tag attributes, see `newForm`
`onReset`
`onSubmit`
`styleId` | Generic html tag attributes, see `newForm`
`styleClass`
`style`
`title`
`onClick`
`onDblClick`
`onKeyDown`
`onKeyUp`
`onKeyPress`
`onMouseDown`
`onMouseUp`
`onMouseMove`
`onMouseOut`
`onMouseOver`

The response will call the handler method: (the argument names are adapted to the example)

    on_editBestStudent(Pointer student, Dictionary fieldsToChange, Attributes pageParams, Database db)

#### <mak:form ...>....</mak:form>

Creates a generic form, that may call a handler method in response. It allows the JSP author to make any kind of form. They are suitable for more complex operations than new, add, edit.

Example:

    <mak:object from="best.Student s" where="s=$student">
        <mak:form handler="doSomething" action="studentView.jsp" method="post">
            <mak:input name="xxx" value="s.person.name"/>
            <input type=submit>
        </mak:form>
    </mak:object>

tag parameter | description | comments
--- | --- | ---
`handler` | the Java method that handles the response | Arguments: `(Dictionary formFields, Attributes restOfArguments, Database db)` Not mandatory. A form without handler will simply set attributes (as makumba objects) for the next page
`action` | see `newForm`
`method`
`name`
`message`
`target` | Form-specific html tag attributes, see `newForm`
`onReset`
`onSubmit`
`styleId` | Generic html tag attributes, see `newForm`
`styleClass`
`style`
`title`
`onClick`
`onDblClick`
`onKeyDown`
`onKeyUp`
`onKeyPress`
`onMouseDown`
`onMouseUp`
`onMouseMove`
`onMouseOut`
`onMouseOver`

#### <mak:input... />

An input field to be created, depending on the makumba type of the field. See the example for set/ptr choosers with Makumba.

scripts/makumba-javascript.html

The difference between `<mak:input >` and normal HTML `<input>` in a makumba form are:

- `<mak:input>` produces objects prepared for setting/comparing makumba fields (e.g. Pointer, Date, Text).
- the fields produced by `<input>` will be available as page $attributes but will all be of type String
- the fields produced by `<mak:input>` are available separately as a Dictionary to the handler method

    <mak:object from="best.Student s, s.person p" where="s=$student">
        <mak:editForm object="p" action="studentView.jsp" method="post">
            name      <mak:input name="name"/>
            surname   <mak:input name="surname"/>
            gender    <mak:input name="gender" type="tickbox" />
            dob       <mak:input name="birthdate" format="yyyy-MM-dd" />
        </mak:editForm>
    </mak:object>

tag parameter | description | comments
--- | --- | ---
`name` `(or field)` | Makumba field (from the edited record or via base pointers or sub-record pointers) | Fixed, mandatory
`nameVar` | The name of the java variable in which to store the name of the HTML input. In multiple forms, there may be more HTML inputs generated by one mak:input, so a suffix is added by makumba to the name to generate unique names for each. | Fixed
`value` | OQL expression relative to enclosing query tags or a `$attribute` computed previously in the page (with `<mak:value var=.../>` or `pageContext.setAttribute(...)`), or read by in the previous page by an `<mak:input />` | Fixed
`type` | HTML INPUT type to be used "`hidden`" works for all fields for `char[]` , type can be "`text`" or "`password`", default is "`text`" default type for `[set]intEnum`, `[set]charEnum`, `ptr` and `set` is "`select`" (dropdown or scroll list depending on `size`). Alternative is "`tickbox`" (checkboxes or radio buttons) `date` is splitted in 3 inputs, `<fieldname>_0` (day), `_1` (month), `_2` (year), and likewise for `time` elements for `text`, default is "`textarea`"; "`file`" will create file upload box, and will create supplementary attributes `<fieldname>_filename`, `<fieldname>_contentType` and `<fieldname>_contentLength` that have to be handled separately by the handler method | Fixed
`display` | If "`false`", it will not show the <input> but it will expect to read it in the next page. This allows the page designer to format the input control manually | Rtexpr.
`dataType` | The makumba type of the data (needed if there is no value, no default expression for the value, or no makumba type associated with an attribute) | Fixed. Can be `char, char[xx], int, date, text, ptr Type, set Type`
`format` | Format string, according to java.text.SimpleDateFormat Can only countain `d, M, y, H, m, s` formatting chars, and any kind of separators. Ex: `'the day' dd 'of the month' MMMM 'in the year' yyyy`. Default is "`dd MMMM yyyy`" | Rtexpr. Only for date.
`size` | Size of the input control | Rtexpr. Only for `char[]`, `int` (size of the textbox) and `set`, `ptr` (height of the select)
`maxLength` | Max length of a text control | Rtexpr. Only for `char[]` and `int`. Defaults to makumba width of the `char[]`
`labelSeparator` | The string that separates the tickbox (radio/check) from the label. Default is `" "` (space). The output will be `< tick >< labelSeparator >< label >` | Rtexpr. Only for `type="tickbox"`.
`elementSeparator` | The string that separates the different options. Default is `" "` (space). The output will be `< [x] label >< elementSeparator >< [x] label >` | Rtexpr. Only for `type="tickbox"`.
`(elementSeparatorList)` | The list of strings that separates the different options. Not active by default. The format is "`!sep[1]!sep[2]!...!sep[n]!`" where any character (not appearing inside the separators) can be used as delimiter, e.g. '!'. The output will be `< [x] label >< sep[1] >< [x] label >< sep[2] > ... < [x] label >< sep[n] >< [x] label >< sep[1] > ...` | Rtexpr. Only for `type="tickbox"`. Overrides `elementSeparator` if it exists.
`rows, cols` | Number of textarea rows and columns | only for `text`
`default` | FIXME | Rtexpr
`empty` | FIXME | Rtexpr
`styleId` | Generic html tag attributes, see `newForm`
`styleClass`
`style`
`title`
`onClick`
`onDblClick`
`onKeyDown`
`onKeyUp`
`onKeyPress`
`onMouseDown`
`onMouseUp`
`onMouseMove`
`onMouseOut`
`onMouseOver`

Fields of related records can be reference and edited as well, via pointers. In this (somewhat strange) example, one can edit the name of the capital city of the country of which person is a citizen, through the person edit form :

    <mak:input name="person.citizenship.capital.name" />

Restrictions for different field types:

- fixed fields: cannot be edited
- relational and index pointer: cannot be edited
- timestamps (create and modify): cannot be edited
- subset, subpointer: cannot be edited as a field, only as a separate object

##### <mak:option....>...</mak:option>

By default, for pointer and set fields, `mak:input` will show a choser (selector) that includes the title of all possible options, ordered by that title. To change that behavior, the `mak:input` can include one or more `mak:option`. Options can be repeated using `mak:list`, `c:foreach`, and in general can appear inside any other tag.

Text inside `mak:option` will become an option title. The `value` attribute will become the option. All text produced inside the mak:input that is not inside a mak:option must be blank!

If `mak:option` doesn't have a value indicated, it will produce a nil option. Such nil options will be ignored at form submission.

If an option value appears many times it will only be shown the first time it occurs.

    <mak:input name="some" dataType="ptr T">
    <mak:option>Please choose:</mak:option>
    <mak:list from="T choice" where="someCondition" >
        <mak:option value="choice"><mak:value expr="choice.someField" /></mak:option>
    </mak:list>
    <mak:option> -------- separator----------</mak:option>
    <mak:list from="T choice" where="someOtherCondition" >
       <mak:option value="choice"> <mak:value expr="choice.someField /></mak:option>
    </mak:list>
    </mak:input>

tag parameter | description | comments
--- | --- | ---
`value` | Value of the option, can be an OQL expression or a $attribute | Fixed, if not indicated, nil (null option) is default

#### <mak:action>....</mak:action>

If the action URI of a form or deleteLink is more complex, possibly including other makumba tags, the action parameter of the form tag can be omitted, and the action URI can be indicated in a `mak:action`, anywhere inside the form tag.

Example:

    <mak:editForm object="ins" method="post">
      <mak:action>memberView.jsp?person=<mak:value expr="p"/></mak:action>
    ...
    </mak:editForm>

### <mak:deleteLink>...</mak:deleteLink>

Produces a link to the page that will delete the object indicated by any of the labels of the mandatory enclosing `<mak:object>` or `<mak:list>`

Example:

    <mak:object from="best.Student s, s.languages l"
    	    where="s=$student AND l.lang.name=$langname">
    	<mak:deleteLink object="l"  action="studentView.jsp">
    		Delete <mak:value expr="l.lang.name"/>
    	</mak:deleteLink>
    </mak:object>

tag parameter | description | comments
--- | --- | ---
`object` | OQL label of the object to delete | Fixed
`(handler)` | the Java class.method that handles the response | defaults to `on_delete+MakumbaTypeOfEditedObject`. Arguments: `(Pointer object, Attributes a, Database db)`
`action` | see `newForm`
`message`
`target`
`name`
`styleId` | Generic html tag attributes, see `newForm`
`styleClass`
`style`
`title`
`onClick`
`onDblClick`
`onKeyDown`
`onKeyUp`
`onKeyPress`
`onMouseDown`
`onMouseUp`
`onMouseMove`
`onMouseOut`
`onMouseOver`

The response will call the handler method: (the argument names are adapted to the example)

    on_deleteBestStudentLang(Pointer lang, Attributes pageParams, Database db)

### <mak:response/>

`<mak:response/>` prints information about the results of the actions that were performed by the makumba controller (e.g. for a form submit or deleteLink): It either displays the `message="..."` parameter of the form tag (in green) in case of success, or (in red) the message of a uncaught `LogicException` resulting from Business Logic. Other exception types will provoke an exception page.

The unformatted message is available as request-scope attribute `makumba.response`. The jsp page can get hold of the message using e.g.

    <% String s = (String) request.getAttribute("makumba.response") %>

Similarly, request-scope attribute `makumba.successfulResponse` is set only in case of successful action execution.

    <% if (null == request.getAttribute("makumba.successfulResponse")) { /* action failed */ } %>

(A body-tag style (`<mak:response>...</mak:response>`) will be added later, to display different messages for different circumstances (errors). It will also be possible to get hold of the actual exception object. )